Worldwide, cetaceans are impacted by human activities, and those populations that occur in shallow-nearshore habitats are particularly vulnerable. We present the results of the first long-term study on the responses of a coastal population of endangered Irrawaddy dolphins to widespread habitat changes. We particularly investigated their responses in terms of distribution and abundance. Boat-based, line-transect surveys were conducted during 12 discrete survey periods in 7 survey years spanning a 15-year period (totaling 78 days and 4,630 km of effort) in Balikpapan Bay, East Kalimantan, Indonesia. Irrawaddy dolphins were sighted on 136 occasions. Through DISTANCE analysis, a decrease in population density in the inner Bay area was observed from 0.45 dolphins/km2 in 2000–2001 (CV = 24%) to 0.34 and 0.32 dolphins/km2 in 2008 and 2015 (CV = 31% and 25%). A shift in distribution was noted between the periods 2000–2002 and 2008–2015 with significantly lower occurrence in the lower Bay segment compared to upper Bay segments. No sightings were made in the outer Bay area in later years, which coincided with increased shipping traffic in these areas. A peak in stranding events in 2016 and 2018 followed extremely high phenol levels within Bay waters in 2015 and a large-scale oil spill in 2018. The mean annual mortality rates of 0.67 Irrawaddy dolphins/year is unsustainable based on the lower potential biological removal (PBR) values for best abundance estimates of 2015 (Ndistance = 45 and Nmark–recapture = 73). Other threats to local dolphins include unsustainable fishing, underwater noise caused by construction, particularly piling activities. The research helped to identify Balikpapan Bay as an Important Marine Mammal Area by the IUCN MMPA Taskforce. Serious concerns remain for the concrete plans to move Indonesia’s capital city to the area north of the Bay, in terms of increased shipping traffic and harbor construction in the upper Bay segments that represent primary dolphin habitat. We recommend that protected areas be assigned for marine mammals and artisanal fisheries and shipping traffic and piling activities be excluded from these areas. We also recommend a legislated requirement of a mitigation protocol compulsory for piling and seismic activities within Indonesia.

中文翻译：

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印度尼西亚巴厘巴板湾濒危伊洛瓦底江海豚种群的长期种群和分布动态响应沿海开发

在世界范围内，鲸类动物受到人类活动的影响，而那些生活在近岸浅水栖息地的鲸类种群尤其脆弱。我们展示了关于濒临灭绝的伊洛瓦底江海豚沿海种群对广泛栖息地变化的反应的首次长期研究的结果。我们特别研究了他们在分布和丰度方面的反应。在印度尼西亚东加里曼丹的巴厘巴板湾进行了跨越 15 年的 7 个调查年的 12 个离散调查期间（总共 78 天和 4,630 公里的努力），以船为基础的线样调查。伊洛瓦底江海豚出现了 136 次。通过距离分析，观察到内湾区的人口密度从 2000-2001 年的 0.45 只海豚/平方公里（CV = 24%）下降到 0.34 和 0。2008 年和 2015 年为 32 只海豚/平方公里（CV = 31% 和 25%）。在 2000-2002 年和 2008-2015 年期间注意到分布的变化，与上湾段相比，下湾段的发生率显着降低。后来几年外湾地区没有出现任何目击事件，这与这些地区的航运量增加相吻合。2016 年和 2018 年搁浅事件的高峰发生在 2015 年海湾水域中苯酚含量极高以及 2018 年发生大规模石油泄漏之后。 基于较低的潜在生物清除率，每年 0.67 只伊洛瓦底江海豚的平均死亡率是不可持续的（ PBR) 2015 年最佳丰度估计值（Ndistance = 45 和 Nmark-recapture = 73）。当地海豚面临的其他威胁包括不可持续的捕捞、建筑引起的水下噪音，尤其是打桩活动。该研究有助于 IUCN MMPA 工作组将巴厘巴板湾确定为重要的海洋哺乳动物区。将印度尼西亚首都迁往海湾以北地区的具体计划仍然令人严重担忧，因为在代表主要海豚栖息地的上海湾部分增加了航运量和港口建设。我们建议为海洋哺乳动物和手工渔业指定保护区，并将航运和打桩活动排除在这些区域之外。我们还建议对印度尼西亚境内的打桩和地震活动强制实施缓解协议的立法要求。在代表主要海豚栖息地的上湾段增加航运量和港口建设。我们建议为海洋哺乳动物和手工渔业指定保护区，并将航运和打桩活动排除在这些区域之外。我们还建议对印度尼西亚境内的打桩和地震活动强制实施缓解协议的立法要求。在代表主要海豚栖息地的上湾段增加航运量和港口建设。我们建议为海洋哺乳动物和手工渔业指定保护区，并将航运和打桩活动排除在这些区域之外。我们还建议对印度尼西亚境内的打桩和地震活动强制实施缓解协议的立法要求。