Salmonid redd dewatering: What do we know
Dewatering of salmonid spawning areas causes abrupt changes in the intergravel environment that may lead to extensive losses of development phases while intergravel in redds. Information on tolerance to dewatering and the extent of physicochemical changes in the gravel during dewatering can be used to assess potential impacts and to design and implement effective mitigation methods. Studies with fall chinook salmon are summarized, and the comparisons are made with results from available literature. Potentially useful methods of mitigation are mentioned. We found that prehatch phases (cleavage eggs and embryos) can be dewatered for several successive days and survive, but posthatch phases (eleutheroembryos and alevins) usually die within 24 hours. Survival of prehatch phases during extended dewatering requires maintenance of favorable intergravel temperature and moisture levels. Elevated temperatures (up to 22/sup 0/C) can be tolerated for up to 8 hours without direct adverse effects, but freezing temperatures (/sup -/1.0/sup 0/C or below) are lethal. Dewatered gravels must remain sufficient moisture to provide near 100% humidity for egg and embryo survival. In field situations, physicochemical conditions that limit survival in dewatered gravels include residual flow, temperature, gravel size and composition, and dissolved oxygen. Biological variables such as alevin behavior and certain species characteristics also influence survival. 29 refs., 6 figs.
- Research Organization:
- Pacific Northwest Labs., Richland, WA (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 5349509
- Report Number(s):
- PNL-SA-11841; ON: DE85017905
- Country of Publication:
- United States
- Language:
- English
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