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Filters: Tags: Environmental Biology of Fishes (X) > partyWithName: Jason B. Dunham (X)

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We described and predicted spatial variation in marine migration (anadromy) of female Oncorhynchus mykiss in the John Day River watershed, Oregon. We collected 149 juvenile O. mykiss across 72 sites and identified locations used by anadromous females by assigning maternal origin (anadromous versus non-anadromous) to each juvenile. These assignments used comparisons of strontium to calcium ratios in otolith primordia and freshwater growth regions to indicate maternal origin. We used logistic regression to predict probability of anadromy in relation to mean annual stream runoff using data from a subset of individuals. This model correctly predicted anadromy in a second sample of individuals with a moderate level of...
It is no secret that rivers have become one of our most important and imperiled resources around the globe. Guidance on how to manage rivers is urgently needed. Thankfully, a new book written by Dr. Angela Arthington: “Environmental Flows: Saving Rivers in the Third Millenium” takes a detailed look at rivers and how we can understand, manage, and restore them. This book is a very broad and comprehensive overview, organized into a series of 22 relatively concise chapters, beginning with an overview of the value of rivers and their current state of imperilment. This chapter sets the stage for understanding the range and magnitude of the challenges we face in saving rivers. For the purposes of this review, I partitioned...
Alternative male phenotypes in salmonine fishes arise from individuals that mature as larger and older anadromous marine-migrants or as smaller and younger freshwater residents. To better understand the processes influencing the expression of these phenotypes we examined the influences of growth in length (fork length) and whole body lipid content in rainbow trout (Oncorhynchus mykiss). Fish were sampled from the John Day River basin in northeast Oregon where both anadromous ("steelhead") and freshwater resident rainbow trout coexist. Larger males with higher lipid levels had a greater probability of maturing as a resident at age-1+. Among males, 38% were maturing overall, and the odds ratios of the logistic model...

    map background search result map search result map Variability in expression of anadromy by female <i>Oncorhynchus mykiss</i> within a river network Variability in expression of anadromy by female <i>Oncorhynchus mykiss</i> within a river network