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

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INCOFISH WP7Simple indicators for sustainable
fisheries Lima, 4-7 december 2006

• Reports Activities
• By
• Birane SAMB and Fambaye NGOM
• Centre de Recherches Océanographiques de Dakar
  Thiaroye
• Dakar Sénégal

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

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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

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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.

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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).

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Differents step of work

• Database
• List of species with biological parameter and
  reference
• Fish ruler
• Calcul of simple indicators for some species

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DATA BASE
Length frequency from catches
Length frequency

Length frequency from survey

Other biological parameter
Lm growth parameter L max
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List of species with biological parameter
(example of output)
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Fish ruler

• SEE FILE

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Calcul of simple indicators for some important
species in Senegal
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Material

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

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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.

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ANALYSE ON THE STATE OF SOME DEMERSAL SPECIES
CAUGHT BY SENEGALESE FISHERIES USING SUSTAINABLE
INDICATORS

• Pagellus bellotii
• Sparus caeruleostictus
• Galeoides decadactylus
• Pseudupeneus prayensis

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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
with size 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
bellotii in the catches
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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
caeruleostictus 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 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
caeruleostictus in the catches
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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
decadactylus 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 fishes is below
  the target of 100 .
• The annual percentage of fishes with the optimal
  size declined since 1993 to 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
decadactylus in the catches
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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
prayensis 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 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
prayensis in the catches
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Thanks for your attention