FIRMS - Marine Resource fact sheets - Madeiran sardinella and Round sardinella - Guinea-Bisseau, Guinea, Liberia and Sierra Leone, 2008

Madeiran sardinella and Round sardinella - Guinea-Bisseau, Guinea, Liberia and Sierra Leone, 2008

Marine Resource Fact Sheet

Status of stocks and resources 2009

Madeiran sardinella and Round sardinella - Guinea-Bisseau, Guinea, Liberia and Sierra Leone, 2008

Sardinella maderensis and Sardinella aurita - Northern Stocks

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Food and Agriculture Organization (FAO) – More

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Species:

Sardinella maderensis

Sardinella aurita

Geographic extent of Madeiran sardinella and Round sardinella - Guinea-Bisseau, Guinea, Liberia and Sierra Leone

Map legend

Area Details

Main Descriptors
Considered a single stock: No Spatial Scale: Sub-Regional

Table of Contents

Habitat and Biology - Geographical Distribution - Water Area Overview - Resource Structure - Exploitation - Assessment - Biological State and Trend - Source of information

Habitat and Biology

Climatic zone: Tropical. 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.

Geographical Distribution

Jurisdictional distribution: Shared between nations

Water Area Overview

Spatial Scale: Sub-Regional

Geo References

Resource Structure

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 zone 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 northern (Guinea-Bissau, Guinea, Sierra Leone and Liberia), western (Côte d’Ivoire, Togo, Ghana, Togo and Benin), central (Nigeria and Cameroon) and southern (Gabon, DR Congo, Congo and Angola) (Figure 2.1.1).

Exploitation

The Sardinella aurita occur offshore and are exploited by the industrial pelagic trawlers of Guinea and shrimp trawlers and purse seiners of Sierra Leone. S. aurita is the second most abundant fish after Decapterus spp. in their catches. The shrimp trawlers and the finfish trawlers of Sierra Leone, and Liberia fish the S. aurita and S. maderensis as bycatches. The S. maderensis occur in coastal waters and are exploited by the artisanal canoes of Guinea, Guinea Bissau, Sierra Leone and Liberia. In these countries, the artisanal canoes use ring gillnets, set gillnets, drift gillnets and beach seines to catch these species. Most of the ring gillnet crafts are powered with outboard motors of 15–40 hp.

Catch

The catches of sardinella are shown in Tables 2.2.1a,b,c. Effort is shown in Table 2.2.2 and Figures 2.2.2a,b.

Assessment

Assessment Model

Type: Others

The dynamic production model implemented on an Excel spreadsheet was used (Appendix II).

Standardised CPUE

Results

The model fitted reasonably well to the data. A summary of the results of the assessments is presented in Table 2.6.1a and Figure 2.6.1a.

The results from the assessment indicate that the current biomass of Sardinella spp. is 24 percent above B_0.1. The relationship between the current fishing mortality at F_0.1 is 56 percent, and the fishing mortality is lower than the fishing mortality coefficient that will provide a sustainable yield in the long term.

Table 2.6.2: Summary of the results for the Sardinella spp. in the northern stock

Stock/abundance index	B_cur/B_0.1	F_cur/F_S_Y_cur	F_cur/F_MSY	F_cur/F_0.1
Sardinella spp. (North/CPUE Liberia Industrial)	124%	79%	50%	56%

B_cur/B_0.1: Relationship between the estimated biomass for the last year and the corresponding biomass at F_0.1.

F_cur/F_SY_cur: Relationship between the fishing mortality coefficient observed over the last year of the series and the coefficient that would provide a sustainable yield at the current biomass level.

F_cur/F_MSY: Relationship between the fishing mortality coefficient observed over the last year of the series and the coefficient that would provide a sustainable yield over the long term.

F_cur/F_0.1: Relationship between the fishing mortality coefficient observed over the last year of the series F_0.1.

Discussion

Although the model shows that the stock is not fully exploited, knowledge on the fisheries from the region reveals that Sardinella spp. is fully exploited. As a precautionary measure the catch should not exceed the last year catch of the series. The main limitation to the assessment is non-availability of time series data in the region. Time series data from surveys still remain a problem, but recent survey data in 2008 and 2009 are available for Sierra Leone (not present in the Working Group meeting in 2009). Additionally, Sierra Leone has a very short catch and effort data time series (2002–2007).

Scientific Advice

Future research

Fisheries research should be emphasized for all the regions. Data collection schemes should be improved and effort should be made to collect data on species basis in the artisanal and industrial fisheries.
Intensify biological sampling for better estimates of growth, mortality and abundance indices.
Identification of species especially the Carangidae and Sardinella.
Continue with Nansen surveys to obtain fisheries independent data.
To obtain better abundance indices of the sardinellas below the 30 metres depth contour.
To better understand interactions between the resource and the environment.
Adoption of a systematic sampling programme for the collection of catch and effort data for all fleet.

for Management consideration

It is recommended to maintain the catch of the last years (about 20 000 tonnes) and to regulate the fishing effort especially in the inshore coastal waters where the juveniles are targeted by artisanal fishers. The canoe fleet numbers should be controlled.

Biological State and Trend

Sardinella spp.

Exploitation state: Fully exploitedExploitation rate: Fcur/F0.1: 56%

Source of information

Report of the FAO/CECAF Working Group on the Assessment of Small Pelagic Fish – Subgroup South Accra, Ghana, 19–28 October 2009./Rapport du Groupe de travail FAO/COPACE sur l'évaluation des petits poissons pélagiques – Sous-groupe Sud Accra, Ghana, 19-28 octobre 2009.

http://www.fao.org/docrep/018/i2909b/i2909b.pdf

Fishery Resources Monitoring System