| Summary: | In this paper is analyzed the sampling efficiency of repeated batteries of mixed
gillnets mesh size from 15 to 70 mm. The study was conducted in three French Guiana
rivers : the Sinnamary, Comté and Malmanoury rivers. Efficiency of sampling methods is
one of the problems faced by freshwater ichthyologists. If the choice of one approach must
consider its efficiency and cost/profit rates for a determinate level of accuracy, the abiotic
characteristics of the environment sampled has also an important role in this process.
Large rivers, like those sampled in French Guiana, present specific abiotic characteristics
that prevent the large use of non-selective sampling methods like electrofishing or
rotenone poisoning. Differently, other sampling gear such as gillnets is used frequently.
This kind of gear presents known bias problems related to fish size or species. However,
bias can be diminished through the use of mixed gillnets mesh size, which efficiency was
previously determined. Results of Principal Component Analysis (PCA) suggest that gillnet
mesh size 15 to 35 mm are the most efficient in sampling fish fauna in the rivers sampled.
Regarding the number of repeated batteries, the analysis of Catch Per Unit of Effort
(CPUE), species richness, sample structure (rank correlation) and the examination of their
variance suggest that the use of three batteries gives a good estimation for the fraction of
the fish community sampled.
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