Search

We quantified the population dynamics and life history diversity of seven brood years of coho salmon (Oncorhynchus kisutch) using a life-cycle approach. Four life history patterns, composed of fry, fry-nomad, parr, and yearling migrants indicated the importance of connectivity and access to a full range of freshwater and estuarine rearing environments through the year. Survival of each life history type varied annually with the yearling migrants contributing an average of 70% to the spawners in all but one return year. Fifty-eight percent of the spawners of the 2013 return year had an estuarine rearing strategy, primarily parr migrants that overwintered in the estuary. Fry migrants, thought to be surplus production, were consistently observed in the estuary and represented in the returning spawners. The annual contribution of alternative rearing strategies to the spawners may support the resilience and viability of the population. We recommend that life cycle models of coho salmon account for the contribution of estuary migrants to the productivity and persistence of coho salmon in support of management and restoration of populations. Nous avons quantifie la dynamique de la population et la diversite des cycles biologiques de saumons cohos (Oncorhynchus kisutch) de sept annees d'eclosion en utilisant une approche axee sur le cycle biologique. Quatre types de cycles biologiques composes d'alevins, d'alevins nomades, de tacons et de migrants d'un an, font ressortir l'importance de la connectivite et de l'acces a tout un eventail de milieux de croissance estuariens et d'eau douce au fil de l'annee. Pour chacun des types de cycles biologiques, la survie varie annuellement, les migrants d'un an comptant en moyenne pour 70 % des geniteurs pour toutes les annees de retour sauf une. Cinquante-huit pour cent des geniteurs de l'annee de retour 2013 presentaient une strategie de croissance estuarienne, principalement des tacons migrants qui passaient l'hiver dans l'estuaire. Des alevins migrants, qui constitueraient une production excedentaire, etaient uniformement observes dans l'estuaire et representes au sein des geniteurs de retour. Les contributions annuelles de differentes strategies de croissance au nombre des geniteurs pourraient appuyer la resilience et la variabilite de la population. Nous recommandons que des modeles de cycle biologique du saumon coho soient utilises pour expliquer la contribution des individus a migration estuarienne a la productivite et a la persistance des saumons cohos afin d'appuyer la gestion et le retablissement des populations. [Traduit par la Redaction], Introduction Life history variations in juvenile coho salmon may represent alternative pathways that strengthen population resilience and viability in light of habitat loss and environmental change, as has been shown [...]

A novel application of full-duplex passive integrated transponder (PIT) tag technology was used to investigate movements of individual subyearling Chinook salmon (Oncorhynchus tshawytscha; fork length ≥60 mm) into and out of tidally flooded salt marsh habitat in the Salmon River estuary, Oregon, USA. PIT interrogation was effective, with mean tag detection ≥92%. Salmon movement peaked late during both flood and ebb tide periods, indicating that salmon did not drift passively. Most movements were in the direction of tidal currents, but 20% of individuals entered the channel against the ebbing tide. Individuals occupied the intertidal channel for a median 4.9 h and as long as 8.9 h per tidal cycle, and few were detected moving when water depth was Resume: Une utilisation inedite de la technologie des transpondeurs passifs integres a transmission bidirectionnelle simultanee (etiquettes PIT) a servi a etudier les deplacements de saumons chinook (Oncorhynchus tshawytscha; longueur a la fourche ≥60 mm) ages de moins d'un an lors de leur entree ou sortie d'un habitat de marais salant inonde par la maree dans l'estuaire de la riviere Salmon, Oregon, E .-U. Le systeme d'interrogation des PIT est efficace avec une detection moyenne de ≥92 % des etiquettes. Les deplacements des saumons atteignent un maximum a la findes marees montantes et descendantes, ce qui indique que les saumons ne derivent pas passivement. La plupart des deplacements se font dans le sens des courants de maree, mais 20 % des individus penetrent dans le chenal contre la maree descendante. Les individus se retrouvent dans le chenal interdital pour une mediane de 4,9 h et jusqu'a 8,9 h pendant un cycle de maree et certains ont ete observes se deplacer dans des eaux de < 0,4 m de profondeur. Quelques individus utilisent le chenal pendant plusieurs cycles successifs de maree et d'autres y penetrent de facon intermittente pendant une periode aussi longue que 109 jours. En utilisant une approche basee sur l'individu, nous decrivons la diversite des comportements de jeunes saumons chinook dans un chenal de marais, ce qui fournit une perspective sur la valeur de tels habitats pour la conservation et la restauration des populations de saumons. [Traduit par la Redaction], Introduction During their juvenile migration from freshwater to marine habitat, ocean-type Chinook salmon (Oncorhynchus tshawytscha) may rear for prolonged periods in subsidiary and blind channel networks that connect mainstem estuarine [...]

To increase survival of diverse Columbia River salmon populations and life history types, we developed a landscape framework for habitat restoration to assess and reduce habitat fragmentation, and thereby improve habitat functions. For the last two decades, aquatic habitat has been restored in the Columbia River Estuary (U.S.A.) to aid salmon and steelhead (Oncorhynchus spp.) listed under the Endangered Species Act. The 234‐km long estuary exhibits tidal to fluvial gradients in hydrology, sedimentology, and ecology, punctuated by large tributary rivers, cities, and land uses; it has lost two‐thirds of its historical floodplains and wetlands to development. Since 2009, an expert panel has assessed potential benefits of proposed restoration projects based on habitat "opportunity" (accessibility to juvenile salmon) and "capacity" (attributes supporting salmon production). These criteria favored large restoration projects located near the mainstem river, but they were insufficient for assessing a project's benefits due to geographic location relative to existing habitat. Our landscape framework applies the concept of restoring and conserving habitat "stepping stones" of appropriate size and location to benefit juvenile salmon growth and survival throughout their estuary residency and migration. We also compared contemporary and historical landscape conditions to identify restoration priorities. We improved our restoration project assessments by evaluating each project's benefits to juvenile salmon according to its location in the estuary relative to other habitat. Our approach operationalizes landscape ecology‐based decisions within the Columbia River Estuary for migratory salmon and is applicable to other large estuary systems with migratory aquatic species. [ABSTRACT FROM AUTHOR]