Title: Gillnet selectivity: A case study in Icelandic lake and marine environments with reference to Cambodian fisheries

Author(s): Makkhen Kheng
Final project
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This study demonstrates the selectivity of different mesh sizes and mesh types for different marine and fresh water fisheries. Three species of fish were chosen for this study: cod (Gadus morhua) and saithe (Pollachius virens) from marine fisheries and brown trout (Salmo trutta), from the inland fisheries. The selection model is expanded by application of relative length (i.e. the ratio of fish length to the mesh size) to obtain the curve for gillnet selectivity. Four kinds of functions are fitted to the data: normal fixed spread, normal, gamma and log-normal with proportional spread. Each fish species was best fitted to a different model: the gamma model gave the best fit to the cod data, the normal model for saithe and log-normal model for trout. The study shows how catches change with different mesh sizes and mesh types of gillnets and it shows how selective gillnets are. A study like this can serve as a tool for choosing the right mesh size to avoid juvenile fish as well as to maximize and control catches of the targeted fish by the right choice of gillnets.

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