The Greenland shark (Somniosus microcephalus) is the main bycatch species in established and exploratory inshore longline fisheries for Greenland halibut (Reinhardtius hippoglossoides) on the east coast of Baffin Island, Canada. Bycatch and entanglement in longline gear has at times been substantial and post-release survival is questionable when Greenland sharks are released with trailing fishing gear. This study investigated the effect of the type of fishing line used in the gangion and gangion breaking strength on catch rates of Greenland shark and Greenland halibut in bottom set longlines. Circle (size 14/0, 0° offset) hooks were used throughout the study. Behavior of captured sharks, mode of capture (i.e., jaw hook and/or entanglement), level of entanglement in longline gear, time required to disentangle sharks and biological information (sex, body length and health status) were recorded. Catch rates of Greenland shark were independent of monofilament nylon gangion breaking strength and monofilament gangions captured significantly fewer Greenland sharks than the traditional braided multifilament nylon gangion. Catch rates and body size of Greenland halibut did not differ significantly between gangion treatments. Although most (84%) of the Greenland sharks were hooked by the jaw, a high percentage (76%) were entangled in the mainline. The mean length of mainline entangled around the body and/or caudal peduncle and caudal fin was 28.7 m. Greenland sharks exhibited cannibalistic behavior with 15% of captured sharks cannibalized. All remaining sharks were alive and survived the disentanglement process which can be attributed to their lethargic behavior and lack of resistance when hauled to the surface. Thus, as a conservation measure fishers should be encouraged to remove trailing fishing gear prior to release. Our results are used to demonstrate benefits to the fishing industry with regard to an overall reduction in the period of time to disentangle sharks and damage to fishing gear by switching from braided multifilament to monofilament gangions in Greenland halibut longline fisheries.

中文翻译：

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单丝尼龙与编织复丝尼龙节对底部延绳钓格陵兰鲨鱼（Somniosus microcephalus）捕获率的影响

格陵兰鲨（Somniosus microcephalus）是加拿大巴芬岛东海岸格陵兰大比目鱼（Reinhardtius hippoglossoides）已建立和探索性近海延绳钓渔业的主要兼捕物种。延绳钓渔具的误捕和缠结有时很严重，当格陵兰鲨鱼用拖尾渔具放生时，放生后的生存是有问题的。本研究调查了钓组中使用的钓线类型和钓组断裂强度对底部延绳钓格陵兰鲨鱼和格陵兰大比目鱼捕获率的影响。在整个研究过程中使用了圆形（尺寸 14/0，0° 偏移）挂钩。捕获鲨鱼的行为、捕获方式（即颚钩和/或缠结）、延绳钓渔具的缠结程度、解开鲨鱼和生物信息所需的时间（性别、体长和健康状况）进行记录。格陵兰鲨鱼的捕获率与单丝尼龙节断裂强度无关，与传统编织复丝尼龙节相比，单丝节捕获的格陵兰鲨鱼明显更少。格陵兰大比目鱼的捕获率和体型在神经节处理之间没有显着差异。尽管大部分 (84%) 格陵兰鲨鱼被下颚钩住，但仍有很大比例 (76%) 被主线缠住。缠绕在身体和/或尾柄和尾鳍周围的主线平均长度为28.7 m。格陵兰鲨鱼表现出自相残杀行为，15% 的捕获鲨鱼被自相残杀。所有剩下的鲨鱼都活着并在解开过程中幸存下来，这可归因于它们在被拖到水面时昏昏欲睡的行为和缺乏抵抗力。因此，作为一项保护措施，应鼓励渔民在放生前移除拖尾渔具。我们的结果用于证明通过在格陵兰比目鱼延绳钓渔业中从编织复丝到单丝团，总体上减少解开鲨鱼的时间和对渔具的损害对渔业的好处。