Assessing the Effects of Fishing in Cape Verde and Guinea Bissau, Northwest Africa

Assessing the Effects of Fishing in Cape Verde and Guinea Bissau, Northwest Africa

Kim A. Stobberup, Patrícia Amorim, Virginia Pires, and Vanda M. Monteiro

Assessing the Effects of Fishing in Cape Verde and Guinea Bissau, Northwest AfricaThis is part of Fisheries Assessment and Management in Data-Limited Situations
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Description

The assessment of fishery resources in countries such as Cape Verde and Guinea Bissau is particularly difficult due to data limitations and a lack of consistent time series. Considering these limitations, several techniques were applied, depending on the type of data available. These techniques included nonparametric multidimensional scaling (MDS), abundance-biomass curves (ABC curves), correlation analysis, and general linear models (GLM), which were applied to trawl survey data. Furthermore, mean size of species groups was used as an indicator in the case of Guinea Bissau and time series analysis was applied to the Cape Verde catch statistics.

In Cape Verde, there was no apparent change over time in the structure of demersal fish communities. This is consistent with a gradual increase in fishing pressure over a period of 20 years, which was also observed as a trend for lower mean abundance of demersal fish species in recent years. In contrast, time series analysis of catch data indicates that a shift has occurred with decreasing catches of important pelagic species such as yellowfin and skipjack tuna and increasing catches of small pelagics and neritic tuna as well as some demersal species.

In Guinea Bissau, the effects of area and depth were found to be important in defining the structure of demersal fish communities. In contrast, the effect of time was not apparent. On the other hand, demersal fish abundance and mean size of groups decreased for recent years, from 1989 to 1992 in particular, which was a period of intensive fishing. Furthermore, an effect on the abundance/biomass relationship (ABC curves) was observed for the same period.

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