Department of Zoology, Oregon State University, Corvallis, OR 97331-2914, USA.
Mol Ecol. 2011 Mar;20(6):1263-76. doi: 10.1111/j.1365-294X.2010.04994.x. Epub 2011 Jan 19.
In order to increase the size of declining salmonid populations, supplementation programmes intentionally release fish raised in hatcheries into the wild. Because hatchery-born fish often have lower fitness than wild-born fish, estimating rates of gene flow from hatcheries into wild populations is essential for predicting the fitness cost to wild populations. Steelhead trout (Oncorhynchus mykiss) have both freshwater resident and anadromous (ocean-going) life history forms, known as rainbow trout and steelhead, respectively. Juvenile hatchery steelhead that 'residualize' (become residents rather than go to sea as intended) provide a previously unmeasured route for gene flow from hatchery into wild populations. We apply a combination of parentage and grandparentage methods to a three-generation pedigree of steelhead from the Hood River, Oregon, to identify the missing parents of anadromous fish. For fish with only one anadromous parent, 83% were identified as having a resident father while 17% were identified as having a resident mother. Additionally, we documented that resident hatchery males produced more offspring with wild anadromous females than with hatchery anadromous females. One explanation is the high fitness cost associated with matings between two hatchery fish. After accounting for all of the possible matings involving steelhead, we find that only 1% of steelhead genes come from residualized hatchery fish, while 20% of steelhead genes come from wild residents. A further 23% of anadromous steelhead genes come from matings between two resident parents. If these matings mirror the proportion of matings between residualized hatchery fish and anadromous partners, then closer to 40% of all steelhead genes come from wild trout each generation. These results suggest that wild resident fish contribute substantially to endangered steelhead 'populations' and highlight the need for conservation and management efforts to fully account for interconnected Oncorhynchus mykiss life histories.
为了增加日渐减少的鲑鱼种群数量，补充计划会有意将在孵化场饲养的鱼类放归野外。由于孵化场出生的鱼类通常比野生出生的鱼类适应性差，因此估计从孵化场向野生种群的基因流动率对于预测对野生种群的适应成本至关重要。虹鳟（Oncorhynchus mykiss）既有淡水居留型，也有溯河洄游型（入海型）生活史形式，分别称为虹鳟和海鳟。“残留化”（成为居民而不是按照预期去海）的幼鱼为从孵化场到野生种群的基因流动提供了以前未测量的途径。我们结合使用亲子关系和祖孙关系方法，对俄勒冈州胡德河的三代虹鳟的谱系进行分析，以确定溯河洄游鱼类的缺失亲代。对于只有一个溯河洄游亲代的鱼类，83%被鉴定为具有居留性父亲，而 17%被鉴定为具有居留性母亲。此外，我们还记录到居留性孵化场雄性与野生溯河洄游雌性的交配比与孵化场溯河洄游雌性的交配产生更多的后代。一种解释是两个孵化场鱼类之间的交配与高适应成本有关。在考虑了所有可能涉及虹鳟的交配之后，我们发现只有 1%的虹鳟基因来自残留化的孵化场鱼类，而 20%的虹鳟基因来自野生居民。另外 23%的溯河洄游虹鳟基因来自两个居留性亲代之间的交配。如果这些交配反映了残留化孵化场鱼类和溯河洄游伴侣之间的交配比例，那么每一代大约有 40%的虹鳟基因来自野生鳟鱼。这些结果表明，野生居民鱼类对濒危的虹鳟“种群”做出了重大贡献，并强调需要进行保护和管理工作，以充分考虑到虹鳟相互关联的生活史。
