Habitat and Biology
Climatic zone: Unspecified. Bottom type: Unspecified. Depth zone: Coastal (0 m - 50 m); Shelf (50 m - 200 m); Slope (200 m - 1000 m). Horizontal distribution: Unspecified. Vertical distribution: Pelagic.
Jurisdictional distribution: Shared between nations
Considered a single stock: No
Sardinellas caught in the southern CECAF Area from Guinea to Angola are composed of two species, the round sardinella (Sardinella aurita) and the flat sardinella (Sardinella maderensis). The surveys carried out in the CECAF area show that the two species are found in a vast area stretching from the southern Moroccan stock to south of Angola. The FAO/CECAF Working Group for the moment has agreed on the existence of four stocks for these two species in the Southern CECAF area. These are the northern (Guinea and Sierra Leone), western (Côte d’Ivoire, Togo, Ghana and Benin), central (Nigeria and Cameroon) and southern (Gabon, Congo and Angola).Southern stock (Gabon, Congo and Angola)
As no Gabonese scientist was present in the meeting, no data is provided for this country. The dominant species off Congo is S. maderensis
. While this species occurs all year round, S. aurita
is most abundant between May and September. Off Congo, the species are exploited by both artisanal and industrial fleets. Surface gillnets operated from canoes are employed in the artisanal fishery while the industrial fleet use pelagic trawl. The canoes are of a LOA of 7–12 m while the pelagic trawls are of 16–24 m in LOA and powered by engines of 400 hp. S. maderensis
is also the dominant of the two species off Angola and occurs in coastal waters, whereas S. aurita occurs offshore. The abundance of sardinellas is linked to the upwelling periods. They are exploited by both the artisanal and industrial fleets. The artisanal canoes are between 5–14 m in LOA and powered by outboard motors of 40 hp. The pelagic trawlers, purse seiners and demersal trawlers all exploit the sardinellas. While the pelagic trawlers and purse seiners target the species, they are bycatch in the demersal trawlers.
The Schaefer logistic production model was used on an Excel worksheet.
The input data was catch and effort data on Sardinella spp. from the artisanal and industrial fisheries for the period 1995–2005. The CPUE of the R/V DR. FRITDJOF NANSEN from Angola was used in the assessment.
Overall Assessment Results
The model fitted reasonably well for all the above stocks although in the case of Sardinella spp. (south) the R2 values were low. A summary of the results of the assessments is presented in Table 1.
Table 1: Summary of the state of the stock
|Sardinella spp. south/CPUE_AngoNansen/
Bcur/B0.1: Ratio between the estimated biomass for the last year and the biomass corresponding to F0.1.
Fcur/FSYcur: Ratio between the observed fishing mortality coefficient during the last year of the series and the coefficient that would give a sustainable yield at current biomass levels.
Fcur/FMSY: Ratio between the observed fishing mortality coefficient during the last year of the series and the coefficient giving maximum long term sustainable yield.
Fcur/F0.1: Ratio between the observed fishing mortality coefficient during the last year of the series and F0.
The main limitation to the assessment is non-availability of data for some countries in the region. In the north, Sierra Leone has a very short data time, while data for Côte d’Ivoire was not available for the western stock. With the exception of S. maderensis (west), the current biomass of the different stocks is less than the biomass at B0.1. The current fishing effort is greater than fishing effort at MSY and if effort is not reduced the stock level will decrease further in the future.
Scientific AdviceFuture research
for Management considerations
- Biological sampling intensification.
- Continue with Nansen surveys to obtain fisheries independent data.
- Adoption of a sampling programme for the commercial fleet.
As a precautionary measure, do not increase catches of this species.
Biological State and Trend
Exploitation state: OverexploitedExploitation rate: Fcur/F0.1: 169 %
Abundance level: Bcur/B0.1: 63 %
Source of information
FAO Fishery Committee for the Eastern Central Atlantic/Comité des pêches pour l’Atlantique Centre-Est. “Report of the FAO/CECAF Working Group on the Assessment of Small Pelagic Fish – Subgroup South” Limbe, Cameroon, 25 September–1 October 2006
“Rapport du Groupe de travail FAO/COPACE sur l’évaluation des petits poissons pélagiques – Sous-Groupe Sud” Limbé, Cameroun, 25 septembre-1er octobre 2006
Rome, FAO . 2009
The bibliographic references are available in the report included in "Source of Information".