Effects of Dewatering on Chinook Salmon Redds: Tolerance of Four Developmental Phases to Daily Dewaterings

Abstract

Four intergravel developmental phases of chinook salmon Oncorhynchus tshawytscha were dewatered experimentally in artificial redds. The redds consisted of aquaria containing a gravel mix and supplied with 4 liters of water per minute at 10 C. Cleavage eggs and embryos (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 more tolerant 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, continuous dewatering for up to 12 consecutive days (over 80% survival). In contrast, about half the eleutheroembryos were killed by 4‐hour daily dewaterings, and nearly all pre‐emergent alevins were killed by 1‐hour daily dewaterings. Intergravel temperatures were affected by insolation and air temperature. Intergravel temperatures increased to lethal levels during dewatering of cleavage eggs in early fall, and limited their survival. Growth of egg phases from some females was retarded by dewatering, but this phenomenon was not consistent for all egg groups. The size of surviving eleutheroembryos decreased as the length of daily dewatering periods increased.

Hydropower-related pulsed-flow impacts on stream fishes: a brief review, conceptual model, knowledge gaps, and research needs

“…Stranding can be classified into two categories: beach stranding, when fish flounder out of the water on the substrate; and entrapment, when fish are isolated in pockets of water (e.g., in potholes) with no access to the free-flowing surface water (Higgins and Bradford 1996;Hoffarth 2004;Hunter 1992). Stranding has been observed in several field studies (e.g., Bauersfeld 1978;Hamilton and Buell 1976;Olson and Metzgar 1987) and can result in desiccation, temperature stress, hypoxia, predation, and mortality of fish eggs, fry, juvenile, and sometimes adult fish (e.g., Becker et al 1982;Hoffarth 2004;Hunter 1992) with consequent impacts on fish populations. Becker et al (1982) observed that eggs and fry were most vulnerable to high temperature stress when temperature rose to 20-25°C from an ambient river temperature of 6°C.…”

“…Stranding has been observed in several field studies (e.g., Bauersfeld 1978;Hamilton and Buell 1976;Olson and Metzgar 1987) and can result in desiccation, temperature stress, hypoxia, predation, and mortality of fish eggs, fry, juvenile, and sometimes adult fish (e.g., Becker et al 1982;Hoffarth 2004;Hunter 1992) with consequent impacts on fish populations. Becker et al (1982) observed that eggs and fry were most vulnerable to high temperature stress when temperature rose to 20-25°C from an ambient river temperature of 6°C. Although some eggs can survive stranding if kept moist at appropriate temperatures, alevins are more vulnerable because they cannot Fig.…”

Survival of eggs of Atlantic salmon (Salmo salar) in a drawdown zone of a regulated river influenced by groundwater

“…The extent and duration of flow alteration and the stage of 40 development will influence the survival, and newly hatched alevins are less tolerant ; 41 . If not subjected to extreme temperatures (in this case warm water) or predation, 42 laboratory studies have confirmed that salmonid eggs may survive for weeks in dewatered gravel if they are kept 43 moisty (Becker et al, 1982;Reiser & White, 1983). The aim of our study was to 44 investigate the survival of Atlantic salmon eggs in a large area of potential spawning grounds that is permanently 45 dewatered during most of the egg incubation period due to regulation.…”

The relationship between genetic variation and fitness in chinook salmon, Oncorhynchus tshawytscha (Walbaum): Implications for aquaculture and evolutionary theory.

“…W ater temperature was monitored with a data logger (Onset Computer Corp., Pocasset, MA) to allow for an accurate calculation of accumulated temperature units (ATUs), a standard descriptor for early developmental stages in fish. One temperature unit equals the number of degrees Celsius (above freezing) for a period of 24 hours (Becker et al 1982).…”

“…This is a modification of a standard hatchery practice used to identify and remove unfertilized eggs (e.g., Leitritz and Lewis 1980 Alevins were transferred ('ponded') to rearing tanks January 29-30, 1998 (892-911 ATUs). Ponding time was determined based on elapsed ATUs (Becker et al 1982) and the physical appearance of the alevins (degree of yolk sac absorption). Ponding is timed to coincide with the commencement of exogenous feeding.…”