Meeting Abstract
Recent studies show that glucocorticoids (GCs) play an important role in mediating life-history trade-offs. For example, stress induced levels of GCs predict survival in both migrating and spawning Pacific salmon (Oncorhynchus spp). Yet, we still understand little about the overall functioning of the hypothalamus-pituitary-interrenal (HPI-) axis, responsible for GC release. While GC levels increase during migration, it is unclear if the HPI-axis is still functioning normally, or has become dysregulated. At present, little is known about negative feedback efficacy in spawning salmon, or how close to maximal interrenal production capacity the increase levels of GCs are. Interestingly, it is possible that a dysregulation of the HPI-axis, which would normally prevent individuals from mounting appropriate responses to further stressors, may be an important trade-off between survival and spawning in these fish. Especially since prolonged elevation of GCs has traditionally been associated with chronic stress, resulting in reduced reproductive success. In contrast, in salmon elevated GCs may be critical in providing the resources necessary for successful migration. This project aims at assessing HPI-axis functioning in spawning sockeye to further elucidate the role GCs and the HPI-axis play in the migration and reproductive success in a semelparous fish. Fish were caught as they arrived at the Gates Creek spawning channel at different times during the spawning season, to be able to assess both successful spawning as well as pre-spawn mortality. Once caught HPI-axis functioning was assessed fish were released into the channel, where spawning behavior and success were obtained.
