Togo or not Togo (Le Poulpe t. 254) (French Edition)

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A possible strapline for the vision could be: Establishing the organization as a recognized body 5. The current members emphasized the need for this body to be legally recognized to permit or support them to play a full role as a member. It was proposed that FAO be requested to provide the support in the drafting of the legal constitution of the organization. This constitution should include the formal rules for the membership, including the rules for the election of the future board and Executive Committee and the terms of reference of such board.

Confirming the vision, mission and plans to achieve the vision 6. The members requested clarity in the services they would receive and how this would work. This new draft vision has been simply articulated and proposes some of the key services and support needed in terms of dissemination of best practice. Rapidly developing the Web site 7. The members reported that a key step agreed in past meetings had been the creation of a Web site to showcase best practice. The Executive Committee proposed the setting up of a working group to develop a pilot Web site based on the design of the existing Web page to host the presentations and reports presented at the Seychelles meeting and, where records exist, the material from the previous meetings.

It is also recommended that this group should then create a proposal that will specify and cost the development of a fully functional Web site. Creation of a marketing and communication plan 8. The members noted that regular communication was lacking. The Executive Committee discussed this issue and proposed the creation of a communication and dissemination plan that would market the benefits of the network organization.

This would provide agreed statements on the network vision, example of projects and current actions to target stakeholders. The defined benefits for countries and members of the network would be articulated by the information created by this group for use by the members. This group may lead the development of publications for journals, the Web site and standard information similar to the Fish Inspector but focused on African fish technology and market access issues.

Review of the business plan and funding support for the next phase 9. The members requested clarity on the operational planning and necessary budget. The Executive Committee proposed that the current business plan be updated using this roadmap and that a concept note, which could assist the group, be created for consideration by FAO.

Much effort was put into the research activities presented, but it was recommended again, as in , that due consideration be given to the cost—benefit analysis of techniques developed in research. The Secretariat should provide guidance for future research work to be presented to the experts. In order to celebrate excellence and encourage the experts in their efforts in sustaining the Expert Meeting through applied research and development initiatives, the Secretariat should explore the possibility of instituting an award in whatever form: Live and fresh fish handling and preservation However, there are some challenges that need to be addressed in relation to: The programme should continue with implementation of the planned activities, which include: There is a need to link it with other programmes in the region for synergies and complementarities and take into consideration other ideas raised at the FAO meeting.

A presentation on the effect of bleeding on the keeping quality of farmed catfish Clarias gariepinus in Uganda was discussed. A seminar was presented on refrigeration as applied to seafood — recent developments and applications. Trends indicate that the technology is growing very fast as a function of expanding international marketing of fish and aquaculture products, associated with stringent quality assurance demands. The pro and cons of applying different refrigeration techniques, such as chilling-icing, super chilling, glazing technology, brine freezing, blast air freezing, plate freezing, freezing under electric field or electro-freezing, as well as the high-pressure processing technique, were thoroughly discussed.

Participants agreed unanimously that refrigeration technology was important for fish preservation and was critical in expanding fish trade. However, it was noted that adoption of some of these techniques could be difficult in the African context, especially due to cost implications. Nevertheless, the need for developing institutional capacity to meet the recent refrigeration challenges was underscored. Thus, it was recommended that the practicability of the various refrigeration techniques should be explored further. Similarly, the establishment of partnerships and collaboration between institutions in the regions was emphasized in order to examine the use of refrigeration technologies using solar energy, a readily available resource, in the region.

Fish processing, value addition and nutrition Smoking of fish as an effective method to add value, reduce post-harvest losses and diversify products offered to consumers was underscored, especially in countries where this technique is being assessed for introduction. Any further work in these countries should take into account existing techniques and consider the x economics, cost—benefit analysis; following key factors for a successful outcome: One such requirement is to meet emerging European Union EU regulations on cured fish in and This situation will require efforts to improve traditional fish processing techniques in the region.

Noting the trend, and under an FAO-sponsored programme, the Institute of Technological Research in Senegal has developed an improved smoking system named the FAO-Thiaroye system aimed at controlling the concentration of PAHs in smoked fish and, thus, improving the safety of final products. This will facilitate access to international markets, such as the EU, and also protect domestic consumers. Participants acknowledged the cost-effectiveness and suitability of the technology to small-scale fisheries and noted the positive initial laboratory test results.

This should also be complemented by a study of PAH-producing characteristics of the major tree species used for smoking in the region. The heating unit of the FAO-Thiaroye smoker has also been shown to be effective as a mechanical drier. In order to curb the high post-harvest losses in natural drying processes during rainy seasons, the participants recommended that this all-weather drying technique be disseminated for adoption in the region. In considering the environmental threat through deforestation by using charcoal, participants recommended that alternative sources of energy should be investigated.

The dryer has been validated for shrimps with a payback after 15 production cycles of kg. Participants recommended that further trials should be done on other fish species.

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Considering the nutritional composition of fish — proteins, micronutrients an exclusive source of certain minerals , polyunsaturated fatty acids — and the scientifically established role of omega-3 fatty acids in the prevention of certain diseases coronary heart disease and in child brain development, the study on micronutrient enrichment of meals using simple technology provides a significant contribution to food and nutrition security, adding value to local meals and low-value fish.

The approach to nutrition should be an integral part of any development programme. For this purpose, a linkage should be established with key agencies involved in food and nutrition security, such as FAO, WHO and WFP, and various other stakeholders e. An IQ assessment should be conducted to show if there are other benefits of micronutrient enrichment of meals for children.

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Other recommendations on the micronutrient enrichment study were: It was generally acknowledged that promoting an increased consumption of fish within a static wild capture scenario requires efforts in aquaculture development, post-harvest loss reduction and promotion of the use of low-value fish species and bycatch for direct human consumption, and it was recommended that these issues should continue to be key areas for future research activities in Africa. The cluster-based Camdeboo Satellite Aquaculture Project in South Africa uses farmed catfish to produce sterilized products in pouches for the food service sector.

Meals made from pouched products had x creating self-employment opportunities for women, contributing to economic growth through high consumer acceptance ratings. The approach demonstrated the potential for: The strategic business plan of this project could be considered for use as an example for similar studies.

To maximize the benefits and to reduce the impact on the environment, a recommendation was made to explore further the utilization of by-products from processing the farmed catfish, affording further income opportunities from the farmed fish. The study on press oil extraction was an interesting approach to adding value to low-value and underutilized fish and utilizing the by-products from processing.

The press was developed at a low cost EUR The production of oil and of flavouring cubes from the press cake followed a simple process and the products were well accepted by the consumers. To market the products effectively, it was recommended that there would be a need for the development of adequate packaging and labelling for the products, especially the flavouring cube. The challenge of maximizing utilization of bycatch, especially in inshore shrimp trawling, was discussed. Experience from the United Republic of Tanzania suggests that bycatch continues to form a high percentage of catches in the shrimp fishery despite the institution of various selective catching measures.

In the case of the United Republic of Tanzania, effort has been made to promote bycatch utilization by using different value-addition methods. The result from both of these initiatives suggests that it is possible to maximize utilization of bycatch through economically viable value-addition initiatives. Participants recommended that these initiatives should be promoted, focusing on dissemination of the results to key players, including communities and owners of shrimp trawlers. In this regard, there is a need to strengthen training programmes aimed at building the capacity of community members and extension workers to participate in production of proven bycatch products.

As mentioned in the preceding paragraph, the industrial fish sector should be made aware of the findings so that it can be persuaded to participate in this initiative as part of rational recuperation of the resource rent it generates from the fishery. Results from experiments conducted in Senegal on cottage production of marinated and semi-preserved shellfish were presented and discussed.

The method applied was found to have the potential to enable smallholder women to access more-lucrative markets. Considering that shellfish collection in Africa is mostly done by women, such improvements have great potential to contribute to improved socio-economic livelihood in communities, in addition to potentially decreasing the pressure on resources. However, a successful and sustainable implementation requires the development of the business management skills of the operators.

It was strongly recommended that the study should continue in order to perfect the value-addition method and integrate marketing strategies, resource management issues, and attractive packaging methods in order to make it economically viable among target groups, especially rural women.

Fish safety and quality A peer-reviewed new method of histamine analysis was presented and discussed. This method has been acknowledged and rewarded at several scientific fora as a method that is accurate, has low detection levels and shows improved reproducibility. The study conducted on swordfish caught in the Western Indian Ocean Seychelles Exclusive Economic Zone [EEZ] has provided preliminary information relating to the levels of total mercury in swordfish of varying fish sizes.

The results were comparable with previous studies in other parts of the world. There is a need to continue with the study, putting more focus on fish of 10 kg and above and having a smaller interval of different weight categories. FAO will monitor the findings of these studies and provide guidance on their implementation, which might include a possible introduction of a maximum weight limit for swordfish export. Socio-economic, marketing and market access issues The report on challenges to small-scale fish exports outlined the importance of fish exports to sub-Saharan Africa, even though the region is a relatively small player in the world fish export markets.

This sector, however, faces serious challenges especially because of constraints faced by the exporting countries in meeting the stringent quality control and sanitary conditions of importing nations and the different requirements and approaches of various certification bodies for ecolabelling schemes. The experience by the Naturland certification process in Lake Victoria has provided a good example of how an inclusive approach, bringing in the private sector, private—public partnerships and beach management units and including the social dimensions in an ecolabelling initiative, can deliver results.

There is also a need for better data collection to bring out the true value of intraregional trade in small-scale fisheries, which has been underestimated owing to a lack of adequate information. The case study conducted in Senegal on the octopus value chain has brought out the role of different players, the revenues accrued in the system, and conflicts between the fishers and intermediaries.

It has revealed that post-capture handling of octopus does not affect octopus prices and is not considered a major problem by the market based on very low reject levels. There is, however, a need for more accurate baseline information, which should also bring out more clearly the role of women and how they can benefit from the octopus fishery.

Past interventions have concentrated on the supply side, which has been a weakness in development of the industry, and on attempts to improve the welfare of the fishing community. There is a need for interventions focused on improving market access for fishers alongside formulation of better conservation measures. The study on the sun-dried Lake Victoria sardine value chain in Uganda has identified the key players in the Lake Victoria sardine value chain, margins from trade and the significant role of regional trade, feed manufacturing and supermarkets in driving the Lake Victoria sardine industry.

It has also identified the main constraints, including seasonality, high input costs, inappropriate handling facilities, lack of knowledge and skills, unreliable markets, insufficient market information, inadequate extension and unfavourable credit markets, among others. However, there are many opportunities for advancing the sardine trade, including low fishing labour costs, abundant fish stocks, presence of Beach Management Units BMUs , insatiable and diverse regional markets, favourable government and regional policies. For development of the industry, a number of interventions will need to be undertaken, including: In addition, there is a great need for regional cooperation among respective inspection services and border-post agencies and a detailed study across the ECA region to gain a better understanding of Lake Victoria sardine value chains and creation of market platforms for chain actors.

Women in Tunisia participate in various economic activities as sources of income to support their livelihoods, including the collection of clams. In spite of the fact that both men and women participate in this business, men have been responsible for marketing the products while women remain mainly as collectors of clams.

Participants noted the findings and it was recommended that arrangements should be made to institutionalize the clam collection groups to improve their autonomy and bargaining power for a better profit-sharing environments. Findings from interventions made on sardine utilization in Uganda indicated that East African countries are experiencing high post-harvest losses as a result of a lack of skilled fishers, weakness in law enforcement, illegal fishing gear and practices, which partly accounted for harvest of immature fish coupled with limited capacity to land high catches.

It was further stipulated that harmonization of mesh size and shifting fishing activities away from the shoreline should be adopted as some of the measures to protect juvenile fish. Participants noted the findings and recommended that experience from similar interventions in countries such as Mozambique by using solar dryers and application of a range of value-addition techniques be considered for improved sardine utilization. Furthermore, participants recommended that regional cooperation on management and marketing of Lake Victoria sardine was a priority and that this should involve people at the grassroots level producers, fishers, etc.

It was noted that problems in small-scale fisheries SSFs are mostly organizational rather than technical. Similarly, there was agreement that poor extension services are a real constraint on disseminating innovations from research institutions aimed at addressing challenges faced by small-scale fishers in Africa.

In view of this situation, it was strongly recommended that efforts should be made to establish a regional training programme aimed at providing extension training for fisheries extension workers. Potential trainees should be drawn from strategic public services, non-governmental organizations NGOs and other private institutions across the region.

The experience gained from previous regional training programmes, such as the one conducted under the Ghana—Netherlands artisanal fish processing project, should be considered during development of the proposed programme. Mozambique presented training manuals, posters and leaflets as well as practical methods corporal expressions, video, drawings, photos for training of trainers, technicians and small-scale fisheries communities in order to train other members of fishing communities on hygiene, the Hazard Analysis and Critical Control Point HACCP system, traceability and best practice in preservation methods icing, safety in the market, aquaculture, etc.

The need for preparing pictorial training material for on-site and distance training in small-scale fisheries was discussed. The meeting recommended that a concerted effort should be made to develop further the material to respond to a large demand for this type of training. Case studies from Indonesia demonstrated key problems in the value chain: The trade corridor approach would mitigate these problems, problems that face many African countries.

It was therefore strongly recommended that East African nations should consider forming trade corridors and piloting the approach including the participation of the export associations, artisanal suppliers and the government. The existence of a strong Ugandan Fish Processors and Exporters Association UFPEA and a regional export association, in an alliance with inspectors and government officials, would make the trade corridor approach useful.

The project received support from the International Labour Organization to implement a pilot phase limited to Lake Victoria in June —May ; and, subsequently, the EU supported an up-scaled phase covering the entire country as from March The project has achieved an increase in fish prices, reduction in post-harvest fish losses, and improvement in incomes of fishers and fish traders. Implementation of the up-scaled phase in Kenya should continue, incorporating additional information, especially export data.

FAO should study the model of the project in Kenya with a view to supporting expansion of the system to other countries in Africa and adapting the model for other small-scale fisheries. Alain Le Bail Institut international du froid , M. Mme Yvette Diei- Ouadi, M. Jogeir Toppe et M. Anass Karzazi communication et correspondant ; et M. Secretary of the Indian Ocean Tuna Commission am: Value chain approach and clam farming in the Gulf of Gabes.

However, it has not been practiced in Uganda despite its commendable success elsewhere in the world. Probably this lack of practice has contributed to the slow pace of farmed catfish Clarias gariepinus commercialization in Uganda. As a result some farmers have benefited less from their aquaculture enterprises due to low consumer acceptance and limited local market access because of the dark appearance of processed products. Despite the preservative effect of smoke, catfish ostensibly has a limited shelf life, which has undermined its availability as a source of animal protein in certain parts of the country.

Considering the declining per capita fish consumption in Uganda and the need to popularize aquaculture-based fishery products, it was deemed necessary to undertake the present study. About 60 farmed catfish were divided into four equal batches. The results indicated that fish that was bled had a longer shelf life than fish that was not bled, regardless of the holding temperature.

Under chilled conditions the shelf life of bled fish was extended by 11 days while fish kept under ambient temperatures remained acceptable for an extra 5 hours compared to fish that were not bled. It was therefore concluded that bleeding and chilling intervention measures improved and extended shelf life of catfish. Application of these strategies in aquaculture systems would undoubtedly enhance local as well as international catfish trade for whole or processed products, improved food security and the fight against malnutrition in Uganda by increasing consumer acceptance.

In fisheries, struggling fish are sometimes stunned by a blow on the head or by electric shock Trestven and Patten, or immersed in chilled water to facilitate the killing procedure. Adequate research has not been done to show the effect of bleeding and stunning on fish flesh quality although the literature indicates advantages from these practices.

The removal of blood by making cuts or by evisceration has been noted as a means of accelerating death Howgate, and retarding spoilage Fellows, and preserving the quality Braker, The incision may be made at the caudal peduncle or nape depending on fish species. A cut at the isthmus severs the ventral aorta; at the nape, it severs the dorsal aorta and the spinal cord as well, thereby immobilizing the fish; and at the caudal peduncle, it excises the tail and severs the dorsal aorta. In Salmo gairdneri, the greatest amount of bleeding occurred with the caudal peduncle cut Trestven and Patten, Catfish Clarias gariepinus , is the leading farmed fish in Uganda FAO, , , followed by tilapia and mirror carp in order of commercial importance.

Owing to the fish farming pattern in Uganda, catfish is usually marketed live or in processed particularly smoked form. The recent Department of Fisheries Resources DFR report indicates that there were 20, fish farmers with an average pond size of m2 per farmer and mean production yield of 1. Besides, catfish grows faster than tilapia species Haylor, As such, many entrepreneurial farmers have massively invested in aquaculture to take advantage of the high production yield and the market niche provided by the African diaspora in Europe.

According to Onega et al. Despite the absence of standards for catfish, Uganda is one of the five countries allowed to export products from farmed fish to the European Union EU. Indeed according to DFR significant quantities of smoked products have been exported to Europe since to cater for the African ethnic minorities. Quality is a subjective parameter which varies with type of product and end-user.

In the fisheries sector, it may be defined as the degree of excellence or spoilage undergone by fish Afolabi, ; Huss, It is influenced by a number of major factors that include; high temperatures, handling practices and initial microbial load. In aquaculture systems and particularly in catfish, additional influential quality factors include fish feed, bleeding and stress.

Bleeding soon after capture or harvest contributes substantially to consumer acceptance, based on appearance colour. Although the national production of catfish was estimated at 33, tonnes, local consumption is fairly low due to its red discolouration of fillets and varying geographical preferences within the country. The unappealing discolouration of the flesh has been attributed to post-mortem retention of blood. The retained blood provides sufficient nutrition for the evading post-mortem spoilage bacteria Frenly, which may ultimately shorten the keeping quality of catfish Howgate, ; Huss, According to Martin , the iron component in the haemoglobin molecule catalyses oxidation and formation of yellow spots in salted fish.

Although significant quantities of smoked catfish are exported as well as locally traded, they have limited shelf life, despite the preservative effect of smoke Masette, Consequently, the limited shelf life compromises the marketing time for both processed and unprocessed catfish which in turn affects its availability as an important source of animal protein to reduce malnutrition James, in certain parts of the country.

The current status quo negatively impacts on the financial benefits of some farmers and traders of processed fish and as a result undermines the campaign to promote aquaculture enterprises in Uganda. On the contrary, if the blood was removed by bleeding the resultant product would be acceptable to majority of consumers and it would invigorate the campaign.

According to Outdoor bled fish results in a white, acceptable fillet and extends shelf life, which is attributed to the reduced quantities of haemoglobin that reduces susceptibility to oxidative rancidity Martin, It has been observed that fish blood remains in fluid form for about 30 minutes after capture Howgate, and therefore it can easily be removed by the jerking action of a dying fish. In some marine fish species, bleeding is a recommended procedure for colour enhancement and shelf life extension Ahimbisibwe et al. Bleeding of fish is required in some tuna-like species to preserve fish quality Braker, Despite the benefits of bleeding, this significant step is hardly practiced in Uganda, probably due to lack of knowledge or appropriate facilities The generation of data on the effect of bleeding on keeping quality of catfish will contribute substantially to the international export trade and will also enhance marketability, and acceptability of catfish fillets among local consumers.

If technical information to backstop the Uganda National Bureau of Standards UNBS in the formulation of local standards is not undertaken as a matter of urgency, it will jeopardize putting Ugandan catfish on the international market in the near future. Besides, the per capita fish consumption, which had declined from 13 kg in to the present 6 kg would be substantially increased by consumption of catfish. Overall objective of the study To assess the effect of bleeding on the keeping quality of catfish held at designated temperatures. Specific objectives a To determine iron content in bled and unbled catfish at ambient and chilled temperatures.

A total of 23 fish samples were bled and a similar number was left unbled. From the unbled batch 13 were similarly kept in another ice box and the remaining 10 were left at ambient temperature. Bleeding Each catfish was firmly held down on a chopping board then, with a sharp pointed knife, an incision was made behind the operculum to cut through the artery to allow blood to flow out. Blood flow was accelerated by hanging the fish upside down and the jerking action of the fish. After 30 minutes, the blood stopped dripping and the fish was gutted prior to storage either on ice or in ambient conditions depending on treatment.

The unbled batch of catfish were humanely killed by immersion in chilled water for 30 minutes and then also gutted prior to treatment.

Transportation of samples After all preliminary treatments at the farm, all samples were transported to the Makerere Department of Zoology laboratory for subsequent tests. Sampling plan One piece of fish from each batch of samples kept at room temperature was sampled every two hours and subjected to sensory assessment by a panel of 12 trained individuals. While one fish from each batch held at chilled temperatures was sampled once after 7 and then 14 days.

Subsequently, after the 14th day, sampling was every other day. Sensory assessment The two fish sampled 1 bled and 1 unbled were held at ambient temperature and sampled every two hours. They were cut into 12 steaks weighing approximately 5g each, incised from the middle part of the fish and steamed in a closed beaker for 10 minutes before serving to a taste panel of trained individuals. Each panelist was requested to score the general acceptability of the sample on a hedonic scale of 1—5.

Determination of iron content About 0. The ash was dissolved in aqua regia at 3: The solution was aspirated by atomic absorption spectrometer AAS to quantify the iron content.

Essentially, the procedure removes significant amounts of blood that would have provided sufficient nutrition for the invading post-mortem spoilage bacteria Frenly, Besides, the iron from the haemoglobin molecule in the blood is one of the precursor ionic free radicals that normally catalyze lipid oxidation in fish Huss, and therefore its removal in significant quantities should prolong the onset of oxidative rancidity.

In catfish, the bleeding procedure reduced the iron content by a factor of 1 in fish held at ambient temperatures and by almost 1. The difference may be attributed to the rinsing effect of melting ice which ultimately contributed to bleaching of the flesh. However, there was no significant difference attributed to holding conditions. Implying that temperature does not affect the levels of iron content Martin, Table 1. However, in the present study the focus was on sensory evaluation due to limited funding to purchase chemicals for chemical and microbiological methods.

In the study, point of rejection at mean score 2 was 14 hours and Ice may not be easily available in the vicinity of remote fish farms and even if it was available, the cost may be prohibitive for the majority of fish farmers. The difference of 5. Consistent transaction of high quality bled catfish at least-cost holding temperatures would be another avenue of promoting aquaculture in Uganda. On the contrary, catfish held at chill conditions in ice was rejected at score 2 on the 17th day for unbled and the 29th day for bled when both batches of catfish were chilled Figure 2. The difference of approximately 12 days offers ample time for sales on local as well as international markets without incurring losses attributed to quality deterioration.

Implying that bleeding together with chilling as compared to chilling alone has a significant effect on the shelf life of catfish. According to Martin , removal of blood delays collagen fibril degradation and muscle softening of pelagic fish Ando et al. Several authors ascribe the extended shelf life to reduction of nutrients for the invading spoilage bacteria Frenly, ; Venugopal, while Huss highlights the reduction of the iron content.

In iced fish samples, shelf life may also be extended by the washing effect of ice Chen and Chai, Since the three factors appeared to happen concurrently, it is plausible to suggest that synergistic tendencies between the three factors have a combined effect as observed in both batches of catfish that were bled but kept at different temperatures.

However, the synergistic effect of blood removal; reduction of nutrients for invading spoilage microbes and reduction of haemoglobin iron, coupled with the effect of chilling increases the keeping quality of catfish by almost two weeks compared to similar batches that were not bled and kept at room temperature. Effort should also be made to incorporate the effect of feed regimes practiced by different x farmers on the quality of farmed fish products; x Farmed catfish should be bled to enhance its local marketability; Bleeding procedures should be inserted in the Quality Assurance rules of which have been x incorporated in the Fish Act as a mandatory practice for farmed catfish; and The qualities of bled catfish should be used as a strategy to promote fish farming in Uganda.

Quality change of traditionally processed fresh water fish species. Nutritive and organoleptic changes. Journal of Food Technology, 19 3: Effect of bleeding on the quality of amberjack Seriola dumerili and red sea bream Pagrus major muscle tissues during iced storage. Post-mortem softening of fish muscle during chilled storage as affected by bleeding. Journal of Food Science, 64 3: Extension Sea Grant Program. Micro flora of drainage from ice in fishing holds. Applied Environmental Microbiology, Advances in fish science and technology.

The state of world fisheries and aquaculture, Publication related to aquaculture of Uganda, Rome. Fishery and Aquaculture Statistics. Principles of food preservation http: Explaining the techniques of bleeding fish. Review of the public heath safety of products from aquaculture. Article first published online: Quality changes in fresh fish. The prospects of fish for the undernourished. FAO Food and Nutrition, Rich Fisheries, Poor fish folk, Socio-economics of L.

Liquid smoke treatment as an alternative method to traditional smoking in fish processing. University of Lincoln UK. Fisheries Development and aquaculture. East African Business Week. Meeting the increasing demand for fish in the Lake Victoria Basin through development of aquaculture. Marine Fisheries Review, 43 4. Extra cellular proteases of contaminant bacteria in fish spoilage: Cardinal Abstract The challenge of preserving seafood after capture is most of the time associated with refrigeration and the cold chain.

Depending on the place of capture, different technologies can be used. This paper presents an overview of selected technologies, mostly used on land. Freezing addresses different issues, particularly in terms of energy demand; consideration of the recommendations of the international institute of refrigeration, can result in substantial energy savings.

Focus is then placed on recently developed technologies: Superchilling consists of preserving products at temperatures close to the initial freezing temperature; such a strategy permits reduction of water activity and potentially leads to extension of shelf life gelation. High pressure processing can be used to freeze products and also to process seafood.

High quality frozen foods can be obtained with pressure shift freezing process with refined ice crystallization. More recently, freezing under an electric field has been developed and applied to seafood; recent results demonstrate the advantages of electro-freezing in terms of microstructure. Other examples regarding food preservation are quoted in Table 1. The IIR is an Intergovernmental organization with more than 60 member countries representing over 60 percent of the total world population.

The International Institute of Refrigeration IIR is the only independent intergovernmental organization which promotes knowledge of refrigeration and associated technologies that are necessary for life in a science-based, cost-effective and environmentally sustainable manner including: The journal of the IIR is the International Journal of Refrigeration Elsevier , which is ranked 19th out of Journals in mechanical engineering and 13th out of 49 Journals in thermodynamics.

The IIR website provides a unique data base gathering all the technical data needed and also many facilities such as Newsletters. Organisation of the 10 technical Figure 3. Freezing is one of the preferred methods, especially for long-term preservation. In particular when seafood is used by the food manufacturing industry, frozen products offer convenience even though freezing may lead to substantial changes in the organoleptic quality. Figure 3 presents an overview of different seafood sources and the different technologies that can be used for preserving them. Apart from salting and drying, and also in some cases smoking, refrigeration is often required to extend the shelf life of seafood.

In this article, we provide an insight into selected technologies associated with refrigeration. There are different issues related to freezing, in particular its energy demand. Based on the consideration of the IIR, a recommendation can be proposed resulting in substantial energy savings. Such examples of recently developed technologies that may result in energy saving are superchilling, high pressure processing and freezing under a static electric field.

Superchilling consists of preserving products at temperatures close to the initial freezing temperature; such a strategy permits reduction of water activity and potentially leads to extension of product shelf life. High pressure processing can be used to freeze products and also to process seafood for better quality products. High quality frozen foods can be obtained with the pressure shift freezing process with refined ice crystallization.

More recently, freezing under an electric field has been developed and applied to seafood; recent results demonstrate the potential advantages of this technique terms of microstructure and reduction in drip loss. Therefore, there is a stake in optimizing the energy demand for the refrigeration process applied to any food.

The freezing process usually starts with a non-frozen product at chill temperature. Freezing is sometimes done cryogenically, which permits very high freezing rates. However, the availability of cryogenic fluids liquid nitrogen, solid carbon dioxide on production sites is not always possible and cryogenic freezing is restricted to selected cases.

Compression units are mainly used for the freezing of seafood. Freezing can be carried out with unwrapped products using air or brine as a refrigeration media. In some cases, such as onboard freezing, seafood is usually frozen using plate freezers. The fish mostly filleted are placed in plastic pouches that are put in a carton.

The carton is closed when full and is frozen directly. Even though a lower temperature yields a reduction of the COP, in some cases, it allows global energy savings due to a reduced freezing time see for example Le Bail et al. The final temperature of the product at the end of the freezing process has also a big impact on the global energy demand.

Indeed, the set point temperature of the ambient temperature during freezing is always much lower than the set point temperature in frozen storage. Therefore, the freezing equipment has a lower COP in comparison to the frozen storage. According to the criterion proposed by the IIR, a product can be considered as frozen if, either: Frozen food can then be transferred to frozen storage.

This way of managing the final freezing temperature may result in substantial energy savings without altering the final quality of the frozen products. Indeed, most of the ice crystallization takes place between the initial freezing temperature and a few degrees Celsius below this temperature. Freezing and the completion of the water to ice transition can be achieved in frozen storage with a lower energy demand than for freezing equipment.

An overview of the superchilling process was proposed recently by Kaale et al. The objective of superchilling is an extension of the shelf life because of the lowering effect on water activity of the products. Accordingly, a reduction of the growth rate of microorganisms is expected, due to a synergistic effect of the reduction of water activity and temperature. Superchilling can be considered as an intermediate process in between chilling and freezing.

The implementation of superchilling technology is on the rise. In particular it has been adopted by several smoked salmon producers. Figure 4 shows the depression of water activity of ice as a function of temperature. Considering a frozen product, the laws of thermodynamics control the equilibrium between each phase. In particular, in the case of freezing, the partial vapour pressure of the aqueous solution present in the product must be equal to the water activity of ice. In the case where freezing is expected to lead to substantial damage to the flesh of seafood products, superchilling is expected to result in improved quality.

There is still a controversy between authors regarding the real benefits and drawbacks of superchilling. For example Beaufort et al. After 28 days of storage, a positive effect on the development of Listeria monocytogenes was observed lower growth than control. Regarding the sensory evaluation, all sensory parameters were not affected.

They concluded that further studies related to superchilling are needed to better understand the changes observed in the period ranging between day 14 and day They concluded that superchilling allows a doubling in shelf life chemical, microbiological and sensory. These authors also concluded that there is a large need for help with implementation of superchilling in the industrial process.

The major challenge of superchilling lies in the precise control of the temperature; indeed, slight departure from the set point may result in HACCP risks Hazard Analysis Critical Control Points. Since temperature control is very difficult and often inadequate, a new principle based on the control of the ice fraction in the food would be necessary. Moreover superchilling requires the establishment of a new channel among the existing conventional channels of the cold chain. However, at the scale of a company storing its own production, superchilling can be relatively easily set in operation to extend the shelf life of products.

This is critical for example in the smoked salmon industry, which faces peak demands during certain periods of the year Christmas, Easter, etc. Bridgman, , for example showed that a pressure of MPa was able to coagulate albumin, and also studied phase changes under pressure.

After closing the vessel, a pressure intensifier is used to increase the pressure up to the required level. Due to the compressibility of water: The order of magnitude of these changes is an increase in temperature of 4K for an increase in pressure of MPa. There are basically three main areas of application of HPP to food systems: Some technological barriers limit the pressure level.

Nowadays, industrial applications are currently working at pressures of MPa, whereas scientists and researchers might investigate up to MPa. Higher pressures can be obtained several orders of magnitude of kilobars with special systems but with miniature volumes. HPP of seafood has been investigated by several authors. Among the most promising applications already implemented in the industry is the shucking of oysters by some companies in Australia and in USA. This process permits the extension of shelf life of oysters in refrigerated conditions after HPP.

The shell is usually circled with an elastic ring. This process permits the opening of large oysters very easily under pressure and also inactivates specific microorganisms Vibrio. Another interesting application has been developed in Canada to process lobsters. Using this process the lobster meat can be removed very easily in one piece.

Other fields of application have been developed for meats, ready to eat meals, rice, fruits, sauces, etc. Regarding freezing, high pressure technology permits very high freezing rates, due to the pressure shift freezing process. The phase change temperature of water is depressed with increasing pressure until MPa. Above this pressure, the opposite phenomenon is observed see Figure 5. The pressure shift freezing process is based on the very specific property of the depression of the freezing point. The food is first pressurized in a high pressure vessel at negative temperature.

Then the pressure is released as shown in Figure 6. Phase diagram of water under Figure 6. Scheme of the pressure shift freezing pressure. However, the HP at MPa exposes the proteins contained in the food to partial denaturation, resulting in increased toughness similar to semi cooked products.

Even though there is evidence showing a reduction of ice crystals size see Figure 7 and Figure 8 — from Alizadeh et al. Indeed, the conventional freezing techniques are relatively satisfactory and the benefit brought by HPP is not sufficient to overcome the cost of the equipment. Only in the case of few products such as oysters and lobsters has HPP been effectively implemented by the industry. HPP raises some regulatory issues as not all countries necessarily accept this technology. In particular in Europe, there are regulatory constraints which limit the use of the technology, whereas in the USA, HPP has been accepted for selected products.

Blast air frozen salmon fish. Pressure shift frozen salmon fish. Several authors have related the presence of currents during formation of crystals. The voltage is explained by the embedding of ions in the semi crystalline structure, resulting in a diffusion of electrical charges and consequently in the presence of a current and of a potential difference. The application of an external electrostatic field is thus likely to affect the phase change phenomena. This has been demonstrated theoretically. For example Goldman et al. Due to the re-orientation of water molecules, hydrogen bonds are stronger along the field than along orthogonal directions Wei et al.

Some authors reported that with increasing field strength, a water system has a more perfect structure that is similar to an ice-like structure. The possibility of obtaining liquid water with more structural regularity by applying an electric field was also suggested by Jung et al. The application of electric disturbance during freezing in aqueous systems may thus be of interest in terms of control of the crystallization phenomenon. This has been investigated by some authors. In the case of aqueous systems, several references are available as well. However, most existing experimental work is based on the application of a moderate current flowing through an aqueous solution during freezing.

In a recent study Wei et al. The design of the equipment is based on the patent of Owada et al. Recent studies done in our laboratory with selected fish products frozen in this equipment showed that a slight reduction of the size of the ice crystals was effectively obtained. Histological sections of cod fish fixed by a Carnoy solution in a frozen state — see Alizadeh et al. The industrial application of this technology is on the increase, especially for high value products that demand a high freezing quality.

It is likely that similar advantages in terms of microstructure can be achieved using cryogenic freezing. The economic and technological comparison has to be done to conclude on this specific technique. This technology also introduced concerns on some safety issues, such as high voltages several kV which are in operation in a humid environment. However, high voltage may lead to some degree of microbial inactivation thanks to the presence of ozone under selected operating conditions.

Cod fish frozen in a blast air freezer. Cod fish frozen under electric field. White spots are ghosts of ice crystals. Unpublished White spots are ghosts of ice crystals. Le-Bail in collaboration with Grimsby from Prof. Chilling is extensively used for short term preservation. However, long term preservation is needed to meet the expectations of the industry and of consumers. Freezing addresses different issues in terms of quality, of cost and also of environmental impact. Even though freezing has a larger environmental impact than chilling technology, it is the only technology that can limit the food loss to a minimum.

Several refrigeration innovations are still being developed to overcome the damage caused by freezing. Among the most promising technologies are high pressure, superchilling and freezing under high electric field, which are expected to provide new cost saving avenues and quality retention in sea foods to the industry and to the global seafood market. However, it is likely that these technologies will remain as niche applications for some time, and that freezing using conventional compression units will remain in the long term the most preferred freezing technology, mainly for the economic reasons.

Effect of different freezing processes on the microstructure of Atlantic salmon Salmo salar fillets. Innovative Food Science and Emerging Technologies, 8: International Journal of Refrigeration. Water in the liquid and five solid forms under pressure. Proceedings of the American Academy of Arts and Sciences, Pressure-assisted freezing and thawing: Food Review International, 16 4: Surface structure of water and ice.

Liquid water and freezing, in The chemical physics of ice. Philosophical Transactions of the Royal Society A, Superchilling - innovative processing of fresh foods. The effect of an external electric field on the structure of liquid water using molecular dynamics simulations. Chemical Physics, 2—3: Journal of Food Engineering, 2: High pressure freezing and thawing of foods; a review. International Journal of Refrigeration, Evaluation of the mean ice ration as a function of temperature in an heterogenous food; application to the determination of the target temperature at the end of freezing.

Energy demand for selected bread making processes: Conventional versus Part Baked frozen technologies. Journal of Food Engineering, Isothermal crystallization of poly vinylidene fluoride in the presence of high static electric fields. Effect of crystallization temperature and electric field strength on the crystal phase content and morphology Journal of polymer science: On the electrical effects that accompany the spontaneous growth of ice in supercooled aqueous solutions.

Journal of Geophysic Research, Effects of dipole polarization of water molecules on ice formation under an electrostatic field. The Indian mackerel, Rastrelliger kanagurta is a popular fish in Seychelles, much liked by the consumers when still in the fresh state. An excess of this species is harvested during the good season from November to April.

During this period, the local market quickly becomes saturated and a lot of the fish goes very cheaply for use as fishing bait. At times the fishers would also avoid harvesting due to lack of an outlet for the catch. The Gambian continental shelf ecosystem in and Heymans and Jan Michael Vakily Palomares and Daniel Pauly However, the main reason for the much depleted state of West African fisheries resources lies in the presence, along the West African coast, of a huge array of Distant Water fleets from Western and Eastern Europe, and from East Asia.

Evaluations of the effects of the resulting fishing effort on West African resources have been rare so far, and widely scattered, as they were mainly dealing with isolated, local stocks. Broad-based studies, on the other hand, have been entirely lacking. This report begins to fill this gap in that it covers much of the West African coast. However, the focus has been on one region Northwest Africa , for which a synthesis, i.

This report focuses on descriptions of the methods and data used in this synthesis, i. These models were subsequently refined in extensive collaboration among the editors and the authors, which culminated in a third workshop jointly organized by the Sea Around Us and SIAP projects, held in January at the Fisheries Centre, University of British Columbia, Vancouver, and attended by three members of the SIAP project, representing Mauritania1, Senegal and The Gambia. The food web models resulting from this process were complemented by models initiated by members of the Sea Around Us project, for Sierra Leone, Guinea and the Central Atlantic.

This first-ever coverage of the entire Northwest African subregion with ecosystem models, mostly pairs covering two different periods in the same country, allowed the creation of regional biomass maps for and , illustrating the massive decline of the abundance of larger fishes along the West African coast.

This, we assume, should impact on negotiations about access by Distant Water fleets. Michael Vakily, Coordinator of the SIAP project, must also be thanked for his untiring support of the work summarized in these pages. Daniel Pauly December 1 The printed version of this report failed to include a paper describing the Mauritanian ecosystem in and , included in this online version.

Ecosystem based fisheries management: In the late 19th Century, in the North Sea, where British steam trawlers were first deployed, it took only a few years for the accumulated coastal stocks of flatfish and other demersal groups to be depleted, and for the trawlers to be forced to move on to the Central North Sea, then further, all the way to Iceland. By the late s, the last large shelf areas previously not subjected to trawling had been depleted, as were most of the oceanic seamounts.

All that is left now for further expansion of bottom trawling are very deep km populations of demersal fish, whose extremely low growth rates, associated with life spans of over years, essentially precludes sustainable exploitation. Similarly worrying trends are occurring in open water ecosystems, where long-lining for tuna and other large pelagic fishes depletes these systems of large predators including sharks, now feeding an insatiable Asian soup fin market. Also, purse seining around floating objects i. The change in demersal and pelagic ecosystem structure resulting from such serial depletions can be quantified in various ways, one of them being through the decline of the trophic level in the landings of fisheries.

This establishes that catches in most parts of the world, including North West Africa, are not sustainable, as they increasingly rely on fish originating from the bottom of marine food webs, i. Moreover, ecosystem-based management will require routine use of marine 2 Cite as: West African marine ecosystems: Fisheries Centre Research Reports 12 7. West African marine ecosystems, M. Pauly 3protected areas with no-take zones at their core to allow rebuilding and maintenance of now depleted populations of slow-growing fishes.

For such management to be put in place, a convincing case must be made that the bleak picture of global fisheries presented applies to the region for which a change in management regime is being proposed. For this purpose, SIAP was designed, via its three main modules, to access three key types of data: Jointly, the results of the analyses to be conducted in these three modules will provide, for each country, a reliable synthesis of the long-term impacts of fishing on the marine ecosystems of the region, and hence of the option still available for their sustained exploitation.

Thus, the SIAP project will help choose between two futures: The other would lead to a form of fisheries management involving strong action being taken to maintain the ecosystems upon which the fisheries are based. This would include ecosystem-based criteria for the operation of local fisheries, and the licensing of foreign ones, and a strong reliance on spatial closures including relative no-take area as a tool for resource conservation. The SIAP project has organized, with a number of partners, an international symposium, held in Dakar, in June , at which these options and their biological, economic and societal implications were debated.

We hope that the SIAP project as a whole will be as successful as this symposium was. An Ecopath model is used to determine the impact of the recent development of elasmobranch and demersal fisheries in the region. This model provides a multispecies management strategy taking into consideration the trophic activities of all the predators present in the system humans, birds and apex predators.

This model seems to be robust even if the estimated values of some of the initial parameters appear uncertain. Echassiers et flamands roses. Il consomme essentiellement du macrobenthos Wolff et al. Le poids moyen de chaque individu de ce groupe est de g. La tortue verte, Cheliona mydas, est ubiquiste. De bonnes observations sont aussi possibles depuis le cap Tafarit. Sevrin-Reyssac et Kuipers et al. Pour la seconde zone on obtient: En appliquant le facteur de conversion du C en poids humide on obtient: De Jong et al.

Pauly 9 Tableau 1. D iop 10 Tableau 2. Arvy, C and Dia, A. Environnement et littoral mauritanien. Actes de colloques juin Evaluation de la ressource halieutique Evaluation directe. Rapport final janvier-juin version provisoire. Delta Institute for Hydrobiological Research, Yerseke. The trawl fauna of the Mauritanian shelf Northwest Africa: Van Der Land, P.

Ecological studies in the coastal waters of Mauritania: Proceedings of a symposium held at Leiden, The Netherlands, March Concepts, design and data sources. Inventaires ichtyologiques des eaux mauritaniennes. A trophic model of a Mediterranean lagoon, Etang de Thau, France, p. Trophic models of aquatic ecosystems.

Diet composition and trophic levels of marine mammals. A model of trophic flows in the northern Benguela upwelling system during the s. Mass-Balance Models of North-eastern Pacific ecosystems. Fisheries Centre Reports Vol. Rate of metabolism and food requirements of fishes. The models are structured in 38 groups, of which 25 are fish. The comparison of the two periods showed the generalised decrease in biomass of demersal species and, as a consequence, of the decrease of the average trophic level of the catches between and The next step will be to verify that the model is able to reproduce the observed time series of biomass and catch.

Elle permet sans doute un meilleur couplage des productions primaires et secondaires au-dessus du plateau Binet, La ZEE mauritanienne, M. La biomasse annuelle est la moyenne des campagnes de chalutage de la saison froide et de la saison chaude. Ajustements aux biomasses Les estimations de biomasses avaiplateau. La biomasse de serait donc la somme de la biomasse du plateau et de celle des strates plus profondes. Le poids individuel provient de Trites et Pauly Pauly 17 Tableau 1. Pauly 19 Tableau 2. Pauly 21 Tableau 3.

Pauly 23naevus Ellis et al. Ce groupe ne fait pas l'objet d'exploitation en Mauritanie. Les biomasses sont de 0. Les captures atteignent 0. Les biomasses pour et sont respectivement de 0. Pauly 27microlepis ; la sole-ruardon commune, Synaptura lusitanica nigromaculata ; et la sole velue, Monochirus hispidus.

Mugil cephalus et M. Fridtjof Nansen, atteignant seulement 0. Trichirus lepturus et Lepidopus caudatus. Il s'agit du roi des harengs, Regalecus glesne et du cordonnier bossu, Alectis alexandrinus. Nous ne disposons pas de biomasse ou de capture pour ce groupe. On y place aussi Caranx hippos , Caranx senegallus, Trachurus picturatus, Trachurus mediterraneus et Decapterus punctatus. Le chinchard jaune est aussi tropical. Utilisant une valeur de 0. Diop estime la biomasse totale de praires entre 1 million et 2.

Une biomasse moyenne de 0. Macrozooplancton Ce groupe comprend essentiellement les hydrozoaires et les scyphozoaires. En fixant un poids moyen de 50 mg par larve, on obtient une biomasse de 1. La biomasse totale pour ce groupe est donc de Pauly 33 Tableau 6. Journal of Marine Biology Association U. Memorandum on the mass die-off of monk seals on the Cap Blanc peninsula.

Nouadhibou Septembre, , 65 pp. Albacore detailed report. Bigeye tuna Thunnus obesus , Executive summary. Mass-balance models of North-eastern Pacific ecosystems. Comparative studies of coastal pelagic fish reproductive habitats: Journal du Conseil International pour l'Exploration de la Mer, Aquatic Living Resources, 1: Diets of lagoon fishes of the Solomon Islands: Predators of tuna baitfish and trophic effects of baitfishing on the subsistence fishery. Population dynamics in benthic invertebrate, a virtual handbook.

Seabirds of the senegal upwelling and adjacent waters. Movements, feeding periods, and daily ration of piscivorous young-of-the-year bluefish, Pomatomus saltatrix, in the Hudson River estuary. Advances in assessment of world cephalopod resources. Observations des oiseaux marins au large de la Mauritanie. Feeding habits of Alepocephalus rostratus Pisces: Alepocephalidae in the Western Mediterranean Sea. Whales, dolphins and porpoises. The visual guide to all the cetaceans. Stoddart Publishing, Toronto, Canada. Les ressources halieutiques de la ZEE mauritanienne.

A comparative study of the diet of Loligo vulgaris Lamarck, Mollusca: Standardized diet compositions and trophic levels of sharks. Oxford University Press, Oxford. Ostrich to Ducks, pp. Acta Adriatica, 42 1: Les peuplements de poissons des milieux estuariens de l'Afrique de l'Ouest: L'exemple de l'estuaire hyperhalin du Sine-Saloum. On the feeding of Alfonsino Beryx splendens.

Journal of Ichthyology, 29 5: The trawl fauna of the mauritanian shelf Northwest Africa: The comparative feeding ecology of six species of shark and four species of ray Elasmobranchii in the north-east Atlantic. Espectro alimentario del patudo Thunnus obesus en la primavera austral de en el Pacifico sur oriental. Feeding relationships of a demersal fish assemblage on the west coast of Scotland. Journal of Fish Biology, Studies of an Upwelling System.

A review of the world resources of mesopelagic fish. Cephalopoda of the Azores. Life and and Marine Sciences. Octopus vulgaris Cuvier polvo-comum: Journal of Ichthyology, 30 7: The Azores Archipelago, Fisheries impacts on North Atlantic Ecosystems: Food partitioning among scorpaenid fishes in Mediterranean seagrass beds. Comparative modelling of trophic flows in four large ecosystems: Global versus local effects.

Global versus local changes in upwelling systems, pp. Seasonal changes in the Peruvian upwelling ecosystem. Trophic models of aquatic ecosystems, pp. On currents off north-west Africa as revealed by fish larvae distributions.

Radio Zoran Italy 1

Zooplancton distribution in the coastal upwelling system along the Banc d'Arguin, Mauritania. The foraging ecology of two pairs of congeneric demersal fish species: Seabirds in the shelf edge waters bordering the Banc d'Arguin, Mauritania. Benthic-pelagic coupling and export of organic carbon from a tropical Atlantic continental shelf - Sierra Leone. Estuarine, Coastal and Shelf Science, Etat des observations en Predation patterns of demersal teleosts from the Cape south and west coasts of South Africa.

Benthic and epibenthic predators. South African Journal of Marine Sciences, A Trophic Ecosystem model of Lake Georges. Trophic Models of Aquatic Ecosystems Ed. The food of Sardinella aurita Val. Parc National du Banc d'Arguin, Bul. Trophic interactions in Caribbean coral reefs. Ortiz de Zarate, V. Collective volume of scientific papers. Ould Taleb Ould Sidi, M. A multiple regression model for predicting the food consumption of marine fish populations. Australian Journal of Marine and Freshwater Research, On the interrelationships between natural mortality, growth parameters, and mean environmental temperature in fish stocks.

Primary production required to sustain global fisheries. Fishing down the food web. Improved construction, parametrization and interpretation of steady-state ecosystem models. Bluefin tuna food habits. Iverson, Fisheries Bulletin, Food habits of reef fishes of the West Indies. Partitioning of space and food resources by three fish genus Diplodus Sparidae in a Mediterranean rocky infralittoral ecosystem. Marine Ecology Progress Series, South African Journal of Marine Science, A preliminary model of the Atlantic coast of Morocco for the mids.

Food, feeding habits, and estimates of daily ration of the shortfin mako Isurus oxyrinchus in the Northwest Atlantic. Canadian Journal of Fisheries and Aquatic Sciences, Estimating mean body masses of marine mammals from maximum body lengths. Canadian Journal of Zoology, Competition between fisheries and marine mammals for prey and primary production in the Pacific Ocean.

Journal of Northwest Atlantic Fishery Science, Marine mammals and birds. The food of the grey mullet Mugil cephalus L. An Ecopath model of the continental shelf system for the period to , coinciding with the establishment of a statistical collection system and the undertaking of the first systematic surveys, was built to provide estimates of fisheries catches and biomass for different fish stocks. This model takes into account the migration of important fish species such as tuna.

The structure of the model is discussed and mixed trophic impact analysis was undertaken to determine the direct and indirect effects of biomass changes within and between groups in the system, including the effects of fishing. One result that stands out is the relatively modest effects of fishing on the system in the period to Fishing with artisanal handlines, the dominant gear type, had negative effects on target species such as pelagic and demersal predators, but fishing pressure for other groups was negligible.

The biomass estimates of the model, as well as the biomass estimates based on survey results, indicate that previous assessments of potential harvest, which ranged from 25 to 58 t, may have been too optimistic, particularly for demersal species. Ecopath model of the Cape Verde coastal ecosystem, p. The Cape Verde coastal ecosystem, K. Sto bberup et al. Unsustainable fishing practices coupled with an excessive level of investment in fishing capacity have resulted in serious degradation and low yields in the stocks of developed countries, creating new pressures on the resources of developing countries.

These pressures are largely trans-national, highlighting the importance of regional aspects to resource management e. Efforts to improve the current state of affairs in fisheries include the introduction of the ecosystem approach to assess the direct and indirect effects of fishing e. One possible tool for such an approach is Ecopath with Ecosim, which was developed using the mass-balance approach Christensen and Pauly ; Polovina Ecopath models are relatively straightforward to construct and require limited information as opposed to more data-driven approaches such as MSVPA, making it more feasible to apply in tropical scenarios such as in Cape Verde.

Furthermore in connection with Ecopath, a rich theoretical framework exists for the analysis of energy flows or cycling in ecosystems and it is straightforward to compare these flows between different time periods in the same system, or among similarly structured systems Anon. Ecopath was initially a deterministic steady-state approach model and it has been further developed since, making it possible to i address uncertainty around impact variables for balancing the model and deriving system-level metrics; and ii to simulate changes in fishing pattern and intensity through time and space in an ecosystem framework Christensen et al.

The islands are of volcanic origin, rising from a depth of at least 3 m, and the continental shelves, generally narrow and irregular, are limited to a total area of 5 km2 Bravo de Laguna The eastern islands Sal, Boavista, and Maio, form one system with a more extensive continental shelf compared to the other islands. Although the continental shelf area is of limited area, the EEZ of Cape Verde covers an area of about km2, much of which is not exploited by the national fisheries Figure 1.

Map of the Cape Verde Archipelago indicating the relatively limited shelf area. Bathymetric lines indicate depths of m, 1 m, and 3 m, respectively, which is best seen around the Boavista-Maio continental shelf. There is a natural division between the north-western and eastern islands, which are separated by depths of approximately 3 m. The climate of Cape Verde is characterized by warm, relatively even temperatures, ranging from an Hanek et al. Winds are predominantly north-easterly, except for the period from December to March, the colder, dry season, where the winds are predominantly easterly West African marine ecosystems, M.

Pauly 41The archipelago is situated in the southern part of the12, Canary Current System. During the period from July to November, changes occur in the intensity and position of the St. Helena and Azores anticyclones, resulting in a predominantly southwestern current along the southern islands, thus causing warmer waters to reach these southern islands. However, the total number of species caught and their other tropical areas.

Estimated total catch in Cape Verde as well as catches by the artisanal Art and industrial Ind fisheries in Cape Verde INDP , including a revision of statistics for the period to see text for an explanation of the revision process. Estimated Catches t g r. Due to the rising number of fishing vessels, there is a trend of lower catches per effort Carvalho ; Medina and Tavares and lower biomass estimates for demersal fish stocks, in particular Marques Some selected surveys undertaken in the Cape Verde Archipelago, including the general objectives and the main source of information.

In relation to fisheries, many studies and characterisations have been undertaken, including single species es and intensity. Early surveys undertaken in Cape Verde tended to be exploratory and qualitative in character Reiner ; Vieira , whereas gstock assessments on economically important species such as lobsters and scad mackerel Decapterus macarellus e. Almada ; Carvalho et al. Generally, data from historical surveys are usually not comparable with recent surveys due to differences in gear and vessel characteristics as well as sampling procedurThe Cape Verde coastal ecosystem, K.

Table 1 gives a list of some recent international surveys undertaken in Cape Verde, the results of which have been essential for the present study. The revised Ecopath model concerns the continental shelf system for the period to We assume a homogeneous area of 5 km2, which is the estimated area of the continental shelves around the islands.

Also, we do not take into account the oceanic waters between islands, considering them to belong to a different ecosystem. Ecologica l groups Thirty one ecological groups were defined, i. Input and estimated parameters of the Cape Verde Ecopath model. Previous studies undertook the first steps in this direction, but a number of weaknesses were identified and are dealt with in the present study Coelho and Stobberup ; Stobberup and Coelho Thus, we have revised the model through the reformulation of the ecological groups, making the model much more specific for Cape Verde, and undertaken an in-depth bibliographical search for the corresponding diet information.

Another important improvement is the handling of migration in the model, considering that Cape Verde is known to be in the migration route of important species such as tuna ICCAT Pauly 43A total of 99 species wereincluded in the model based on,s characteristics such as diet, mum species and some key parameter d a o ture. To tackle this, we Cape V a terms of re. From ed the definition of benthic s, ec e erotrophic benthos, eter m s their rtaken in the generally ult to s et al.

The aggregation into ecological groups was based on Billfish 4. Table 3 indicates the dominant species in higher trophic level groups see Table 10 for a complete listing of fish constituent Large tun a 3. Quanti tative local information on diet composition was available only for Decapterus macarellus Almada For non-fish groups, local informaassumed that the ecosystem charatrophic functioning and communiinvertebrate functional groups suchand microfauna.

This was also the corresponding diets Tables 2 andNumerous bird studies have beendescriptive e. In the case of marine mammals, tdolphin species. However, in theconsumption estimates as given iinformation on diet for the group,four dominant dolphin speciesDelphinus delphis. We therefore ven in Bundy and use an empirical equation to esthe stud et a gives a good rev lack of quanet altitative inf rmation, we assume similar production and 98a was a valuable source on Bundy di0.

Other demersal fish 3. Fodiator acutus Sparids 2. We followed the recommendation of Christensen et al. This was the period of implementation of the statistical collection system and the high estimates given appear to have been a result of errors in extrapolation. These errors are apparent when considering catches by island. In order to correct for this, the strategy adapted was to adjust the total catches by island and applying the species ata available for to This revision was based on several references, the result of ted in Table 5 Carvalho ; Hanek et al.

Matrix of proportions by prey item with predators on horizontal axis and prey items on vertical axis. Import values indicate proportion of diet from foraging outside the system. Estimates of thevon Be ffy growth param er w we o ng, making ff lt toapp t n empiri equ n ofPauly 1 we used the empiricalequatio roese and Bi hlan imate natural moM - 0.

Conside the relative dominance ofpecific fish species in each group, the parameter et composition were est d as we ed averages b ed ass estimates for thedemersal in particular. This period was characterized by a predominantly artisanal fisheries and low leve of m rization. It this period a i le on sy em w established Shimura and the fir y ys were ta r g at of fis es and biomass for different f t sen tudy e t ti in or a s ulat of ecosystem dynamics from the period to the esentConsiderin h Cape e e it d a o tal ar e under a strong oce e.

Migratory ble5 stim fish y group and fishing fleet Artisan s - handlin Artis al nets — seinegillne Indu ial — p and , sein. Sha g ind tes incre d val o acc moda unide fied c hes. Instead, n proposed by F no to est rtality M: I stead, we allo to ate th es, ng t predatiortal ty as well as otho of 0. Thus, the pre t s may s rve as he star ng po t f im ionpr. Thus, we delimit the model to , catches, and trophic interactions.

This is important as it ral, based on the underlying diet matrix and the fisheries ble to split the large tuna group into yellowfin and skipjack tuna, i. However, available data on potential catches and annual production are Another dominant group is the small pelagics group composed primarily of scad mackerel Decapterus carellus. The available b mass estimate of 65 t A comparison of total biomass for these groups Table 2 presents some of the basic input parameters of the model as well as the values estimated by the model.

Biomass estimates were available only for demersal fish groups, small pelagics, and large tuna, i. It would have been desiraTable6. Shading indicates increased value to accommodate for unidentified catches. Ndiscards are assumed for the period to A tuna biomass estimate of 2. There is considerable uncertainty attached to this tuna biomass estimate, but it is crucial to limit this parameter as tuna are very dominant in the system.

Scad mackerel should form its own distinct group in the model, considering their diet, importance in the pelagic food web, and their economic importance, but this was not possible with the information at hand. More temperate Atlantic islands, e. As there is a considerable source obiomass estimates and diet composition of fisbenthos groups, the results seem reasonablesetting. However, there appears to be an e , possibly in relation to the unit used.

For fish groups, diet comestimated from information available in thespecies, and preferably for similarly tropical arData obtained from the literature were stamajor groups e. This matrix of lower trophic level practically ready for use in the model as itsecosystem components at this level was similof the components, educated guesses of the pspecific group preyed upon by other groups had as it was not possible to provide better esabsence of local studies on food composition.

One way of determining whether the scomposition is reasonable is to analyze mortalities by predation and fishing.

International African Bibliography

Tableresulting mortalities, given the specified dietThese predation mortalities appear reasonablbe pointef variation on h ror rp by e le Weighing procedure adopted foratios are ositions were literature,as Tabardized into ytoplanktoof major fgroups was definition of. For the rest oportion ofto bemates in the pecifiehe resu 7 gives the composit mion. As m ioned ral groups ha lit up a n ious fi roups ity by predation shing a one asp t that s s out hing on th s seen th alues shing mortality values for g oups s a c pred s and tent.

Table 8 gives total mortavery clearly is the relatively light effect of fimortality. The only exceptions are the fishingdemersal predators, as well as tuna to some ewhere fishing pressure is so low that it can almA revision of the fisheries statistics was undertaken for the period to specified for the model. This resufisheries statistics in these years and further revision may yield even lower catch estimates Stobberup et al.

In the interest of placing a limit on the primary productivity in the waters of the Cape Verde Archipelago, an attempt was made to estimate production and biomass. Mixed trophic impact analysis, as defined by Christensen et al. Pauly 49system Figure 3. The resulting pattern reinforces many of tartisanal net fishing generally had a very small effect on the dthe artisanal nature mostly handlines of the fisheries in the negative effects on target species such as pelagic and demersal handline fishing effects on seabirds and flatfihe points already discussed. Industrial and i ith e ing had sh are uncertain as and unreported catches.

The positive effect of small pelagics on t pelagic predators as well as in the ortanc mack care in d tive effect on prey, i ting t of large ar t ela s n ffects on moray eels and rays by e speci et d n the axis. G fferent groups, which is in agreement warly s. On the other hand, the artisanal these catches were assumed by-catchhe top e of scad erel D. P gic shark positive e model, given th fied di prey items dow vertical roups 6 7 8 9 10 — — — 0. Large tuna generally hatheir importance as the dominant predators.

However, the nefishing is the result of tuna preying on small pelagics that arehad a negative effect on other large predators, which resulted ifeeding on their predator, small sharks. Predation mortalities for the higher trophic levels of thecomposition. Predators are arranged along the horizontal axis an Prey 1 2 3 4 51 Sea birds — — — — — 2 Mammals — — — — — 3 Billfish — — — 5 Pelagic predators 0. On the other hand, the small effects of jacks and small tuna, which are important groups in the system, appear to be related to their feeding at lower trophic levels.

Lower trophic level groups included in to simplify the graph, but also ecau thei fects on ighe levels were obvious. Phytoplapositive effects on zo lank w ch in turn resulted in positive effects o l elagics and all dators. The benthic invertebrate groups had a positive effect on thei the relat een these grou wha sevetrop amongst ben Cap be consideimilar to other tropical areas in terms of trophic functioning and community strucDemersal and reef fish fauna in Cape Verde were found to besimilar to other tropical a asbut there appear to be eessential differences in acorals and seaweed are ominor importance and abenthic primary productivitydepends mainly on calca ualgae van der Land However, we must stress t odel particular, which were base nsurvey information and the i statisti m.

Gro Nam l Ar nal L t nal N otal were not Figure 3 in order b se r ef h r trophicnkton had op ton, hin sma l ptheir prer predators as expected, but cionship betwps was complicated byt appeared to be ral hic loops thethos groups. Impacted a d alo t a im tin wn the ve cal ax rou ower troph levels ve be om d lify th gure text e groups gure 3. Mixed trophic pacts of mode groups in t Cap rde talsys m for the 81 to 1 G ps at l ic ha enitte in order to simp e fi see on thes. Pauly 51to 56 t, appear to be overly optimistic, especially for demersal specieslee.

Total catches shows an of more efficient vessels catches remains around reas, such as Senegal, and. Includes estimates of n empty cell indicates that no ferring to a different species, Diet referencesMorato et al. These assessments were based on production estimates from other aadjusted to consider the likely lower productivity in the Cape Verde ArchipelagoTable 1 0.

Diet references with an asterisk indicate that information rbut the same Genus, was used. Pauly 53A simple calculation based on the model results would be a good way of assessing previous estimates of potential yields. But this simple calculation does not take into account the biomass of species that are of no commercial value. Although an upper limit of 56 t of potential yield is too high, a doubling of catches appears to be feasible.

However, the ecosystem effects of such an increase has to be studied, considering the effects on each of the ecosystem components and including direct and indirect effects as well as the effects on the more vulnerable groups. An important next step is to simulate the effects of increasing fishing pressure in the Cape Verde coastal ecosystem. Time series data on catches and fishing effort are essential for such a study covering the period to and may help to determine whether the model components have been correctly specified or if adjustments are necessary, in other words a calibration process.

Thus, we hope to contribute to the process of introducing the ecosystem approach to fisheries assessment in Cape Verde, which can lead to useful indicators for management purposes. Monteiro, INDP, for providing crucial information on diet composition for several species and complementary information on surveys undertaken in Cape Verde; Carlos Monteiro for insight into the statistical collection system in Cape Verde; Daniel Pauly and Villy Christensen for valuable advice. Relation between production and biomass. Life history of scad mackerel, Decapterus macarellus Cuvier , in the waters off the Cape Verde Islands.

Haskoli Islands, Liffraediskor, Reykjavik, Iceland. Belize City, Belize, December The fishery of Cape Verde. Long-term variability in the food chains, biomass yields, and oceanography of the Canary Current Ecosystem, p. Stress, Mitigation, and Sustainability. Vie Mileu 43 The diets of fish in three south-western Cape estuarine systems. Feeding pattern of Scorpaena porcus and S. Production studies in Canary Island waters. Bravo de Laguna, J.

Lilly and Shelton, P. A mass-balance model of the Newfoundland-Labrador Shelf. On steady-state modelling of ecosystems, p. Trophic Models of Aquatic Ecosystems. Cephalopods, blue sharks and migration. Regime alimentaire de quelques especes. Global markets, fisheries and development, workshop held on March , Chr. The state of world fisheries and aquaculture, Resources, fishing and biology of the tropical tunas of the eastern Central Atlantic.

The Azores Archipelago, , p. Fisheries Centre Research Reports 9 4. University of c Bight. EU Fisheries Research Initiative. Ornithological bibliography of Cape Verde Islands to inclusive - Bibliographie ornithologique de Lon f West African demersal fish. II Report, Icelandic Intern. Survey of demersal fish resources in the kjavik. Fischerei-Forschung, Rostock 25 1: Feeding of the large-eyed dogtooth, Dentex macrophthalmus, and Spanish bream, Pagellus acarne, from the Central-Eastern Atlantic Ocean.

On the feeding of AlFonteneau, A. Empirical relationships to estimate asymptotic length, length at first maturity and length at maximum yield per recruit in fishes, with a simple method to evaluate length frequency data. Espectro alimentario del patudo Thunnus obesus en la primavera austral de en el Pacifico sur oriental, p. Distribution, abundance, reproduction, food habits, age, and growth of round scad, Decapterus punctatus, in the South AtlantiHallier, J. Food partitioning amonMediterranean seagrass beds. Food habits, seasonal abundance, size, and sex of the blue shark, Prionace gluaca , in MCalif.

Keystone predators in the Central Pacific. Ecosystem approaches for fisheries management. Alaska Sea GKoranteng, K. Review of the Canary Current and Guinea Current large marine ecosystems, p. Dakar, Senegal, April A summary survey of the food oLonghurst, A. Ecological geography of the Sea. An estimate of global primary production in the ocean from satellite radiometer data. Survey of demersal fish resources in the waters off CapReykjavik.

Summary of information on species, Icelandic Intern. Food consumption of yellowfin tuna, Thunnus albacares, in Sri Lankan waters. Stomach contcollected along the south Atlantic and coasts of the United States. Mo ishes from Mu s in Jamaican waters, p: Caribbean coral Nag 7 2: Coral RanReiRog Relationships among yellowfin and skipjack tuna, their prey-fish and plankton in the tropical western Indian Ocean.

Bothidae in the central Meidterranean Sea. Constructing an Icelandic marine ecosystem model for using a mass-balance approach, p. Predation patterns of demersal teleosts from the Cape south and west coaBenthic and epibenthic predators. Ground fish survey in the waters off Cape Verde. Trophic relationships and feeding habits of demersal fthe Azores: Feeding habits, seasonal and ontogenetic diet shift of blacktail comber, Serranus atricauda, from the Azores, north-eastern Atlantic.

The composition and magnitude of line catchereef resources. Field metabolic rate and food requirement scaling in mammals and birds. The demersal smhandline surveys A preliminary handline survey of the artisanal resources of the Republic of Cape Verde, A quantitative model of the trophic interactions. Trophic models of aquatic ecosystemPalko, B. Synopsis of the biological data on dolphin-fishes, Coryphaena hippurus Linnaeus and Coryphaena equiselis LinnaeusPalomares, M.

Predicting the food consumption of fish populations as functions of mortality, food type, morphometrics, temperature and salinity. Marine and Freshwater Research 49 5: Feeding interactions between two sympatric species Pagrus pagrus and Phycis phycis around Kastellorizo island Dodecanese, Greece. Oceanic food webs and economic productivity. Improved construction, parameterization and interpretation of steady-state ecosystem models, p. Trophic models of aquatic Pauly, D. Fishing down marine food webs. Model of a coral reef ecosystem. Cetaceans of the Cape Verde Archipelago.

Diets of NW Atlantic fish and squid. Diets of trawled predatory fish of the Gulf of Carpentaria, Australia, with particulareference to predation on prawns. Results of the 5th Symposium: Fauna and Vie erspectivas, p. Gut content analysis of fishes sampled from the Gulf of Thailand. Food and feeding habits of swordfish, Xiphias gladius, in the western north Atlantic.

Occurrence and feeding of three shark species, Carcharinus brachyurus, C. Life history Linnaeus, and Mustelus palumbes Smith, Pisces: The feeding ecology of skates Batoidea: Food and ecology of the swordfish Xiphias gladius in the western North Atlantic Ocean wi th estimates of daily ration. A preliminary Ecopath mode l for Cape Verde: Steps towards a better understanding of local ecosystem dynamics. A review of the Cape Verde fisheries ; a characterization including influencing factors and historical evolution. A survey of the fish resources in the coastal waters of the Republic of Cape Ve rde, November Reviews in Fish Biology and Fisheries 7: West African coastal ecosystems, M.

The shelf supports a very rich fauna, which is extensively exploited by both artisanal and industrial fisheries. This, therefore, warrants sustainable exploitation of the resources. Classical research tools were in the past used to study these important resources. This study proposes the use of a model based on trophic relations between and within functional groups of the Senegambian ecosystem.

The data originates from recent publications referring to the s and information available from research institutions working in this region. The results emanating from the Ecopath with Ecosim model are discussed and compared with those obtained from studies conducted in similar ecosystems. The Ecosim simulations from [missi ng word? An addendum, contributed by Birane Samb, on the extension of this model for the period from to is provided at the end of this contribution. La superficie totale est de 27 km2. Mendy 62annuelles de 10 t. La composition alimentaire comprend essentiellement les poissons et le zooplancton Diatta et al.

Fridtjof Nansen en Saetersdal et al. Les captures moyennes annuelles se situeraient autour de 90 t. La sardinelle ronde et la sardinelle plate: La valeur de biomasse moyenne pour la sardinelle West African coastal ecosystems, M. Pauly 63ronde est de t et t pour la sardinelle plate. Le macrobenthos est important pour la no urriture des poissons demersaux mais les connaissances acquises sont assez sommaires.

Mendy 68Figu re 4. Growth rate of Raja clavata in the north east Irish Sea. Age and growth validation of newborn sharks in laboratory aquaria with comments on the life story of the Atlantic sharpnose shark. Minimal fish predation for the pink shrimp Penaeus notalis in Senegal West Africa. A guide to the Ecopath II software system version 2. Seabird consumption and production in the Benguela and Western Agulhas ecosystems. De la Cruz-Aguero, G.

A preliminary model of Mandinga lagoon, Veracruz, Mexico, p. Exploitation, gestion et conservation des stocks de requins: Euthynnus alletteratus, Sarda sarda et Scomberomorus tritor. The environment in the Eastern Tropical Atlantic, p. Resources, fishing and biology of the tropical tuna in the Eastern Central Atlantic. The potential role of mass balance models for the management of upwelling ecosystems. Seasonal changes in the Peruvian upwelling ecosystem, p. Comparing trophic flows in the Southern Benguela to those in other upwelling ecosystems. A preliminary biomass budget for the northeastern Venezuela shelf ecosystem, p.

World review of interactions between marine mammals and fisheries. An ecosystem model of Monterey Bay, California, P. Comparative climatology of selected environmental processes in relation to eastern boundary current pelagic fish reproduction, p. Proceeding of the experts consultation to examine changes in the abundance and species composition of neritic fish resources. Paula e Silva, R. The Maputo Bay ecosystem Mozambique , p. A preliminary compilation of fish length growth parameters. Gill size and temperature as governing factors in fish growth: Once more on growth comparison in fish and invertebrates.

Survey of the pelagic fish resources off North West Africa. Seasonal growth, mortality, recruitment pattern of Sardinella maderensis off Senegal, p. Contributions to tropical fisheries biology. Fish and Fisheries 1: FAO species identification sheets for fishery purposes. Field guide to the commercial marine resources of the Gulf of Guinea. Par t I Senegal-Gambia. Pauly 73 Tableau 2. Samb 74Figur e 1. Report of the ad hoc working group on coastal demersal stocks from Mauritania to Liberia 26 N to 5 N.

Accompanied with a poster presentation and abstract; see http: Report of the Guinean Trawl Survey. These change consist of a reduction of the biomass of longer lived fishes, particularly in shallower waters, and in conjunction with environmental fluctuation, the creation of opportunities for invasive species of fish triggerfish Balistes carolinensis and invertebrates e. The relative impacts of fishing and environmental changes in generating these outbursts are difficult to disentangle. It is evident, however, that the effort jointly exerted by several Ghanaian fleets onto their supporting fisheries resources is excessive and that the country would benefit from a reduction of that effort.

As in most other parts of the world Pauly et al. Long-term trends in demersal fishery resources of Ghana in response to fishing pressure, p. Also available in Proceedings of the International Symposium on Marine fisheries, ecosystems, and societies in West Africa: Demersal fishery resources of Ghana, K. Ko ranteng and D. Pauly 76 sudden appearance of the scallops Chlamys purpuratus and Pecten jacobeus in coastal waters Mehl et al. This contribution describes these and other fluctuations, with emphasis on the role of the industrial fisheries as the main driver for change, thus complementing the brief account of Alder and Sumaila Artisanal fishing in lagoons and estuaries, though locally involving substantial number of fishers and their small scale gear gill net, throw net, weirs, etc.

Sakumo lagoon, near Tema, studied in some detail in Pauly , has much deteriorated since Ntiamoa-Baidu ; Pauly , and this appears to be representative of other lagoons along the Ghanaian coast Entsua-Mensah However, nationwide catch data are lacking which could be used to evaluate how the lagoon fisheries are performing, relative to the other Ghanaian fisheries. The canoe fleet deploys various fishing gear types, notably beach seines, handlines and bottom set gillnets to catch demersal species, and purse seines to catch small pelagics, foremost Sardinella aurita. Consequently, the canoe fishery is much affected by the natural fluctuations of the sardinella.

These fluctuation, and their impact on the fisheries are been previously discussed in some details in Pezennec and Koran teng and hence we abstain here from discussing this fishery further. The inshore fleet consists of multipurpose vessels using purse seines to catch small pelagics during the upwelling seasons December-January and July-September.

For the rest of the year, these vessels, except those lacking strong engines, are used for bottom trawling. The fleet grew from two vessels in to over operational units in Mensah and Koranten g ; K oranteng However, the fleet has since declined in importance, as most of the vessels are old and barely seaworthy; only inshore vessels operated in The first Ghanaian industrial fishing trawlers were acquired about four decades ago principally for fishing in the productive, if distant waters of countries such as Angola and Mauritania Kora nteng, These vessels were forced to return, and to start operating in Ghanaian waters when, in the mid s, these countries claimed miles Exclusive Economic Zones.

With the exception of the tuna fishing fleet, all the fleets mentioned above thus operate in about the same area, and target similar species. This generates conflict among the fleets, especially between the canoe and the trawler fleets including the shrimpers , with the latter very often destroying fixed nets set by the former. Pauly 77 Figure 1 shows the changes in the effort of inshore and industrial trawlers from to As may be seen, this portrays a persistent rise in industrial trawling effort and a decline of inshore vessels.

Figure 2 shows the annual landings of demersal fishes, molluscs and crustaceans by the inshore and industrial fleets, for the period , as compiled from by the Marine Fisheries Research Division MFRD , in Tema, Ghana, and supplied to FAO. This shows consistent growth in landings until the mid s, followed by stagnation and decrease in the last decade. Koranteng , Figure shows the calculated values, trend and seasonal variation of catch per effort by inshore trawlers for the period , considering only demersal species.

Catch per effort increased in the mids, but declined since, indicating that the resources exploited by these trawlers are being overfished. This is here confirmed by Figure 3, documenting trends in the abundance of demersal resources as a function of depth.

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