Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 4143
Title: Evaluating alternative strategies for minimizing unintended fitness consequences of cultured individuals on wild populations
Author: Marissa L. Baskett, Robin S. Waples
Publication Year: 2012
Journal: Conservation Biology
Volume: 27
Issue: 1
Pages: 83-94
Keywords: hatcheries, artificial propagation, domestication selection, rapid evolution, migration load, quantitative genetic model, Oncorhynchus spp.,hatcheries,

Artificial propagation strategies often incur selection in captivity that leads to traits that are
maladaptive in the wild. For propagation programs focused on production rather than demographic contribution to wild populations, effects on wild populations can occur through unintentional escapement or the need to release individuals into natural environments for part of their life cycle. In this case, 2 alternative management strategies might reduce unintended fitness consequences on natural populations: (1) reduce selection in captivity as much as possible to reduce fitness load (keep them similar), or (2) breed a separate population to reduce captive-wild interactions as much as possible (make them different). We quantitatively evaluate these 2 strategies with a coupled demographic–genetic model based on Pacific salmon hatcheries that incorporates a variety of relevant processes and dynamics: selection in the hatchery relative to the wild, assortative mating based on the trait under selection, and different life cycle arrangements in terms of hatchery release, density dependence, natural selection, and reproduction. Model results indicate that, if natural selection only occurs between reproduction and captive release, the similar strategy performs better. However, if natural selection occurs between captive release and reproduction, the different and similar strategies present viable alternatives to reducing unintended fitness consequences because of the greater opportunity
to purge maladaptive individuals. In this case, the appropriate approach depends on the feasibility of each strategy and the demographic goal (e.g., increasing natural abundance, or ensuring that a high proportion of natural spawners are naturally produced). In addition, the fitness effects of hatchery release are much greater if hatchery release occurs before (vs. after) density-dependent interactions. Given the logistical challenges to achieving both the similar and different strategies, evaluation of not just the preferred strategy but also the consequences of failing to achieve the desired target is critical.

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Theme: Recovery, Rebuilding and Sustainability of Marine and Anadromous Species
Foci: Investigate ecological and socio-economic effects of alternative management strategies or governance structures.
Maximize effectiveness and minimize impacts of artificial propagation in recovery, rebuilding and stock sustainability