| Summary: | 碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 92 === In northeastern of Taiwan, Siganus canaliculatus is one of the most important target species for coastal gillnet fisheries. In order to realize the mesh selectivity of gillnet for Siganus canaliculatus, a field fishing experiment was conducted from 2003 to 2004, the fishing season of target species, in Aodi coastal area, Gongliao Township, Taipei County. To provide comparative data, an experiment has also been conducted in an indoor water tank containing a group of Siganus canaliculatus of known number and body size. The mesh sizes 7.3, 7.5, 8.8, 10 and 10.2cm (stretched-mesh size) of gillnets as well as 10.1cm of inner net of trammel net were adopted in the field fishing experiment. The mesh sizes 2.2, 2.8 and 3.4cm were adopted in the indoor water tank experiment.
Selectivity was assessed by Kitahara’s method based on the measurement of fork length and maximum body girth. Because of the different maximum body girth, the results of selectivity curve in terms of fork length ratio to mesh length (L/M), determined from the field fishing experiment and the indoor water tank experiment, are different. The results of selectivity curve in terms of girth ratio to mesh perimeter (G/P) between two experiments are the same. From the results of the two experiments, an optimum mesh size of 9.1cm was determined for Siganus canaliculatus in the fishing season.
Keywords: Gillnet, Mesh selectivity, Siganus canaliculatus
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