No abstract

Hybridization between distinct populations of salmon can cause fitness loss (outbreeding depression), and may result in reduced survival. The erosion of fitness-related traits such as homing ability and change in family size distribution may underlie reduced survival. Outbreeding depression was investigated in two independent experiments that made hybrids between geographically separated and genetically divergent pink salmon populations. Control crosses were made from male and female Auke Creek (Southeast Alaska) pink salmon and hybrid crosses were between Auke Creek females and Pillar Creek (Kodiak Island, about 1000km away) males. Parentage assignment from microsatellite analysis improved estimates of survival and straying, and was used to examine variation in family size. The return rates of even-broodyear Fi control and hybrid fish were similar, but the odd-broodyear Fj control returns exceeded hybrid returns. The F2 control returns exceeded hybrid returns in both the even-and oddbroodyears. Hybridization did not impair homing ability; weekly surveys in nearby (~ 1km) Waydelich Creek revealed similar straying rates from Auke Creek by both hybrid and control fish in all years. Family data were available only for even-broodyear returns; hybridization did not increase the index of variability (ratio of variance to mean) in family size in these years. Outbreeding depression in hybrids of geographically separated populations demonstrates the potential for introgression of normative fish to erode natural production.

This study investigated whether repeated use of limited spawning grounds (i.e., redd superimposition) by pink salmon (Oncorhynchus gorbuscha) can cause density-dependent mortality. Loss of eggs from part of Auke Creek, Alaska, was estimated from a series of mark-recapture experiments and maximum likelihood models. The number of eggs lost per day during the 5-week spawning season and for 2 weeks afterward was roughly proportional to spawner abundance and weakly related to stream discharge. Freshets after cessation of spawning induced negligible egg loss. The maximum daily egg loss estimated by one model was 398 000 eggs (80% CI = 267 000 - 1 581 000) or equivalently a loss of about 300 female spawners when the daily spawner abundance (both male and female) in the study area was at most 1000.

Quantitative genetic variation of development rate was evident among 20 half-sib and 40 full-sib families within each of two seasonally separate components of a population of pink salmon (Oncorhynchus gorbuscha) (H o : no sire effect on temperature units at hatch, P < 0.02). Differences between averages of families spawned 3 weeks apart may have had genetic or environmental sources (e.g., in constant 8°C, early embryos hatched at 606 temperature units, and late embryos, at 625). Statistical interactions between paternal effects and environment (embryos were cultured in four temperature regimes, two simulated natural regimes and two constant temperatures; H o : no sire by regime interaction effect on temperature units at hatch, P < 0.09) were weak evidence that genotype by environment interactions contributed to variation. Paternal effects in analysis of variance (evidence of additive genetic variation) were detected only at later stages. Evidences of genetic variation and of interactions between genotypes and environments are pertinent to resource conservation because they suggest that harvest management or hatchery practice have the potential to reduce genetic variation in salmon populations.Résumé : Une variation génétique quantitative du taux de développement était apparente chez 20 familles de demifrères et 40 familles de plein-frères au sein de deux composantes saisonnières distinctes d'une population de saumon rose, Oncorhynchus gorbuscha. (H o : aucun effet du père sur le nombre d'unités de température au moment de l'éclosion, P < 0,02). Les écarts notés entre les moyennes des familles dont la fécondation présentait trois semaines d'intervalle peuvent s'expliquer par des facteurs génétiques ou environnementaux (p. ex. : à une température constante de 8°C l'éclosion des embryons se produisait à 606 unités de température pour les plus hâtifs et à 625 pour les plus tardifs). Les interactions statistiques entre les effets paternels et l'environnement (embryons élevés sous quatre régimes de température, deux régimes naturels simulés et deux à température constante; H o : aucune interaction père-régime sur les unités de température à l'éclosion, P < 0,09) constituaient un indice faible du faible apport à la variation des effets de l'environnement sur le génotype. Une analyse de variance des effets paternels (évidence d'une variation génétique additive) n'a permis de mettre ces derniers en évidence qu'aux stades ultérieurs. L'existence de signes de variation génétique et d'interactions entre les génotypes et les environnements s'avère pertinente pour la conservation des ressources car elle indique que la gestion de la récolte ou les pratiques des piscicultures pourraient influer sur la variation génétique des populations de saumon.[Traduit par la Rédaction]

Hatcheries support nearly all major fisheries for Pacific salmon (Oncorhynchus spp.) and steel‐head (anadromous O. mykiss) in the Pacific Northwest. However, hatcheries have been a major source of controversy for over 30 years. The Hatchery Scientific Review Group (HSRG) was tasked by Congress to identify solutions to well‐known problems so hatcheries could better meet their goals of supporting sustainable fisheries and assisting with the conservation of natural populations. We reviewed over 100 facilities and 200 programs and identified three principles of hatchery reform: (1) goals for each program must be explicitly stated in terms of desired benefits and purposes; (2) programs must be scientifically defensible; and (3) hatchery programs must respond adaptively to new information. We also identified several emerging issues critical to the success of hatcheries. We concluded that hatcheries must operate in new modes with increased scientific oversight and that they cannot meet their goals without healthy habitats and self‐sustaining, naturally‐spawning populations.