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Modelling the contact probability and size-selectivity of toothed dredges
Authors:Takahisa?Mituhasi  Toshihide?Kitakado  Fuxiang?Hu  Email author" target="_blank">Tadashi?TokaiEmail author
Institution:Faculty of Marine Science, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
Abstract:ABSTRACT:   To estimate fishing gear selectivity of clam dredges from data of paired-gear tests in the SELECT analysis process, this paper presents a statistical model of the probability of a clam coming into contact with the dredge teeth and size-selectivity of the control gear. The net-mouth available selectivity is defined as the product of the probability of a clam contacting the dredge teeth and size-selectivity induced by tooth spacing. The model based on the SELECT analysis was tested by using data generated by virtual paired-gear test in which the control dredge of the smallest tooth spacing is assumed to be size-selective. No clear difference in shell length distribution between dredges of different tooth spacings was found in the simulation when the contact probability was small. The plots of proportion of clams caught in the test dredge to the total catch number of clams were U-shaped, and the model fitted the data well. For each simulation consisting of 500 replications, the sample mean and mean square error of each parameter were obtained to evaluate the performance of estimation by comparing with the true value. Parameters were properly estimated with the model.
Keywords:available selection  clam  contact probability  contact selection  dredge  fishing gear selectivity
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