GILL NET SAMPLING STANDARDISATION IN LARGE RIVERS OF FRENCH GUIANA (SOUTH AMERICA).
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.