Habitat and Biology
Climatic zone: Temperate Bottom type: Unspecified Depth zone: Coastal_0_50m ; Shelf_50_200m Horizontal distribution: Neritic ; Oceanic Vertical distribution: Pelagic
Geographical Distribution
Jurisdictional distribution: Shared between nations
Resource Structure
Considered a single stock: No
The stock identity as given in the 2005 report of this Work Group (FAO, 2007) is maintained. In the subregion, the West African Bonga shad (
Ethmalosa fimbriata) are mainly concentrated in Senegal, the Gambia and Mauritania.
Exploitation
The bonga is an element of socioeconomic importance and are exploited by fishing communities mainly in Gambia, Senegal and Mauritania. It is the single most important main small pelagic species constituting about 72% of total catches in Gambia in 2007. In Senegal, bonga is mainly fished by artisanal fishermen in the area of Saloum (southern Senegal) using surround gillnets. In Mauritania, the fishery was recently developed to mainly feed the fishmeal factories. As a coastal and estuarine species, bonga is exploited by artisanal fisheries.
CatchAlthough fluctuating, the total catches of bonga in the region have been declining from nearly 33 000 tonnes in 2005 to a little over 21 000 tonnes in 2007. A decreasing catch levels were observed for the Senegalese bonga fishery too. From information received, certain bonga boats from Mbour, Senegal land their catches in the Gambia where they fetch higher value for it. In the Gambia, catches of this species have from 1996 to 2005 been relatively stable fluctuating around 39 000 tonnes with an overall decreasing trend. The total catch in the Gambia nearly stabilized around 13 000 tonnes in 2006 and 2007 with a five year average of nearly 17 000 tonnes.
Until recently, bonga constitute bycatch in Mauritania, it is now being targeting bonga for fishmeal. Catch statistics have been available since 2000, however the reported catches until 1999 were very low and may be due to the fact that they are estimates from a group of species. The highest catches reported in Mauritania was 13 000 tonnes in 2002. It was observed that the same catch level (4 545 tonnes) was provided to the working group for 2005 and 2006 respectively. Important to note was the sharp decrease to 633 tonnes in 2007. This situation was explained to be a result of the lumping of bonga with other species. The Working Group took note of the recent development of the bonga fishery in Mauritania.
Recent developmentsThe recent changes noted are the development of biological and statistical monitoring schemes being implemented in Mauritania and the Gambia. In the Gambia, the scheme started since December 2007 with the assistance from the Gambia Artisanal Fisheries Development Project (GAFDP). Also in Mauritania, bonga is being fished for fishmeal production thus attracting an increasing effort into the fishery.
Assessment
Data
Data qualityThe only data available to the working group is total catches and effort (surrounding gillnets) of the Senegalese artisanal fisheries subsector and therefore no exploratory analysis was done.
Assessment Model
Type: Biomass-aggregated
The Schaefer logistical production model implemented on an Excel spreadsheet was used for the assessment of the
Ethmalosa fimbriata stock in the subregion. The model is described in detail in Appendix II. Another Excel spreadsheet based on the model was used make projections of catch and abundance for the following five years (Appendix II).
Overall Assessment Results
An attempt was made to make an assessment of the bonga stock using available data but the model did not provide reliable results.
Projection
The Working Group was not in a position to make projections for bonga.
Scientific Advice
Future researchFollow up on last year’s recommendationsApparently, no biological data on bonga was collected in the region 2007, but the recommendations with respect to the collection of effort data in the Gambia and the establishment of biological sampling schemes were being implemented and is expected some data will be available to the Working Group in the next assessment meeting.
This year the Working Group therefore recommends:
- Senegal is urged to continue their biological sampling of bonga and should investigate the possibility of obtaining separate effort data for the ethmalosa gillnets.
- Mauritania should improve statistical and biological data collection on E. fimbriata to enable better analysis of the status of the stock.
- A joint biological sampling work should be carried out between and the Gambia and Senegal.
- To encourage studies (higher level) on the distribution and biology of the bonga.
for Management considerationsDespite lack of adequate data for the assessment of the bonga, the Working Group noted the annual decrease in total catches since 2002. As a precautionary measure, the effort in Senegal and Gambia should not exceed effort level of 2007.
Biological State and Trend
Exploitation rate: Not applicable Exploitation state: Uncertain
Abundance level: Not applicable
Source of information
FAO Fishery Committee for the Eastern Central Atlantic/Comité des pêches pour l’Atlantique Centre-Est. “Assessment of Small Pelagic Fish off Northwest Africa” Saly,
Senegal, 6-15 May 2008.
“Rapport du Groupe de travail FAO/COPACE sur l’évaluation des principales espèces de petits pélagiques au large de l’Afrique nord-occidentale”
Saly, Sénégal, 6-15 mai 2008.
Rome, FAO . 2008.
.
Bibliography
The bibliographic references are available in the report included in "Source of Information".
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