“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
Abstract
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