DUML surveys for the stock discrimination of bottlenose dolphins along the Outer Banks of North Carolina 2011-2012

Original provider: Duke University Marine Laboratory Dataset credits: Duke University Marine Laboratory Abstract: Four stocks of bottlenose dolphins (<i>Tursiops truncatus</i>) have been described in the waters of North Carolina: the Northern Migratory (NM); Southern Migratory (SM); Northern NC Estuarine System (NNCES); and Southern NC Estuarine System (SNCES) stocks (Waring et al. 2013). The two migratory stocks occur in coastal shelf waters, but dolphins from the two estuarine stocks also occur in near-shore coastal waters. During summer, dolphins from both the SM and NNCES stocks are vulnerable to by-catch in small-mesh gill nets set in coastal waters, primarily gill nets set for Spanish mackerel very close to shore along the Outer Banks. Little is currently known about the degree of overlap of dolphins from these two stocks along the Outer Banks, which hampers our ability to assess the true impact of these by-catches. In this research project we photographed and collected biopsy samples of bottlenose dolphins from both the SM and NNCES stocks in coastal waters along the Outer Banks during the summer and early autumn of 2011 and 2012. We sampled dolphins from both stocks to determine: (1) their distribution patterns; (2) the degree of overlap between NNCES and SM stocks; and (3) specifically, how far from shore the NNCES animals are found. Almost all of the groups we encountered were from the SM stock; we only encountered four groups of NNCES dolphins during these surveys. In general, estuarine animals were observed in relatively small groups, close to shore, in shallow water and in relatively close proximity to an inlet. Sighting and biopsy locations were significantly closer to shore (p=0.00278 and p=0.00091, respectively) and shallower (p=0.00117) for the NNCES stock than the SM stock. We note, however, that these conclusions should be tempered by the small sample of estuarine animals we observed. Nevertheless, all four sightings of estuarine dolphins occurred within 500-m of shore and in waters less than 4-m deep. The distribution of the two stocks overlapped in waters very close to shore, but we did not observe any estuarine groups beyond 500 m. from shore.<br><br> This work was funded by the North Carolina Sea Grant Bycatch Reduction Marine Mammal Project. This research was conducted under General Authorization Number 16185 from the NMFS held by Dr. Andrew Read, allowing the close approach to bottlenose dolphins for research purposes.<br><br> Reference: <a href="http://www.nmfs.noaa.gov/pr/sars/pdf/ao2012.pdf">Waring G.T., E. Josephson, K. Maze-Foley and P.E. Rosel (eds.) 2013. U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments – 2012.</a> Accessed 28 September 2013.原始提供方：杜克大学海洋实验室（Duke University Marine Laboratory） 数据集贡献方：杜克大学海洋实验室（Duke University Marine Laboratory） 摘要： 北卡罗来纳州海域已记录4种宽吻海豚（*Tursiops truncatus*）种群，分别为北方洄游种群（Northern Migratory, NM）、南方洄游种群（Southern Migratory, SM）、北卡罗来纳州北部河口系统种群（Northern NC Estuarine System, NNCES）以及北卡罗来纳州南部河口系统种群（Southern NC Estuarine System, SNCES）（Waring等，2013）。两种洄游种群栖息于大陆架近海水域，而两种河口种群的宽吻海豚也会出现在近岸沿海海域。夏季期间，南方洄游种群（SM）与北卡罗来纳州北部河口系统种群（NNCES）的宽吻海豚均易在近岸海域的小型刺网中被副渔获，这类刺网主要为沿外岸群岛近岸区域布设、用于捕捞西班牙鲭的刺网。目前学界对这两种群在外岸群岛的分布重叠程度尚不清楚，这阻碍了我们准确评估此类副渔获事件实际影响的能力。 本研究于2011年与2012年的夏季及早秋时节，在外岸群岛近海水域对南方洄游种群（SM）与北卡罗来纳州北部河口系统种群（NNCES）的宽吻海豚进行了摄影采样，并收集了其皮肤活检样本。本研究对两种群的海豚进行采样，旨在明确三个研究目标：（1）其分布模式；（2）北卡河口系统种群（NNCES）与南方洄游种群（SM）的分布重叠程度；（3）具体而言，北卡河口系统种群的海豚活动距离岸线的最远距离。 本研究中记录到的海豚群几乎全部属于南方洄游种群（SM），本次调查仅记录到4群北卡河口系统种群（NNCES）的宽吻海豚。总体而言，河口种群的海豚多以较小的群体活动，栖息于近岸浅水环境，且相对靠近入海口。与南方洄游种群（SM）相比，北卡河口系统种群（NNCES）的目击位置与活检采样位置均显著更靠近岸线（分别对应p=0.00278与p=0.00091），且采样水域深度更浅（p=0.00117）。但需指出，本研究观测到的河口种群样本量较小，因此上述结论需谨慎解读。尽管如此，本次记录到的4群河口宽吻海豚均出现在距离岸线500米以内、水深不足4米的水域中。两种群的分布在极近岸水域存在重叠，但未观测到河口种群的海豚群出现在距离岸线500米以外的区域。 本研究受北卡罗来纳州海洋拨款副渔获减少海洋哺乳动物项目资助。本研究的开展遵循了由安德鲁·里德（Andrew Read）博士持有、美国国家海洋渔业局（National Marine Fisheries Service, NMFS）签发的第16185号通用授权许可，该许可允许为科研目的近距离接触宽吻海豚。 参考文献：Waring G.T.、Josephson E.、Maze-Foley K.与Rosel P.E.（编辑），2013年。《美国大西洋及墨西哥湾海洋哺乳动物种群评估——2012》。于2013年9月28日访问。