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INCOFISH : WP7 Simple indicators for sustainable fisheries Lima, 4-7 december 2006

INCOFISH : WP7 Simple indicators for sustainable fisheries Lima, 4-7 december 2006. Reports Activities By Birane SAMB and Fambaye N’GOM Centre de Recherches Océanographiques de Dakar Thiaroye Dakar Sénégal. Senegal is located in North West Africa. MAP of AFRICA. Atlantic Ocean.

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INCOFISH : WP7 Simple indicators for sustainable fisheries Lima, 4-7 december 2006

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  1. INCOFISH : WP7Simple indicators for sustainable fisheries Lima, 4-7 december 2006 Reports Activities By Birane SAMB and Fambaye N’GOM Centre de Recherches Océanographiques de Dakar Thiaroye Dakar Sénégal

  2. Senegal is located in North West Africa MAP of AFRICA Atlantic Ocean Map of Senegal

  3. Importance of fisheries sector in Senegal • 11 500 000 habitants with more than 50% of population in coastal zone • 700 km coastline, with continental shelf area of 24 000 km2 • First sector of export

  4. Importance of fisheries sector in Senegal (suite) • Takes an important place in the supply of animal proteins • 600 000 indirect employments • 15% of the working population • Annual consumption 26kg/year/ha where in Africa the mean consumption is 8.2 /year/ha

  5. Fisheries • The artisanal fishery consists of motorised canoes using a variety of gear. Essential catches are done by artisanal fisheries • The industrial fishery is undertaken by trawlers or purse seiners, some of which are foreign vessels operating under commercial agreements.

  6. Marine Resources • Marine resources are characterized by their diversity • (i) Pelagic resources consisting of clupeids engraulids, carangids, scombrids, tuna and sharks. These species constitute up to 75% of the stocks. (ii) Demersal resources which have a higher economic value include crustaceans (shrimps, lobsters, and crabs), molluscs, cephalopods as well as bony fish (serranids, lutjanids, sciaenids, mullets, etc.), rays, and sharks. (iii) Coastal and estuarine resources, comprising bivalves and fish (cichlids, mullets, etc).

  7. Differents step of work • Database • List of species with biological parameter and reference • Fish ruler • Calcul of simple indicators for some species

  8. DATA BASE Length frequency from catches Length frequency Length frequency from survey Other biological parameter Lm growth parameter L max

  9. List of species with biological parameter (example of output)

  10. Fish ruler • SEE FILE

  11. Calcul of simple indicators for some important species in Senegal

  12. Material • Length frequency data from catches of artisanal fisheries • Biological parameter from database • Indicators_spreadsheet_tool.xls

  13. Method • Lm is Length at first maturity and refers to the length at which 50% of the individuals in a population have reached reproductive maturity. • L90-100 is the length where 90-100% of individuals in a population have reached reproductive maturity and is calculated as Lm x 1.14 • Lopt is the length at which the fewest individuals of a population have to be harvested in order to reach the maximum biomass. The optimum harvest range is that from 10% lower than Lopt to 10% higher than Lopt (Lopt ± 10%) • Lopt = Linf * (3 / (3 + M/K)) • Mega-spawner is an individual who has reached a size at least 10% larger than Lopt for a population.

  14. ANALYSE ON THE STATE OF SOME DEMERSAL SPECIES CAUGHT BY SENEGALESE FISHERIES USING SUSTAINABLE INDICATORS • Pagellus bellotii • Sparus caeruleostictus • Galeoides decadactylus • Pseudupeneus prayensis

  15. Read Pandora Pagellus bellotii Most fish are captured after their first size of maturity. But these fish were captured before the economic optimal size. The large specimens withsize 10 % larger than the optimal size miss almost in the captures. Figure 1. Length frequency of Pagellus bellotii landed from 1990 to 2003 in Senegal where Lm is the length of first maturity, Lopt is length with maximum yield per recruit can be obtained and Lmax is the maximum size reached during this period • The annual percentage of mature fish in the captures is close to or approaching the target of 100%. • The annual percentage of fish with the optimal size in the captures is relatively low compared with the target of 100 %. • The annual percentage of mega-spawners is below 30 - 40% representative a healthy structure of age. • It would be more interesting to capture fish with a higher size to approach the optimal weight Figure 2. Annual percentages of fish mature, fish at size optimal and megaspawners of Pagellus bellotiiin the catches

  16. Bluespotted seabream Sparus caeruleostictus Most of fish are caught before their first length of maturity. Fish are caught before the optimal size. Mega-spawners miss almost in the captures. Figure 3. Length frequency of Sparus caeruleostictuslanded from 1990 to 2003 in Senegal where Lm is the length of first maturity, Lopt is length with maximum yield per recruit can be obtained and Lmax is the maximum size reached during this period • The annual percentage of mature fishes is very low compared with the target of 100%. • The annual percentages of fishes with the optimal size and mega-spawners in catches is very low. • This very weak value is an indication of depletion of stock. • These indicators suggest that the stock is in a state of overexploitation Figure 4. Annual percentages of fish mature, fish at size optimal and megaspawners of Sparus caeruleostictusin the catches

  17. Small captain Galeoides decadactylus Most of fishes are above the size for first maturity and in the range of the optimal size where the maximal yield can be obtained. Mega-spawners are little represented in the total catches. Figure 5. Length frequency of Galeoides decadactyluslanded from 1990 to 2003 in Senegal where Lm is the length of first maturity, Lopt is length with maximum yield per recruit can be obtained and Lmax is the maximum size reached during this period • The annual percentage of mature fishes is below the target of 100 %. • The annual percentage of fishes with the optimal size declined since 1993to reach 18 % in 2003. • The annual percentage of mega-spawners is below 30 – 40 % representative a healthy structure of age. • In spite of the increase of mature fishes in catches, indicators suggest that the stock of the small captain is also threatened by an overexploitation. Figure 6. Annual percentages of fish mature, fish at size optimal and megaspawners of Galeoides decadactylusin the catches

  18. West african goatfish Pseudupeneus prayensis The catches are constituted by individuals whose size is in the range length where the maximum yield can be obtained. The mega-spawners are also little represented in catches. Figure 7. Length frequency of Pseudupeneus prayensislanded from 1990 to 2003 in Senegal where Lm is the length of first maturity, Lopt is length with maximum yield per recruit can be obtained and Lmax is the maximum size reached during this period • The percentage of mature fishes is very low compared with the target of 100 %. • However the percentage of fish with the optimal size increased since 1990 to reach 80 % in 2003. • But he percentage of mega-spawners is below 30 – 40 % representative a healthy structure of age. • These results suggest that the stock is not in situation of overexploitation . Figure 8. Annual percentages of fish mature, fish at size optimal and megaspawners of Pseudupeneus prayensisin the catches

  19. Thanks for your attention

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