Lepidurus arcticus (the Arctic tadpole shrimp) is a vulnerable keystone species in Arctic and alpine water bodies where its occurrence and population size may influence the viability and life history traits of resident salmonids. Using data from a Norwegian mountain hydropower reservoir, Aursjoen, we illustrate how reduced availability of L. arcticus as prey resulted in the reduced condition, growth and delayed maturation of resident brown trout (Salmo trutta). We further link changes in the relative abundance of L. arcticus as prey to changing reservoir conditions, e.g. water level changes in the spring period, thereby establishing an indirect link between reservoir operation regimes and brown trout population traits. While no evidence for decreased brown trout survival was found, the results indicate that alternative brown trout prey resources, i.e. the small chydorid cladoceran Eurycercus lamellatus, do not appear to have successfully offset the caloric loss from reduced consumption of large-sized L. arcticus. Although the fundamental explanation for the observed L. arcticus collapse remains largely unknown, the present findings provide strong evidence that this vulnerable crustacean species can affect the abundance, viability and life history traits of valued resident salmonid populations in oligotrophic alpine lakes and reservoirs exposed to climate- and hydropower-driven changes in water levels and temperature.

中文翻译：

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Lepidurus arcticus 可用性降低对山地水库褐鳟生活史特征的影响

Lepidurus arcticus（北极蝌蚪虾）是北极和高山水体中一种脆弱的关键物种，其发生和种群规模可能会影响常住鲑鱼的生存能力和生活史特征。我们使用来自挪威山地水电站 Aursjoen 的数据说明了 L. arcticus 作为猎物的减少如何导致常住褐鳟鱼 (Salmo trutta) 的条件、生长和成熟延迟。我们进一步将 L. arcticus 作为猎物的相对丰度的变化与不断变化的水库条件联系起来，例如春季水位变化，从而在水库运行制度和褐鳟鱼种群特征之间建立间接联系。虽然没有发现褐鳟鱼存活率下降的证据，但结果表明替代褐鳟鱼的猎物资源，即，小型 chydorid 枝角类 Eurycercus lamellatus，似乎并没有成功抵消因减少大型 L. arcticus 的消耗而造成的热量损失。尽管观察到的 L. arcticus 坍塌的基本解释在很大程度上仍然未知，但目前的研究结果提供了强有力的证据，表明这种脆弱的甲壳类动物可以影响暴露于气候的贫营养高山湖泊和水库中有价值的常住鲑鱼种群的丰度、生存能力和生活史特征- 以及水电驱动的水位和温度变化。