Relationship between effective population size, inbreeding, and adult fitness-related traits in a steelhead (Oncorhynchus mykiss) population released in the wild

Inbreeding is of concern in supportive breeding programmes in Pacific salmonids, Oncorhynchus spp, where the number of breeding adults is limited by rearing space or poor survival to adulthood, and large numbers are released to supplement wild stocks and fisheries. We reconstructed the pedigree of 6602 migratory hatchery steelhead (Oncorhynchus mykiss) over four generations, to determine the incidence and fitness consequences of inbreeding in a northwest USA programme. The hatchery maintained an effective population size, = 107.9 from F0 to F2, despite an increasing census size (N), which resulted in a decreasing Ne/N ratio (0.35 in F0 to 0.08 in F2). The reduced ratio was attributed to a small broodstock size, nonrandom transfers and high variance in reproductive success (particularly in males). We observed accumulation of inbreeding from the founder generation (in F4, percentage individuals with inbreeding coefficients Δf > 0 = 15.7%). Generalized linear mixed models showed that b...近交问题在太平洋鲑类大麻哈鱼属（Oncorhynchus spp.）的支持性繁育计划中始终备受关注：此类项目中繁育成体的数量常受限于养殖空间或成体存活率低下，且需大量放流个体以补充野生种群及渔业资源。本研究针对美国西北部的一项此类繁育项目，对6602尾洄游性孵化场养殖的硬头鳟（Oncorhynchus mykiss）开展了四代谱系重建，以明确近交的发生频率及其对适合度的影响。尽管普查种群数量（census size, N）逐年增长，但该孵化场从奠基代（F0）到第二代（F2）的有效种群大小（effective population size, Ne）始终维持在107.9，由此导致Ne/N比值持续走低：从F0代的0.35降至F2代的0.08。该比值下降的原因可归因于亲本群体规模偏小、个体非随机转移以及繁殖成功率的高方差（尤以雄性个体最为显著）。研究观察到自奠基代起近交程度不断累积：在F4代中，近交系数Δf>0的个体占比达15.7%。广义线性混合模型（Generalized linear mixed models）结果显示，b……