Intensive commercial harvesting of the wedge clam Donax trunculus and the striped venus Chamelea gallina was conducted along the southern coast of the Marmara Sea using a mechanical dredge (MD) and a hand dredge (HD). The purpose of this study was to characterize and quantify the bycatch and discards of both types of dredge. The dredge tows were performed along sandy bottoms at depths ranging from 0 to 2 m between August 2011 and July 2012. A total of 29 species belonging to 20 families were collected from 137 tows during 67 fishing trips. The total catch in terms of biomass was 107,752.69 g for the MD and 94,257.40 g for the HD, of which 10.78% and 5.08%, respectively, comprised commercial bycatch species, discards, individuals of the target species smaller than the minimum legal size (< MLS), and mortality. Besides the target species (D. trunculus and C. gallina), 27 other species were caught as bycatch and partially discarded. The predominant commercially valuable species in the bycatch were Ruditapes philippinarum (0.94%) and Mytilus galloprovincialis (0.48%) for the HD, and Acanthocardia tuberculata (0.34%) and Rapana venosa (0.34%) for the MD. The rate in weight of discards including < MLS and mortality were 9.22% for the MD and 2.82% for the HD. The gastropods Cerithium vulgatum (58.28%) and Tritia neritea (13.80%) and the crustacean Liocarcinus depurator (5.57%) comprised 77.65% of the discards in weight. Overall, a lower commercial bycatch species + discards + < MLS + mortality rate in terms of weight (5.08%) was observed for the HD compared to the MD (10.78%). The findings of this study are important for the development of policies for the conservation and sustainable fishing of bivalves.

中文翻译：

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土耳其马尔马拉海南部海岸使用的两种双壳类挖泥船的副渔获物和丢弃物，目标是竹芋和 Chamelea gallina

使用机械挖泥机 (MD) 和手动挖泥机 (HD) 在马尔马拉海南部海岸对楔形蛤 Donax trunculus 和条纹金星 Chamelea gallina 进行了密集的商业捕捞。本研究的目的是表征和量化两种类型疏浚物的兼捕和丢弃物。2011 年 8 月至 2012 年 7 月，在 0 至 2 m 深度的沙底进行了疏浚拖曳。在 67 次捕鱼之旅中，从 137 条拖曳中收集了 20 科 29 种物种。就生物量而言，MD 的总产量为 107,752.69 克，HD 的总产量为 94,257.40 克，其中分别占 10.78% 和 5.08% 的商业兼捕物种、丢弃物、目标物种的个体小于法定最小尺寸（< MLS）和死亡率。除了目标物种（D. trunculus 和 C. gallina)，其他 27 个物种被作为副渔获物捕获并部分丢弃。副渔获物中主要的商业价值物种是 HD 的菲律宾蛤蜊 (0.94%) 和 Mytilus galloprovincialis (0.48%)，以及 MD 的 Acanthocardia tuberculata (0.34%) 和 Rapana venosa (0.34%)。包括 < MLS 和死亡率在内的丢弃物重量比率，MD 为 9.22%，HD 为 2.82%。腹足动物 Cerithium v​​ulgatum (58.28%) 和 Tritia neritea (13.80%) 和甲壳类 Lioccarcinus depurator (5.57%) 占丢弃物重量的 77.65%。总体而言，与 MD (10.78%) 相比，HD 观察到的商业兼捕物种 + 丢弃物 + < MLS + 重量死亡率 (5.08%) 较低。