Reading: Multi-mesh gillnet selectivity of Oreochromis mossambicus and O. niloticus (Cichlidae) in th...

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Multi-mesh gillnet selectivity of Oreochromis mossambicus and O. niloticus (Cichlidae) in the fishery of three large perennial reservoirs in Sri Lanka

Authors:

R. P. Prabath K. Jayasinghe,

University of Kelaniya, Kelaniya 11600, LK
About R. P. Prabath K.

Department of Zoology and Environmental Management

 

Marine Biological Resources Division, National Aquatic Resources Research and Development Agency, Crow Island, Colombo 15

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Upali S. Amarasinghe ,

University of Kelaniya, Kelaniya 11600, LK
About Upali S.

Department of Zoology and Environmental Management

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Jacques Moreau

Ecole Nationale Supérieure Agronomique de Toulouse (ENSAT), P.O. Box 107 Auzeville Tolosane, 31326 Castanet Tolosan Cédex, FR
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Abstract

As in many tropical reservoir fisheries, the major fishing gear in the reservoirs of Sri Lanka is gillnet. Gillnets of a wide range of stretched mesh sizes (6.9 - 11.4 cm) are used in individual boats in Sri Lankan reservoirs targeting mainly two exotic cichlid species, Oreochromis mossambicus and O. niloticus, which dominate the fisheries accounting for over 80% of the landings. Although the filament characteristics and dimensions of gillnets of different mesh sizes are uniform, their mesh composition varies from boat to boat making catch samples in individual boats are under the influence of different selectivity patterns. As such, an approach is presented for constructing the overall selection curves in the sampled boats during different sampling occasions for the two cichlid fish species in the three reservoirs. For this purpose, gillnet selectivity of each mesh size was determined using Baranov-Holt method. Probabilities of capture of mesh-wise gillnet selection curves were then summed up giving weight to the contribution of each mesh size to the total number of net pieces in the sampled boat, to determine the overall gillnet selection from gillnets of all mesh sizes. The importance of the findings of the present study for length-based stock assessment methods and for imposing mesh regulations to the gillnet fisheries in reservoirs of Sri Lanka is discussed.

DOI: http://doi.org/10.4038/sljas.v22i1.7517
How to Cite: Jayasinghe, R.P.P.K., Amarasinghe, U.S. & Moreau, J., (2017). Multi-mesh gillnet selectivity of Oreochromis mossambicus and O. niloticus (Cichlidae) in the fishery of three large perennial reservoirs in Sri Lanka. Sri Lanka Journal of Aquatic Sciences. 22(1), pp.55–66. DOI: http://doi.org/10.4038/sljas.v22i1.7517
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Published on 01 Mar 2017.
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