A conservation hatchery population of Delta Smelt shows evidence of genetic adaptation to captivity after 9 generations

Genetic adaptation to captivity is a concern for threatened and endangered species held in conservation hatcheries. Here, we present evidence of genetic adaptation to captivity in a conservation hatchery for the endangered Delta Smelt (Fish Conservation and Culture Laboratory, University of California Davis; FCCL). The FCCL population is genetically managed with parentage analysis and the addition of wild fish each year. Molecular monitoring indicates little loss of genetic variation and low differentiation between the wild and conservation populations. Yet, we found an increase in offspring survival to reproductive maturity during the subsequent spawning season (recovery rate) in crosses that included one or both cultured parents. Crosses with higher levels of hatchery ancestry tend to produce a greater number of offspring that are recovered the following year. The recovery rate of a cross decreases when offspring are raised in a tank with fish of high levels of hatchery ancestry. We suggest changes in fish rearing practices at the FCCL to reduce genetic adaptation to captivity, as Delta Smelt numbers in the wild continue to decline and the use of FCCL fish for reintroduction becomes more likely.

对于保育孵化场饲养的受威胁与濒危物种来说，圈养遗传适应是一项亟需关注的问题。本研究针对濒危三角洲胡瓜鱼（Delta Smelt），于加州大学戴维斯分校鱼类保育与养殖实验室（Fish Conservation and Culture Laboratory, University of California Davis，简称FCCL）的保育孵化场中，提供了其发生圈养遗传适应的实证依据。FCCL种群通过亲权分析及年度野生鱼类引种开展遗传管理。分子监测结果表明，野生种群与保育种群间的遗传变异损耗极低，且遗传分化程度微弱。然而，本研究发现，当杂交组合包含一方或双方为孵化场繁育亲本时，后代在后续产卵季存活至繁殖成熟的比例（恢复率，recovery rate）显著提升。携带更高孵化场祖先血统占比的杂交组合，通常可产生更多次年可被回收的后代。若后代饲养于包含高孵化场血统个体的水族箱内，则该杂交组合的恢复率会出现下降。鉴于野生三角洲胡瓜鱼种群数量持续下滑，且利用FCCL种群进行物种再引入的可能性日益升高，我们建议调整FCCL的鱼类饲养规程，以降低其圈养遗传适应程度。