Effects of Physiological Condition on Aspects of Repeat Spawning in Female Steelhead Reconditioned in Captivity

Abstract

Physiological condition (hereafter shortened to “condition”) influences survival, spawning schedules, and reproductive effort in salmonids. In iteroparous females, the effects of first spawning on condition could result in trade‐offs with future reproduction, mediated by postspawning survival, repeat spawning schedule (i.e., consecutive or skip spawning), or reproductive effort. However, which aspects of condition affect these outcomes and when they are sensitive to condition are not well understood. These issues were examined in highly energy‐depleted hatchery‐origin female summer steelhead Oncorhynchus mykiss that were undergoing postspawning reconditioning in captivity. Measures of condition and reproductive characteristics (i.e., fecundity, egg size, and total egg mass [TEM]) at first spawning were examined for their effects on postspawning survival and future spawning schedules, and condition was tracked during reconditioning to examine effects on reproductive characteristics at repeat spawning. The levels of plasma osmolality and triglycerides measured at first spawning were positively correlated with survival probability, suggesting that survival depends on the ability to maintain homeostasis and access stored energy. Surprisingly, size‐standardized TEM measured at first spawning was positively correlated with the probability of consecutive spawning, providing no support for the hypothesized trade‐off between current and future reproduction. This finding instead suggests that both first‐spawning reproductive effort and consecutive spawning may be influenced by condition at earlier points. Plasma triglycerides and growth rates at sampling points 10–20 weeks after first spawning were strongly correlated with size‐standardized egg size and TEM at consecutive spawning, suggesting that reproductive effort and its allocation to egg size and fecundity depend on energetic status during early oogenesis. These results indicate that condition influences survival, repeat spawning schedules, and reproductive characteristics in female steelhead up to a year or more before repeat spawning. If more broadly applicable, these relationships could provide insight into the mechanisms that link environmental conditions with reproductive characteristics in salmonids and other species.

Live Freshwater Parasite, Salmincola californiensis (Copepoda: Lernaeopodidae), on the Gills of an Ocean-Migrating Steelhead Trout (Oncorhynchus mykiss) and Discussion on the Origin and Survival of the Parasite at Sea

“…As stated above, North American populations of S. californiensis are found from California northward through Colorado, Oregon, Idaho, Wyoming, Washington, British Columbia up to Alaska, and this parasite has been recorded from steelhead trout in California (Shapovalov and Taft, 1954), Washington (Barndt and Stone, 2003), and Idaho (Jenkins et al, 2020). Arai and Mudry (1983) also reported S. californiensis from steelhead trout or rainbow trout (reported as Salmo gairdneri ) in British Columbia.…”

“…The geographical distribution of S. californiensis has been well documented to date. In North America, the species is native to California (Wilson, 1915, 1916; Shapovalov and Taft, 1954; Kabata, 1969; Jennings and Hendrickson, 1982), Oregon (Kabata, 1969; Beeman et al, 2015; Monzyk et al, 2015; Herron et al, 2018; Murphy et al, 2020; Neal et al, 2021), Washington (Wilson, 1916; Kabata, 1969; Bailey and Margolis, 1987; Chigbu, 2001; Barndt and Stone, 2003), Idaho (Wilson, 1915, 1916; Kabata, 1969; Jenkins et al, 2020), Colorado (Wilson, 1916; Kabata, 1969; Hargis et al, 2014; Vigil et al, 2016), Wyoming (Kabata, 1969), and Alaska (Moles, 2007), the western U.S.A., and to British Columbia, western Canada (Kabata, 1969; Arai and Mudry, 1983; Bailey and Margolis, 1987). In Asia, the species occurs in Kamchatka, Primorsky Krai, and Sakhalin, Russia (Shedko, 2005; Shedko et al, 2005; Sokolov et al, 2012) and in Hokkaido and Honshu, Japan (Hoshina and Suenaga, 1954; Kabata, 1969; Hoshina and Nishimura, 1976; Nagasawa and Urawa, 2002; Nagasawa et al, 2018).…”

A genomic region associated with iteroparous spawning phenology is linked with age‐at‐maturity in female steelhead trout

“…In iteroparous fishes including O. mykiss, signaling through ERβ has been proposed to prime the liver, the primary site of vitellogenesis, to respond to estradiol early in gonadal recrudescence (Nelson & Habibi, 2013). Estradiol-17β, the circulating estrogen whose pattens of expression immediately following spawning shows inconsistent association with consecutive versus skip spawning, is nonetheless a clear marker of rematuration in consecutive spawners by 20 weeks post-spawn (Jenkins et al, 2020(Jenkins et al, , 2023. Variation in the expression of ERβ or its sensitivity to estradiol could theoretically moderate the proclivity of individuals to remature immediately or delay rematuration.…”

“…Samples consisted of two pairs of consecutive or skip spawning females reconditioned at two facilities in the interior Columbia River Basin, with spawning phenotype determined by plasma estradiol-17β assay after 20 weeks of reconditioning (Figure 1) (Hatch et al, 2013;Jenkins et al, 2019Jenkins et al, , 2020Jenkins et al, , 2023Pierce et al, 2017).…”

“…This implies that the critical processes determining the ability to remature the following season includes energetic status prior to maiden spawning as well as resource availability during the immediate post-spawn period (Jenkins et al, 2023;Pierce et al, 2017). However, since many females did not remature despite post-spawn feeding and similarity in condition assessments at spawning (35%-75% rematuration; Pierce et al, 2017;Jenkins et al, 2020Jenkins et al, , 2023), it appears that individual energetic status thresholds differ, and so genetic factors influencing this threshold and the ability to mobilize and direct energy flows to initiate a subsequent reproductive cycle likely also play an important role.…”