Portland State University. Department of Biology
Kim H. Brown
Date of Award
Master of Science (M.S.) in Biology
1 online resource (vii, 47 pages)
Adult salmonid populations embarking on difficult migrations have evolved to store more somatic energy prior to river entry. While it is known that lipids are the primary fuel for endurance swimming in fish, uncertainty still surrounds how these mechanisms are utilized by juvenile fish during seaward migration. A key phase in salmonid migration is the preparatory season of feeding and growth before swimming downstream. During this period, juvenile fish build somatic fuel stores through dietary uptake. Intestinal microbiota of steelhead trout (Oncorhynchus mykiss) vary drastically across their geographic range, with significant differences in the coastal and inland subspecies' microbiota lipid metabolism, suggesting variation for host lipid absorption. Along the O. mykiss range there is a vast difference in migration difficulty experienced by individual populations. In order to investigate the relationship between migration difficulty and lipid storage in pre-migration juvenile steelhead in the Columbia River Basin, lateralis muscle (red, type I) lipid storage was assessed across hatchery stocks. Lipid storage was quantified using fluorescent microscopy and image analysis with FIJI (ImageJ). To date, no published studies have quantified fish lipid storage with these techniques. Inland juveniles' lipid stores increased significantly with migration difficulty and number of anticipated dam passages. While the coastal subspecies stocks had no significant change in lipid storage associated with migration difficulty, individuals had significantly higher lipid stores than inland fish and lower mean body condition. Taken together, there is evidence that smoltification timing may be an equally important factor in parr lipid storage. Results from this study characterize juvenile lipid storage pre-migration, and elicit new questions about how smoltification rates may be impacted by migratory transit time to marine feeding grounds.
Morse, Emily Jean, "Parr Going the Distance: How Migratory Difficulty Influences Red Muscle Lipid Storage in Juvenile Oncorhynchus mykiss" (2019). Dissertations and Theses. Paper 5173.