Effects of dewatering on Chinook salmon redds: Tolerance of four developmental phases to daily dewaterings
chinook, salmon, eggs, survival
Journal or Book Title
Transactions of the American Fisheries Society
Four intergravel developmental phases of Chinook salmon (Oncorhynchustshawytscha) were dewatered experimentally in artificial redds. The redds consisted of aquariacontaining a gravel mix and supplied with 4 liters of water per minute at 10 C. Cleavage eggs andembryos (the egg phases), and eleutheroembryos and pre-emergent alevins (the alevin phases)were dewatered 20 consecutive times in 22-day tests. The egg phases were considerably moretolerant than the alevins. Some cleavage eggs were killed by 12- and 16-hour daily dewaterings,but embryos survived up to 22-hour daily dewaterings. Embryos also tolerated extended, multiple dewaterings (over 60% survival for four consecutive 118-hour periods) and one-time, continuousdewatering for up to 12 consecutive days (over 80% survival). In contrast, about half theeleutheroembryos were killed by 4-hour daily dewaterings, and nearly all pre-emergent alevinswere killed by 1-hour daily dewaterings. Intergravel temperatures were affected by insolation andair temperature. Intergravel temperatures increased to lethal levels during dewatering of cleavageeggs in early fall, and limited their survival. Growth of egg phases from some females wasretarded by dewatering, but this phenomenon was not consistent for all egg groups. The size ofsurviving eleutheroembryos decreased as the length of daily dewatering periods increased.