Acclimation in Simulated Lake Water Increases Survival of Lahontan Cutthroat Trout Challenged with Saline, Alkaline Water from Walker Lake, Nevada

Abstract

AbstractWe investigated the effect of acclimation and condition factor (K) on short‐term survival of subyearling Lahontan cutthroat trout Oncorhynchus clarkii henshawi reared at Lahontan National Fish Hatchery, Gardnerville, Nevada, and challenged for 1 week with saline, alkaline water from Walker Lake, Nevada. The effect of acclimation and lake‐water challenge on plasma osmolality was also investigated. Fish were acclimated for 0, 8, or 17 d in simulated lake water with gradual and simultaneous increases in total dissolved solids and pH. Mean (±SE) survival rates (proportion) during three replicate, weeklong challenges in Walker Lake water for the 0‐, 8‐, and 17‐d acclimation groups were 0.153 ± 0.0409, 0.236 ± 0.0371, and 0.487 ± 0.1040, respectively. During all three challenge replicates, fish acclimated for 17 d experienced a lower hazard of death than unacclimated fish; fish in the 0‐ and 8‐d acclimation groups survived at similar rates. Higher K‐values were associated with a lower hazard of death during all three replicate challenges. Greater K was correlated with longer fork length (FL). For the 8‐d acclimation treatment group, the proportion of fish surviving the challenge was higher when K and FL were both greater than median values. In the 17‐d acclimation treatment, fish with either higher K‐values or longer FLs survived at higher rates than did smaller, thinner fish. Regardless of acclimation duration, postchallenge plasma osmolality was higher than the baseline level for fish that did not survive the challenge. Challenge survivors acclimated for 17 d exhibited lower plasma osmolalities than fish that did not survive, and plasma osmolalities in survivors were similar to baseline levels. Our results indicate short‐term survival rates for Lahontan cutthroat trout raised at the Lahontan National Fish Hatchery and stocked in Walker Lake may be improved by lengthy acclimation in simulated lake water and by stocking fish of higher K or longer length.