Evans, Allen F. et al. “Identification and Enumeration of Steelhead Kelts at a Snake River Hydroelectric Dam.” Transactions of the American Fisheries Society 133 (2004): 1089-1099. (reviewed by Bethany Parkyn)
Summary:
In the past, most efforts to increase survival rates of anadromous salmonids (those that migrate from freshwater to saltwater and back) have focused on measures to help juveniles headed downstream through hydroelectric dams. There has been little, if any, focus on the migratory passages of anadromous iteroparous steelhead trout (fish who survive spawning to migrate and spawn again). To rectify the situation, the authors of this article set out with several goals: to enumerate the kelts (postspawning trout headed back to the ocean) passing through Lower Granite Dam on the Snake River, to determine their sex and run timing, and also to analyze the effectiveness of visual signals previously used to distinguish kelts from prespawners.
The authors used ultrasounds of gonads to differentiate between juvenile trout and kelts, and found that 94.6% of adult steelhead counted were kelts, compared to the much more meager number of 18% identified by visual means. They also found that only about 33% of the kelts were male, which suggests that high competition in the spawning grounds takes a large toll on the male population, and also possibly that females leave the spawning grounds before males (the study was done in 10 weeks between April and June 2000). Females were identified based on their egg mass and number, while males were slightly more difficult to classify, and as a result, some misclassifications may be present in the data, although the authors are confident that accuracy was generally very good. They also concluded that past visual identification standards were hugely inaccurate, and that kelts are actually brighter in color and in better condition than prespawners, not the other way around as previously assumed.
The data showed that with increased protection efforts focused specifically on aiding kelts in passage around the dams, iteroparity rates could potentially be vastly improved. However, in the efforts to help the kelts, the authors cautioned against implementing any measures that might hinder prespawners in their migrations.
Critique:
I enjoyed this article because it hopeful that iteroparity rates for steelhead in the Snake River could be improved. The data was presented with conviction, and the authors put forth several suggestions to improve migration of kelts, which include reconditioning practices, the implementation of practices involving transportation around dams (which is consistent with the current practices for smolts) and also increased protection from turbine intakes constructed specifically for adults. They found that ultrasounds were an effecting and noninvasive method of identifying kelts, determining their sex and also enumerating them. The data is relatively recent and certainly appropriate for further discussion today.
Robert D. Clark Honors College, University of Oregon
HC 441: Science Colloquium, Columbia River Ecology
Fall term, 2005
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