Physiological indices of seawater readiness in postspawning steelhead kelts

Ecology of Freshwater Fish
By:  and 



Management goals to improve the recovery of steelhead (Oncorhynchus mykiss) stocks at risk of extinction include increasing the proportion of postspawning fish that survive and spawn again. To be successful, postspawning steelhead (kelts) migrating downstream to the ocean must prepare physiologically and physically for a seawater transition. We sampled blood, gill filaments, and evaluated the external condition of migrating kelts from an ESA-listed population in the Snake/Columbia River system over two consecutive years to evaluate their physiological readiness for transition to seawater. We chose attributes often considered as measures of preparation for seawater in juveniles, including gill Na+,K+ ATPase activity, plasma electrolytes and hormones to consider factors related to external condition, size and sex. We found kelts in good external condition had plasma profiles similar to downstream-migrating smolts. In addition, we found more than 80% of kelts ranked in good external condition had smolt-like body silvering. We compared measures from migrating kelts with samples obtained from hatchery fish at the time of spawning to confirm that Na+, K+ ATPase activity in kelts was significantly elevated over spawning fish. We found significant differences in gill Na+, K+ ATPase activity in migrating kelts between the years of sampling, but little indication of influence of fish condition. We conclude that the postspawning steelhead sampled exhibited a suite of behaviours, condition and physiology characteristic of fish prepared for successful transition to a seawater environment.

Publication type Article
Publication Subtype Journal Article
Title Physiological indices of seawater readiness in postspawning steelhead kelts
Series title Ecology of Freshwater Fish
DOI 10.1111/eff.12130
Volume 24
Issue 1
Year Published 2015
Language English
Publisher Wiley Online Library
Contributing office(s) Idaho Cooperative Fish and Wildlife Research Unit
Description 11 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Ecology of Freshwater Fish
First page 112
Last page 122
Country United States
State Idaho;Washington
Online Only (Y/N) N
Additional Online Files (Y/N) N
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