Survival of Brook and Brown Trout through the Spawning Season in a North Central Pennsylvania Watershed

Spawning is a critical time for stream-dwelling trout because of changes in physiological condition and behavior which may increase the risk of predation.  A radio telemetry study was conducted in a north central Pennsylvania watershed to assess survival during this critical period.  The study area consisted of a fourth order mainstem stream and four tributaries.  Fifty-five Brook Trout (Salvelinus fontinalis) and 49 Brown Trout (Salmo trutta) were tagged in mid-September 2012.  Kaplan-Meier estimates of survival were made and Cox proportional hazard models were used to examine covariate effects of fish size, stream order, and individual movement rates on survival.  Brook Trout survival was 60% ± 14% (±SE) through the end of the spawning season in mid-November.  However, survival after the spawning season was 91% ± 6% through January.  Brown Trout survival was higher than Brook Trout survival with 90% ± 5% surviving to mid-November and no mortality occurring after mid-November.  None of the covariates examined had a significant effect on survival.  These results provide a rare assessment of trout survival at a fine temporal scale and the difference in survival between species may be one mechanism responsible for the encroachment of non-native Brown Trout into native Brook Trout habitat.