“Days after sockeye passed through extremely fast-moving water, we started to see fish dying only a short distance from their spawning grounds,” said Nicholas Burnett, a research biologist at UBC and lead author of the study, published in Physiological and Biochemical Zoology.
The key question here is whether these fish exhibit the Viral Signature that DFO scientist Kristy Miller has looked into. Fraser sockeye with the signature show high levels of disease morphology and exhibit as much as 90% mortality in some subcomponents of the Fraser run. This is known as pre-spawn mortality
Wild riverine fishes are known to rely on burst swimming to traverse hydraulically challenging reaches, and yet there has been little investigation as to whether swimming anaerobically in areas of high flow can lead to delayed mortality. Using acoustic accelerometer transmitters, we estimated the anaerobic activity of anadromous adult sockeye salmon (Oncorhynchus nerka) in the tailrace of a diversion dam in British Columbia, Canada, and its effects on the remaining 50 km of their freshwater spawning migration. Consistent with our hypothesis, migrants that elicited burst swimming behaviors in high flows were more likely to succumb to mortality following dam passage. Females swam with more anaerobic effort compared to males, providing a mechanism for the female-biased migration mortality observed in this watershed. Alterations to dam operations prevented the release of hypolimnetic water from an upstream lake, exposing some migrants to supraoptimal, near-lethal water temperatures (i.e., 24°C) that inhibited their ability to locate, enter, and ascend a vertical-slot fishway. Findings from this study have shown delayed post–dam passage survival consequences of high-flow-induced burst swimming in sockeye salmon. We highlight the need for studies to investigate whether dams can impose other carryover effects on wild aquatic animals.See: http://www.jstor.org/stable/10.1086/677219?Search=yes&resultItemClick=true&searchText=Nicholas&searchText=Burnett&searchUri=%2Faction%2FdoBasicSearch%3FQuery%3DNicholas%2BBurnett%26amp%3Bfilter%3Djid%253A10.2307%252Fj50000153%26amp%3BSearch%3DSearch%26amp%3Bwc%3Don%26amp%3Bfc%3Doff%26amp%3BglobalSearch%3D%26amp%3BsbbBox%3D%26amp%3BsbjBox%3D%26amp%3BsbpBox%3D