Estimating harbour seal abundance and status in an estuarine habitat in north-east Scotland
Estimating harbour seal abundance and status in an estuarine habitat in north-east Scotland
复制标题
估计苏格兰东北部河口栖息地的斑海豹数量和状况
DOI：
10.2307/2404846
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发表时间：
1997
影响因子：
5.7
通讯作者：
Ann Mackay
中科院分区：
文献类型：
--
作者：
Paul M. Thompson;D. Tollit;David J. A. Wood;H. M. Corpe;Philip S. Hammond;Ann Mackay
1.斑海豹是分布最广的鳍足动物物种，它们上岸到各种不同的栖息地休息、换羽和繁殖。对它们的丰度和地位的估计取决于陆上迁徙群体中的动物数量，但目前尚不清楚目前的技术在多大程度上适合所有栖息地。2.这项研究旨在确定估计苏格兰东北部河口栖息地海豹数量和状况的最合适方法。定期进行退潮计数，以确定年度计数的最佳时间。然后，将1993年的调查数据与关于海豹活动的遥测数据结合起来，估计海豹的丰度。最后，使用一年内计数变异性的数据进行模拟，以确定这些技术在检测丰度趋势方面的能力。3.结果表明，在幼崽季节(6月中旬至7月中旬)进行的年度计数对该栖息地的丰度提供了最好的估计。这些结果与岩石岸边栖息地的研究结果形成了对比，在8月换羽期间进行的计数提供了更可靠的丰度估计。4.1993年，在6月15日至7月15日期间，平均有1007只海豹在退潮时被打捞上来。男性(低潮0.521)和女性(0.698)的拖带频率有显着差异，但在此期间没有发现性别差异。将遥测数据与马里湾的计数结果结合起来，得出的丰度估计为1653(95%的可信区间为1471-1836)。5.在确定用于趋势分析的适当丰度指数方面，讨论了年内和年间拖带行为变化的潜在影响。鉴于捕捞群体的性别结构可能出现季节性变化，我们建议监测海豹数量趋势的方案应在年度周期中的两个不同时间点进行年度计数。
1. Harbour seals are the most widespread of pinniped species, coming ashore onto a variety of different habitats to rest, moult and breed. Estimates of their abundance and status rely on counts of animals in terrestrial haul-out groups but it is not clear to what extent current techniques are appropriate for all habitats. 2. This study aimed to determine the most appropriate methods for estimating the abundance and status of harbour seals in an estuarine habitat in north-east Scotland. Regular low-tide counts were conducted to identify the best time for annual counts. Survey data for 1993 were then combined with telemetry data on seal activity to produce an estimate of abundance. Finally, simulations using data on the variability of counts within a single year were used to determine the power of these techniques to detect trends in abundance. 3. The results suggest that annual counts conducted during the pupping season (mid-June to mid-July) provide the best estimates of abundance in this habitat. These results contrast with those from studies in rocky-shore habitats where counts made during the August moult provided more reliable abundance estimates. 4. In 1993, an average of 1007 seals were hauled out at low tides during the period 15 June-15 July. There were significant differences in haul-out frequency for males (0.521 of low tides) and females (0.698 of low tides) but no within-sex variation was detected during this period. Combining the telemetry data with the results of counts from the Moray Firth produced an abundance estimate of 1653 (95% confidence limits 1471-1836). 5. The potential effects of within and between-year variation in haul-out behaviour are discussed in relation to identifying suitable indices of abundance for trend analysis. In view of likely seasonal changes in the sex structure of haul-out groups, we recommend that programmes to monitor trends in harbour seal abundance should conduct annual counts at two different points in the annual cycle.