Abstract
In salmonid parentage‐based tagging (PBT) applications, entire hatchery broodstocks are genotyped, and subsequently, progeny can be nonlethally sampled and assigned back to their parents using parentage analysis, thus identifying their hatchery of origin and brood year (i.e., age). Inter‐ and intrapopulation variability in migration patterns, life history traits, and fishery contributions can be determined from PBT analysis of samples derived from both fisheries and escapements (portion of a salmon population that does not get caught in fisheries and returns to its natal river to spawn). In the current study of southern British Columbia coho salmon (Oncorhynchus kisutch) populations, PBT analysis provided novel information on intrapopulation heterogeneity among males in the total number of progeny identified in fisheries and escapements, the proportion of progeny sampled from fisheries versus escapement, the proportion of two‐year‐old progeny (jacks) produced, and the within‐season return time of progeny. Fishery recoveries of coho salmon revealed heterogeneity in migration patterns among and within populations, with recoveries from north and central coast fisheries distinguishing “northern migrating” from “resident” populations. In northern migrating populations, the mean distance between fishery captures of sibs (brothers and sisters) was significantly less than the mean distance between nonsibs, indicating the possible presence of intrapopulation genetic heterogeneity for migration pattern. Variation among populations in productivity and within populations in fish catchability indicated that population selection and broodstock management can be implemented to optimize harvest benefits from hatcheries. Application of PBT provided valuable information for assessment and management of hatchery‐origin coho salmon in British Columbia.
Highlights
Life history variability in salmonids, generally under both genetic and environmental control, is known to be condition‐dependent with the adoption of differing developmental pathways affected by a myriad of factors such as individual size, season, age, predation, and food availability
All coho salmon released since the late 1990s from most large hatcheries in southern British Columbia, Washington, and Oregon have been visually marked with an adipose fin clip to facilitate mark‐selective fisheries intended to target hatchery salmon and spare naturally spawned individuals
Does the presence of life history variation in hatchery fish impact the economic benefit derived from their harvest, and selective harvest practices can in turn lead to altered life history and phenology in exploited populations (Hard et al, 2008; Tillotson & Quinn, 2018)
Summary
Life history variability in salmonids, generally under both genetic and environmental control, is known to be condition‐dependent with the adoption of differing developmental pathways affected by a myriad of factors such as individual size, season, age, predation, and food availability. Evaluation of life history variation among and within hatchery populations can facilitate both selection of populations well suited for harvest augmentation and evaluation of the subsequent impacts of exploitation rates on the populations under enhancement Management of both genetic (broodstock selection and spawning protocols) and environmental (spawn timing, rearing conditions, ration levels) factors to affect hatchery fish characteristics and distributions and increase their utility may be possible. We use coho salmon PBT analysis based on genotyping of 304 variable SNPs to examine life history variation among and within hatchery coho salmon populations, with a focus on family differentiation in productivity and fishery contributions. We conclude that PBT analysis increases the scope for hatchery broodstock and fishery assessment to improve hatchery broodstock management for improved harvest contributions and reduced impact on natural populations
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