Effect of tooth spacing on the contact selection and available selection of a dredge for the equilateral Venus clam <Emphasis Type="Italic">Gomphina melanaegis</Emphasis> |
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| Authors: | In-Ok?Kim Takahisa?Mituhasi Tae-Hyun?Jo Chang-Doo?Park Email author" target="_blank">Tadashi?TokaiEmail author |
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| Institution: | National Fisheries Research and Development Institute, Gijang-gun, Busan 619-902, Korea and;Faculty of Marine Science, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan |
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| Abstract: | ABSTRACT: The effect of various tooth spacing on the contact selection and the net-mouth available selection of a dredge for the equilateral Venus clam Gomphina melanaegis is evaluated by applying a contact-probability model based on the SELECT method to the data of paired-gear tests with a control dredge of 12-mm tooth spacing and four test dredges of tooth spacing 16, 20, 24 and 35 mm. A master selection curve was estimated to be s ( R ) = exp(−11.23 R + 4.799)/(1 + exp−11.23 R + 4.799]) where, R is l / d , the ratio of the shell length, l , to the tooth spacing, d . The shell width of 50% retention was slightly smaller than the tooth spacing, which means that size selectivity of teeth was a type of contact selection which was dependent on the tooth spacing. Contact probability, δ, of the clams coming into contact with the teeth were 0.625, 0.467, 0.563, 0.670 and 0.976 for tooth spacing 12, 16, 20, 24 and 35 mm, respectively. This indicates that some clams entered the dredge bagnet without contacting the teeth as the sand clogging the tooth spacing carried them into the bagnet. Available selection curve of the dredge net-mouth with teeth was obtained as δ s ( R ) + 1 − δ , and examined in terms of the legal landing size of the Venus clam. |
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| Keywords: | available selection contact selection dredge equilateral Venus clam fishing gear selectivity Gomphina melanaegis tooth spacing |
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