Rearing in natural and recovering tidal wetlands enhances growth and life‐history diversity of Columbia Estuary tributary coho salmon Oncorhynchus kisutch population

Abstract

This study provides evidence of the importance of tributary tidal wetlands to local coho salmon Oncorhynchus kisutch populations and life-history diversity. Subyearling and, to a lesser extent, yearling O. kisutch life histories utilized various estuary habitats within the Grays River, a tidal freshwater tributary of the Columbia River estuary, including restoring emergent wetlands and natural forested wetlands. Migration timing data, size distributions, estuary residence and scale patterns suggest a predominance of subyearling migrant life histories, including several that involve extended periods of estuary rearing. Estuarine-rearing subyearling O. kisutch exhibited the greatest overall growth rates; the highest growth rates were seen in fish that utilized restoring emergent wetlands. These results contrast with studies conducted in the main-stem Columbia River estuary, which captured few O. kisutch, of which nearly all were hatchery-origin yearling smolts. Restoration and preservation of peripheral and tributary wetland habitats, such as those in the Grays River, could play an important role in the recovery of natural O. kisutch populations in the Columbia River and elsewhere.

Juvenile coho salmon movement, growth and survival in a coastal basin of southern Oregon

“…Similar coho salmon fry migration to estuarine habitats has been reported by studies in Oregon, Washington, British Columbia and Alaska (Hartman et al., ; Miller & Sadro, ; Koski, ; Craig et al. ). The cause of such early estuarine entry has been attributed to either competitive exclusion (Chapman, ) or abiotic factors (e.g., high stream discharge; Hartman et al., ), but it is likely that various mechanisms influence this behaviour.…”

Spatial and Temporal Patterns in Smolt Survival of Wild and Hatchery Coho Salmon in the Salish Sea

“…found for some streams in our study area (Craig et al 2014;Bennett et al 2015). For this second method, spawner escapement estimates were expanded by exploitation rate, either modeled or calculated using tag recoveries of a nearby population, in order to include the fish retained in fisheries in the survival estimates.…”

Floodgate Operations and Fish Communities in Tidal Creeks of the Lower Fraser River (British Columbia, Canada)

“…Due to the timing of sampling, our study did not fully assess the impacts of floodgate operations on juvenile salmon. Although tidal creeks and wetlands can be key rearing habitats for juvenile coho and Chinook salmon in the spring and early summer, most individuals are unlikely to remain in these habitats by late summer (Levy and Northcote 1982;Craig et al 2014;Scott et al 2016). Our fish sampling regime was focused on the late summer and thus provided a snapshot of impacts for this season when hypoxic conditions occur near floodgates (Gordon et al 2015;Scott et al 2016).…”

“…Although we know that many floodgates may remain closed for weeks to months during seasonal high flows (i.e., the freshet) (Thomson 2005), there are limited data on floodgate operations for the rest of the year. Tidal creeks and wetlands represent important rearing habitats for juvenile coho and Chinook salmon (Oncorhynchus kisutch, O. tshawytscha) (Levy and Northcote 1982;Craig et al 2014); however, floodgates can diminish water quality and restrict access to these habitats (Gordon et al 2015;Scott et al 2016). Given aging infrastructure and increased flood risk due to sea level rise and changing river hydrographs, the region is undergoing a strategic flood management planning process (Fraser Basin Council 2014).…”