Wildlife Institute of India, Chandrabani, Dehradun, Uttarakhand, 248001, India.
Sci Rep. 2022 Jun 7;12(1):9382. doi: 10.1038/s41598-022-12670-y.
Ganges River dolphins echolocate, but this mechanism is inadequate for poor sonar-echoing objects such as the monofilament gillnets, causing considerable net entanglement related mortalities. Net entanglement related deaths are one of the major causes of cetacean population decline around the world. Experiments were carried out to understand the use of pingers-an acoustic deterrent, in aiding the deterrence of dolphins from fishing nets. Based on the dolphin clicks recorded, in an experimental setup spanning 36 days, a 90% deterrence was found; 22.87 ± 0.71 SE dolphin detection positive minutes per hour near non-pingered nets versus 2.20 ± 0.33 SE per hour near pingered net. Within 30 m radii of nets, visual encounters of non-calf reduced by 52% and calf by 9%, in the presence of pingers. No evidence of habituation to pingers, habitat avoidance in dolphins after pinger removal or a change in fish catch in nets because of pingers was found during the study. While the effectiveness of pingers on calves and fish catch needs further experimentation, the use of pingers to minimize net entanglement mortalities in the Ganges River dolphins seems to be the most promising solution currently available. These results have critical implications for the conservation of other species of river dolphins around the world.
恒河江豚会回声定位，但这种机制对于单丝刺网等回声效果差的物体不够有效，导致大量与网具缠绕相关的死亡。与网具缠绕相关的死亡是全球范围内鲸目动物数量下降的主要原因之一。本研究开展了实验，以了解声呐驱避器（一种声音驱避装置）在帮助海豚避开渔网方面的应用。根据在 36 天的实验设置中记录到的海豚咔哒声，发现 90%的海豚被驱离；在没有使用声呐驱避器的渔网附近，每小时海豚检测阳性时间为 22.87±0.71 SE，而在使用声呐驱避器的渔网附近，每小时海豚检测阳性时间为 2.20±0.33 SE。在离渔网 30 米半径范围内，有驱避器存在时，非幼豚的目击次数减少了 52%，幼豚减少了 9%。在研究过程中，没有发现海豚对声呐驱避器产生习惯、对栖息地产生回避，或由于声呐驱避器的存在导致渔网中的渔获量发生变化。虽然声呐驱避器对幼豚和渔获量的有效性还需要进一步的实验，但目前看来，使用声呐驱避器来最大限度地减少恒河江豚与网具缠绕相关的死亡率似乎是最有希望的解决方案。这些结果对保护世界各地其他种类的淡水豚具有重要意义。
