Institute of Aquaculture, University of Stirling, Stirling, Stirlingshire, United Kingdom.
PLoS One. 2012;7(9):e43560. doi: 10.1371/journal.pone.0043560. Epub 2012 Sep 6.
In Scotland and elsewhere, there are concerns that escaped farmed Atlantic salmon (Salmo salar L.) may impact on wild salmon stocks. Potential detrimental effects could arise through disease spread, competition, or inter-breeding. We investigated whether there is evidence of a direct effect of recorded salmon escape events on wild stocks in Scotland using anglers' counts of caught salmon (classified as wild or farmed) and sea trout (Salmo trutta L.). This tests specifically whether documented escape events can be associated with reduced or elevated escapes detected in the catch over a five-year time window, after accounting for overall variation between areas and years. Alternate model frameworks were somewhat inconsistent, however no robust association was found between documented escape events and higher proportion of farm-origin salmon in anglers' catch, nor with overall catch size. A weak positive correlation was found between local escapes and subsequent sea trout catch. This is in the opposite direction to what would be expected if salmon escapes negatively affected wild fish numbers. Our approach specifically investigated documented escape events, contrasting with earlier studies examining potentially wider effects of salmon farming on wild catch size. This approach is more conservative, but alleviates some potential sources of confounding, which are always of concern in observational studies. Successful analysis of anglers' reports of escaped farmed salmon requires high data quality, particularly since reports of farmed salmon are a relatively rare event in the Scottish data. Therefore, as part of our analysis, we reviewed studies of potential sensitivity and specificity of determination of farmed origin. Specificity estimates are generally high in the literature, making an analysis of the form we have performed feasible.
在苏格兰和其他地方，人们担心逃逸的养殖大西洋鲑（Salmo salar L.）可能会对野生鲑鱼种群产生影响。潜在的不利影响可能来自疾病传播、竞争或杂交。我们调查了苏格兰是否有记录的鲑鱼逃逸事件对野生种群产生直接影响的证据，方法是使用钓鱼者捕获的鲑鱼（分为野生或养殖）和海鳟（Salmo trutta L.）的数量。这专门测试了在五年的时间窗口内，是否可以将有记录的逃逸事件与捕获中检测到的减少或增加的逃逸事件联系起来，同时考虑了区域和年份之间的总体差异。替代的模型框架有些不一致，但是，在记录的逃逸事件与钓鱼者捕获的养殖起源鲑鱼比例较高之间，或者与总捕获量之间，没有发现强有力的关联。在当地逃逸和随后的海鳟捕获之间发现了微弱的正相关。这与如果鲑鱼逃逸对野生鱼类数量产生负面影响的预期相反。我们的方法专门调查了有记录的逃逸事件，与之前研究养殖鲑鱼对野生捕获量的潜在更广泛影响形成对比。这种方法更为保守，但减轻了一些观察性研究中始终存在的潜在混杂源。成功分析钓鱼者对养殖鲑鱼逃逸的报告需要高数据质量，特别是因为在苏格兰数据中，养殖鲑鱼的报告是一个相对罕见的事件。因此，作为我们分析的一部分，我们回顾了确定养殖起源的潜在敏感性和特异性的研究。文献中的特异性估计通常较高，使得我们进行的这种形式的分析成为可能。
