ABSTRACT

This paper describes the impact of dredging on populations of the wedge clam (Donax trunculus) at two sites along the northern Alboran coast. Damage was assessed by quantifying shell and foot damage on commercial clams caught with mechanical dredges. Survival experiments were carried out to assess their survival capacity after 24 h purification treatment and 72 h cold storage, which represents an issue of great interest for fisheries research, management and marketing. Overall, 2.4% of wedge clams suffered any type of damage, including chipped edges and scratched valves. Higher proportions of shell-damaged individuals were positively correlated to bottom features (e.g. gravel content in sediment). Moreover, higher towing speed significantly increased shell damage. Analyses of shell damage areas revealed that the anterior dorsal and ventral parts of the shell are the most vulnerable to dredging. A total of 15.9% of individuals showed damage on the foot, which seems not to affect their survival. The incidence of foot damage was mostly linked to sublethal predation, reflected in a positive correlation between the proportion of foot-damaged individuals and biomass of decapod crustaceans in the fishing ground. Finally, D. trunculus exhibited very low mortality rates after 24 h purification treatment (0.2–0.4%) and 72 h cold storage (0.3–3.2%). The survival rate at the end of the experiment was high (>96%), with the highest mortality observed 96 h after the fishing day. No correlations were found between mortality rates and bottom type or towing speed.

摘要

本文描述了疏浚对楔形蛤（Donax trunculus ）种群的影响) 在奥尔博兰北部海岸的两个地点。通过量化用机械挖泥机捕获的商业蛤蜊的壳和脚损坏来评估损坏情况。进行了成活实验以评估它们经过 24 小时净化处理和 72 小时冷藏后的成活能力，这是渔业研究、管理和营销非常感兴趣的问题。总体而言，2.4% 的楔形蛤受到任何类型的损坏，包括边缘缺口和阀门划伤。较高比例的贝壳受损个体与底部特征（例如沉积物中的砾石含量）呈正相关。此外，更高的拖曳速度显着增加了炮弹损坏。对贝壳损伤区域的分析表明，贝壳的前背侧和腹侧部分最容易受到疏浚。一共15个。9% 的人脚部有损伤，这似乎不影响他们的生存。足部损伤的发生率主要与亚致死捕食有关，反映在足部损伤个体的比例与渔场十足目甲壳类动物的生物量之间呈正相关。最后，D. trunculus在 24 小时净化处理 (0.2-0.4%) 和 72 小时冷藏 (0.3-3.2%) 后表现出非常低的死亡率。实验结束时的成活率很高（> 96%），在捕鱼日后 96 小时观察到的死亡率最高。死亡率与船底类型或拖曳速度之间没有发现相关性。