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Dryad

Size, connectivity and edge effects of stream habitats explain spatiotemporal variation in brown trout (Salmo trutta) density

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Sep 07, 2021 version files 172.87 KB

Abstract

Ecological theory postulates that size and isolation of habitat patches impact the colonization/extinction dynamics that determine community species richness and population persistence. Given the key role of lotic habitats for life history completion in rheophilic fish, evaluating how the distribution of swift-flowing habitats affects the abundance and dynamics of subpopulations is essential. Using extensive electrofishing data, we show that merging island biogeography with meta-population theory, where lotic habitats are considered as islands in a lentic matrix, can explain spatiotemporal variation in occurrence and density of brown trout (Salmo trutta). Subpopulations in larger and less isolated habitat patches had higher average densities and smaller between-year density fluctuations. Larger habitat patches also had lower predicted risk of excessive zero catches, indicative of lower extinction risk. Trout density further increased with distance from the edge of adjacent lentic habitats with predator (Esox lucius) presence, suggesting that edge- and matrix-related mortality contributes to the observed patterns. These results can help reduce the negative impacts that habitat loss and fragmentation have on biodiversity, by stressing the importance of suitable habitat size and connectivity, and aid in prioritization of habitat restoration, dam removal and reintroduction programs aimed at vitalizing declining and locally extinct riverine fish populations.