ABSTRACT: Protective legislation and management have led to an increase in California’s sea otter Enhydra lutris nereis population. While sea otter recovery has been linked to ecosystem benefits, sea otter predation may negatively affect commercially valuable species. Understanding the potential influence of sea otters is of particular importance as their range expands into estuaries that function as nurseries for commercially valuable species like Dungeness crab Metacarcinus magister. We consider how sea otter predation has affected the abundance and size of juvenile Dungeness crab in Elkhorn Slough, California, USA, and analyzed cancrid crab abundance and size across 4 California estuaries with and without sea otters to understand how biotic and abiotic factors contribute to observed variation in crab size and abundance. We compared trends in southern sea otters relative to Dungeness crab landings in California to assess whether increasing sea otter abundance have negatively impacted landings. In Elkhorn Slough, juvenile Dungeness crab abundance and size have declined since 2012, coinciding with sea otter population growth. However, the impact of sea otters on juvenile Dungeness crab size was habitat-specific and only significant in unvegetated habitat. Across estuaries, we found that cancrid crab abundance and size were negatively associated with sea otter presence. While abiotic factors varied among estuaries, these factors explained little of the observed variation in crab abundance or size. Although we found evidence that sea otters can have localized effects on cancrid crab populations within estuaries, we found no evidence that southern sea otters, at recent population sizes, have negatively impacted Dungeness crab landings in California from 2000-2014.

中文翻译：

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表征回收海獭对加利福尼亚河口具有重要商业意义的螃蟹的影响

摘要：保护性立法和管理导致加利福尼亚海獭Enhydra lutris nereis种群增加。尽管海獭的恢复与生态系统的利益相关，但海獭的捕食可能会对商业上有价值的物种产生负面影响。了解海獭的潜在影响尤为重要，因为它们的范围会扩展到河口，充当诸如珍宝蟹Metacarcinus magister等具有商业价值的物种的育苗场。我们考虑了海獭的捕食如何影响美国加利福尼亚州埃尔克霍恩斯劳的幼体大白蟹的数量和大小，并分析了有水獭和无水獭的情况下，加利福尼亚州4个河口的蟹类物种的丰度和大小，以了解所观察到的生物和非生物因素螃蟹大小和丰度的变化。我们比较了南部水獭相对于加利福尼亚州太平洋大蟹登陆的趋势，以评估海獭数量的增加是否对登陆产生了负面影响。自2012年以来，在埃尔克霍恩斯劳（Elkhorn Slough），少年大吉尼斯（Dungeness）螃蟹的数量和大小都在下降，这与海獭数量的增长相吻合。然而，水獭对太平洋大螯蟹幼体大小的影响是特定于栖息地的，并且仅在无植被的栖息地中才有意义。在整个河口，我们发现，蟹的丰度和大小与海獭的存在呈负相关。尽管河口中的非生物因素有所不同，但这些因素几乎不能解释所观察到的蟹的丰度或大小的变化。尽管我们发现有证据表明海獭会对河口内的螃蟹种群产生局部影响，但我们没有发现证据表明在最近的种群规模下，南部海獭在2000-2014年间对加利福尼亚的Dungeness螃蟹着陆产生了负面影响。