Kyoto Institute of Oceanic and Fishery Science, Kyoto 626-0052, Japan
This paper presents the mesh selectivity for willowy flounder Tanakius kitaharai using a beam trawl net with experimental bags of three different mesh opening: 35.8mm, 42.9mm and 49.4mm. Forty seven hauls of beam trawl towing were carried out in the area between 100 and 180m in depth off Kyoto Prefecture from August 1999 to August 2000. The parameters of logistic and Richards equations for mesh selectivity curves in each mesh opening were estimated by the maximum likelihood method. The Richards equation model was selected as the better-fit model because it had a smaller value of AIC than the logistic equation model. The values of 50% selection length of 35.8mm, 42.9mm and 49.4mm sizes were estimated to be 97.0mm, 112.4mm and 129.6mm, respectively. On the other hand, many juveniles of willowy flounder were clearly caught by commercial fishery with cod-end of 20.9mm mesh opening. This paper also discusses the effectiveness of mesh enlargement for protecting juvenile flounders based on mesh selectivity estimated in this study.