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D.W. Rondorf

Publications and source records attributed to D.W. Rondorf.

At least 73 records · Page 4Linked to original sources
USGS1998

Effects of surgically and gastrically implanted radio transmitters on swimming performance and predator avoidance of juvenile chinook salmon ( Oncorhynchus tshawytscha )

Radiotelemetry data are often used to make inferences about an entire study population; therefore, the transmitter attachment method should be the one that least affects the study animal. Juvenile chinook salmon ( Oncorhynchus tshawytscha ) <120 mm in fork length (FL) with either gastrically or surgically implanted transmitters had significantly lower critical swimming speeds than control fish 1 and 19-23 days after tagging. For fish >120 mm FL, fish with gastric implants swam as well as controls 1 day but not 19-23 days after tagging. In contrast, fish with surgical implants swam as well as controls 19-23 days but not 1 day after tagging. During predation trials, fish with gastric or surgical implants were eaten by smallmouth bass ( Micropterus dolomieu ) in significantly greater numbers than controls. We do not recommend implanting transmitters (representing 4.6-10.4% of the fish's body weight) in fish <120 mm FL. Furthermore, surgical implants (representing 2.2-5.6% of the fish's body weight) may be the preferred method for biotelemetry studies of juvenile chinook salmon >120 mm FL.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1996

Incidence of Renibacterium salmoninarum infections in juvenile hatchery spring chinook salmon in the Columbia and Snake Rivers

From 1988 through 1992, we assessed the prevalence (frequency of occurrence) and severity (degree of infection) of Renibacterium salmoninarum (RS) among fish in marked groups of Columbia River basin and Snake River basin hatchery spring chinook salmon Oncorhynchus tshawytscha before release and during their seaward migration. During the study, prevalence of RS infection decreased (from >90% to <65%) in six of the eight hatchery groups. We attributed this decrease to changes in hatchery practices that reduced vertical and horizontal transmission. Fish from Snake River hatcheries had a higher prevalence of infection when sampled at dams (mean >90%) than in the hatchery (mean <70%), but there were no differences in similar comparisons of Columbia River fish. Although prevalence and severity of RS infection were not correlated in the groups studied, it appears that fish from the Snake River were more severely infected than those from the Columbia River. Some groups of Snake River fish had higher severity of infection at dams than in the hatchery, but infection in fish from Columbia River hatcheries did not change. These differences between Snake River and Columbia River fish might have resulted from differences in river conditions and the distances from hatcheries to dams.

Oregon, Washington↗
USGS1995

A non-lethal measure of smolt status of juvenile steelhead based on body morphology

A nonlethal morphometric method to assess smolt status of juvenile steelhead Oncorhynchus mykiss was validated. Fish were collected from hatcheries before release and during their seaward migration in a large river system. Fifteen anatomical landmarks were digitized from photographs of each fish, resulting in 34 morphometric characters based on a truss network. Principal component and canonical discriminant function analyses were used to assess smolt status. A single canonical variate was significantly correlated with gill Na + ,K + ‐ATPase activity, a commonly used measure of smolt status. This nonlethal method may be a useful measure of smolt status when sacrificing fish is not desirable or possible; it requires little training to perform, but it does require a larger sample size than some other methods.

Transactions of the American Fisheries Society↗
USGS1994

Assessing smoltification of juvenile spring Chinook salmon Oncorhynchus tshawytscha using changes in body morphology

A morphometric measure of smoltification of juvenile spring chinook salmon ( Oncorhynchus tshawytscha ) was developed and evaluated. Fish were collected from hatcheries in Washington and Idaho prior to release and at McNary Dam on the Columbia River during their downstream migration. Distances between 15 anatomical landmarks were digitized from photographs of each fish resulting in 34 morphometric characters for analysis. The canonical variate calculated from a discriminant function based on several principal components was evaluated as a measure of smoltification. The canonical variate was significantly correlated with gill Na + –K + ATPase activity, a commonly used measure of smoltification. Measuring the morphometric characters and calculating the canonical variate is a relatively simple procedure and can be performed with little harm to the fish. This method of smoltification assessment may be ideally suited to studies in which sacrificing fish is not possible, such as those involving threatened or endangered species, or when access to a laboratory for sample analysis is not available.

Canadian Journal of Fisheries and Aquatic Sciences↗