Sex-specific patterns of lifetime reproductive success in single and repeat breeding steelhead trout (Oncorhynchus mykiss) |
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Authors: | Todd R Seamons Thomas P Quinn |
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Institution: | (1) School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, WA 98195, USA |
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Abstract: | All other things being equal, the lifetime reproductive success (LRS) of iteroparous and semelparous individuals should scale
with the number of breeding seasons. Deviations from this relationship may occur for many reasons, including age- or size-related
fecundity or life history trade-offs, which may differ between sexes. We used 19 brood years of DNA parentage analysis in
a small (N = 4–143 year−1) wild, unexploited population of steelhead trout (Oncorhynchus mykiss) to compare the LRS of individuals that spawned only once “one time spawners” (OTS), N = 355 male, 371 female] to those spawning twice “repeat spawners” (RPS), N = 13 male, 49 female]. Female RPS had nearly twice the LRS of female OTS (1.17 offspring per female vs 0.91 offspring per
female), whereas male RPS had nearly three times the LRS of male OTS (1.54 offspring per male vs 0.57 offspring per male).
Female RPS produced slightly more adult offspring during their second breeding season than their first (0.78 vs 0.82 offspring
per female); however, male RPS produced all of their adult offspring in their second breeding season (0 vs 1.54 offspring
per male). The additional growth in body size of males between breeding seasons may give them an advantage in their second
breeding season, but the lack of offspring produced in their first season suggests a trade-off between survival and future
reproduction that was not expressed in females. |
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