Salmon population in watersheds of different complexities following ice recession in Glacier Bay as determined by the physical habitat template

• Main Author: Sønderland, Svein Harald
• Other Authors: Milner, Alexander (Sandy), Ledger, Mark, na
• Format: Thesis
• Language: English
• Published: 2017
• Subjects: GB Physical geography; GE Environmental Sciences; Glacier Bay; Varden; glacier; Alaska
• Online Access: http://etheses.bham.ac.uk//id/eprint/7541/2.hassmallThumbnailVersion/S%C3%B8nderland17PhD.pdf; http://etheses.bham.ac.uk//id/eprint/7541/; http://etheses.bham.ac.uk//id/eprint/7541/2/S%C3%B8nderland17PhD.pdf

The diets of sympatric stream dwelling juvenile coho salmon (Oncorhynchus kisutch) and Dolly Varden (Salvelinus malma) were analyzed in five streams of different age and watershed complexity since glacial retreat in Glacier Bay, southeast Alaska. Interferometric synthetic aperture radar (IFSAR) data were analyzed with geographic information systems (GRASS GIS) to understand watershed change since deglaciation. Spatiotemporal variations of watershed characteristics from GIS were then used to develop a four-dimensional physical habitat template (PHT) and a directional model of stream development. Juvenile coho salmon and Dolly Varden coexisted in all streams with a strong overlap in diet while using different foraging zones. Diet niche breadth for both species increased with the amount of terrestrial insects in the diet as a result of resource depression, as mean fork length (FL) of juvenile fish increased when aquatic insects were a greater part of the diet, but decreased with greater terrestrial input. Using the stable isotopes of δ15N and δ13C, the contribution of marine derived nutrients (MDN) to stream biota was found to be determined by salmon spawner abundance and watershed retention, and an increase in δ15N and δ13C dispersion (SD) was found with stream age, likely causing a difference in the fractioning of δ15N and δ13C. The most significant change with stream age was denudation of watersheds and the development of stream networks. Dietary overlap was linked to fish resource depression, and controlled by stream geomorphology. Juvenile salmonids were found to consume sea lice (Lepeophtheirus salmonis) in the older streams.