Spatial covariation of fish population vital rates in a stream network |
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Authors: | Jun-ichi Tsuboi Kentaro Morita Yusuke Koseki Shinsuke Endo Genki Sahashi Daisuke Kishi Takeshi Kikko Daisuke Ishizaki Masanori Nunokawa Yoichiro Kanno |
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Institution: | 1. Research Center for Freshwater Fisheries, National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, JP-321-1661 Nikko, Japan;2. Hokkaido National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Sapporo, Japan;3. Dept of Life Design, Faculty of Home Economics, Otsuma Women's Univ., Tokyo, Japan;4. Doutor Coffee Co. Ltd., Jin-nan, Shibuya, Tokyo, Japan;5. Gero Branch, Gifu Prefectural Research Inst. for Fisheries and Aquatic Environments, Gero, Japan;6. Shiga Prefectural Fisheries Experiment Station, Hassaka, Hikone, Shiga, Japan;7. Civil Engineering Research Inst. for Cold Region, Sapporo, Japan;8. Dept of Fish, Wildlife, and Conservation Biology, and Graduate Degree Program in Ecology, Colorado State Univ., Fort Collins, CO, USA |
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Abstract: | Animal populations are spatially structured in heterogeneous landscapes, in which local patches with differing vital rates are connected by dispersal of individuals to varying degrees. Although there is evidence that vital rates differ among local populations, much less is understood about how vital rates covary among local patches in spatially heterogeneous landscapes. In this study, we conducted a nine-year annual mark–recapture survey to characterize spatial covariation of survival and growth for two Japanese native salmonids, white-spotted charr Salvelinus leucomaenis japonicus and red-spotted masu salmon Oncorhynchus masou ishikawae, in a headwater stream network composed of distinctly different tributary and mainstem habitats. Spatial structure of survival and growth differed by species and age class, but results provided support for negative covariation between vital rates, where survival was higher in the tributary habitat but growth was higher in the mainstem habitat. Thus, neither habitat was apparently more important than the other, and local habitats with complementary vital rates may make this spatially structured population less vulnerable to environmental change (i.e. portfolio effect). Despite the spatial structure of vital rates and possibilities that fish can exploit spatially distributed resources, movement of fish was limited due partly to a series of low-head dams that prevented upstream movement of fish in the study area. This study shows that spatial structure of vital rates can be complex and depend on species and age class, and this knowledge is likely paramount to elucidating dynamics of spatially structured populations. |
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Keywords: | Bayesian analysis Cormack–Jolly–Seber models mark–recapture meta-population spatial heterogeneity stream salmonids |
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