Secondary predation constrains DNA-based diet reconstruction in two threatened shark species

Increasing fishing effort, including bycatch and discard practices, are impacting marine biodiversity, particularly among slow-to-reproduce taxa such as elasmobranchs, and specifically sharks. While some fisheries involving sharks are sustainably managed, collateral mortalities continue, contributing towards > 35% of species being threatened with extinction. To effectively manage shark stocks, life-history information, including resource use and feeding ecologies is pivotal, especially among those species with wide-ranging distributions. Two cosmopolitan sharks bycaught off eastern Australia are the common blacktip shark (Carcharhinus limbatus; globally classified as Near Threatened) and great hammerhead (Sphyrna mokarran; Critically Endangered). We opportunistically sampled the digestive tracts of these two species (and also any whole prey; termed the ‘Russian-doll’ approach), caught in bather-protection gillnets off northern New South Wales, to investigate the capacity for DNA meta...

不断加剧的捕捞活动，包括兼捕渔获（bycatch）与渔获丢弃（discard）行为，正严重冲击海洋生物多样性，尤其对繁殖缓慢的分类群（taxa）如板鳃亚纲动物（elasmobranchs），乃至鲨鱼类群的影响更为显著。尽管部分鲨鱼捕捞渔业已实现可持续管理，但兼捕引发的附带死亡仍持续存在，导致超过35%的鲨鱼物种面临灭绝威胁。若要有效管理鲨鱼种群资源，其生活史信息（life-history information）——包括资源利用模式与摄食生态（feeding ecologies）——至关重要，对于分布范围广泛的物种而言更是如此。在澳大利亚东部海域被兼捕的两种广布鲨鱼分别为黑边鳍真鲨（*Carcharhinus limbatus*，全球评估等级为近危（Near Threatened））与无沟双髻鲨（*Sphyrna mokarran*，极危（Critically Endangered））。我们对在新南威尔士州北部海域防泳客刺网（bather-protection gillnets）中捕获的这两种鲨鱼的消化道，以及其体内的完整猎物进行了偶遇采样，该采样策略被称为“套娃法（Russian-doll approach）”，以探究DNA元（DNA meta...）的相关研究潜力。