Red king crab, , was commercially important around Kodiak, Alaska, USA, in the 1960s and 1970s; however, the stock crashed in the late 1970 s and has remained closed since 1983. The lack of recovery inspired consideration of stock enhancement through the release of hatchery-reared juveniles as a means to bolster the wild population. We examined the effects of release timing on survival of hatchery-reared red king crab by releasing juveniles in June, August, and September 2015 in Trident Basin, Kodiak. We monitored densities inside and outside of release plots for six months using quadrat counts to determine loss and emigration rates. Relative predation risk was determined using tethering experiments performed after each release, and predator densities were quantified using quadrat counts and predator transect counts. Initial mortality over the first 24 h was approximately 53%, and subsequent mortality rates decreased with month-of-release, likely due to a combination of larger size-at-release and seasonal changes in predation. Although predator density was consistent over time, relative predation risk of tethered crabs decreased with season, suggesting later releases may be beneficial. However, the extended hatchery rearing period needed for later releases presents other challenges, including cannibalism, and the potential for developing maladaptive traits. Stock enhancement programs must balance these trade-offs to maximize overall success. Early releases of small juveniles immediately after settlement may be optimal if large-scale hatchery communal rearing results in significant juvenile production loss and/or hatchery conditioning is impractical.

中文翻译：

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优化红帝王蟹种群增殖放流策略：放流时间的影响

20 世纪 60 年代和 1970 年代，红帝王蟹在美国阿拉斯加州科迪亚克地区具有重要的商业价值；然而，该种群在 1970 年代末崩溃，自 1983 年以来一直处于关闭状态。由于缺乏恢复，人们考虑通过释放孵化场饲养的幼体来增强种群数量，以此作为增加野生种群的一种手段。我们于 2015 年 6 月、8 月和 9 月在科迪亚克岛三叉戟盆地释放幼蟹，研究了释放时间对孵化场饲养的红王蟹存活率的影响。我们使用样方计数来监测释放地块内部和外部的密度六个月，以确定损失和迁移率。使用每次释放后进行的系绳实验确定相对捕食风险，并使用样方计数和捕食者横断面计数来量化捕食者密度。前 24 小时内的初始死亡率约为 53%，随后的死亡率随着释放月份的增加而下降，这可能是由于释放时体型较大和捕食季节变化的共同作用。尽管捕食者密度随着时间的推移保持一致，但系留螃蟹的相对捕食风险随着季节的变化而降低，这表明较晚的释放可能是有益的。然而，后期释放所需的延长孵化场培育期也带来了其他挑战，包括同类相食以及产生适应不良性状的可能性。库存增强计划必须平衡这些权衡，以最大限度地提高整体成功。如果大规模孵化场公共饲养导致幼鱼产量显着下降和/或孵化场调节不切实际，则在定居后立即早期释放小型幼鱼可能是最佳选择。