Efficacy of 2 common bait types in reducing bycatch of coastal sharks on bottom longline gear in the absence of choice Fishery Bulletin

A recent study determined that when simultaneously exposed to 2 different commonly used baits, certain shark species demonstrate preferences for a specific bait on bottom longlines. To further investigate the value of bait type to reduce shark bycatch, we conducted single-bait-type bottom longline sets with standardized gear baited with either mackerel or squid. For 4 of the 5 shark species captured, there was no significant difference in catch rates with bait type. However, catch rates of Atlantic sharpnose sharks (Rhizoprionodon terraenovae) were significantly higher on mackerel-baited hooks. Our results indicate that the use of squid as bait can reduce the catch of at least one shark species in the northern Gulf of Mexico while not reducing the catch of a targeted species, in this case, the red snapper (Lutjanus campechanus). However, because some protected species, most notably sea turtles, have been shown to have higher catch rates on squid-baited hooks, it is necessary to assess the effect of a specific bait across all taxa directly or indirectly affected by a particular gear type before adopting any bycatch reduction measure.

近期一项研究证实，当同时接触两种常用钓饵时，部分鲨鱼物种在底层延绳钓作业中会表现出对特定钓饵的偏好。为进一步探究钓饵类型在减少鲨鱼兼捕方面的应用价值，我们采用标准化钓具开展了单一钓饵类型的底层延绳钓作业，钓具分别以鲭鱼或鱿鱼作为钓饵。在捕获的5种鲨鱼中，有4种的捕获率在不同钓饵类型下无显著差异。不过，大西洋尖吻鲨（Rhizoprionodon terraenovae）在鲭鱼钓饵钩上的捕获率显著更高。本研究结果表明，在墨西哥湾北部海域，使用鱿鱼作为钓饵可减少至少一种鲨鱼物种的捕获量，同时不会降低目标捕捞物种——红鳍笛鲷（Lutjanus campechanus）的捕获量。但鉴于已有研究显示部分保护物种（最典型的为海龟）在鱿鱼钓饵钩上的捕获率更高，因此在采用任何兼捕减少措施前，有必要针对某类钓具所直接或间接影响的所有生物类群，评估特定钓饵的综合影响效果。