UBC Theses and Dissertations
Validating the use of non-invasive energy sampling techniques to differentiate wild and enhanced Skeena sockeye salmon (Oncorhunchus nerka) populations Wale, Taylor
Sockeye salmon (Oncorhynchus nerka) is a key species to nearly every community existing within the Skeena River Watershed. Spawning enhancement programs within the Babine sub-watershed have enabled two sockeye populations at Pinkut Creek and Fulton River to increase in abundance over several decades and now comprise the majority (> 75%) of the Skeena River sockeye aggregate stock, amidst a long-term decline for wild populations. Mixed-stock harvests without means to differentiate wild from enhanced populations have contributed to overexploitation of wild sockeye populations. This study used a microwave energy meter (Distell Fat Meter, Model FFM 692) to examine if populations could be differentiated based on energy reserves. At a full-span, salmon counting fence located along the migration route of Lake Babine sockeye populations, I externally tagged and assessed energy status of 2,056 sockeye, using tag recoveries (n = 252) on spawning grounds to infer population identification. I found that the energy meter was able to differentiate enhanced Babine sockeye (pooled between the two enhanced populations) from wild Babine sockeye (all wild populations pooled; Mann-Whitney U-test; P < 0.001). An established model from Crossin and Hinch (2005) was used to estimate gross somatic energy (GSE) from energy meter readings and enabled the comparison of this metric among populations. Previous literature has suggested that energy stores will be the highest among populations with the longest remaining migration distance at the time of sampling, but I did not find this to be the case. The two enhanced populations had higher GSE than wild populations despite not having the longest migration distance remaining following sampling. The results of my thesis have begun to validate the use of the energy meter to differentiate wild and enhanced sockeye within the Skeena River system and have the potential to contribute to and inform a shift towards more sustainable terminal, known-stock fishing practices. Finally, my tagging results enabled a re-examination of the run timing of wild and enhanced populations as they enter the Lake Babine system which has not been examined for several decades and is important information for considering and strategizing sustainable terminal fisheries in this system.
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