2012/07/30 by William P. Connor, Kenneth F. Tiffan · 1 citation
Environmental Science · #Fish Ecology and Management Studies #Aquatic Invertebrate Ecology and Behavior #Hydrology and Sediment Transport Processes
paper · doi:10.1080/00028487.2012.685121
Abstract Data collected on juvenile anadromous salmonids implanted with passive integrated transponder (PIT) tags are used in mark–recapture analyses to understand the factors affecting survival of fish estimated between rearing in riverine habitat and dam passage. We estimated parr‐to‐smolt survival of PIT‐tagged naturally produced subyearling fall Chinook salmon Oncorhynchus tshawytscha to examine the previously unexplored influences of environmental and biological conditions measured prior to reservoir entry. Mean (±SE) parr‐to‐smolt survival of the early migrating cohorts was 45.4 ± 6.3% ( n = 13) compared with 37.4 ± 4.7% ( n = 13) for later migrating cohorts. Annual mean parr‐to‐smolt survival differed widely across years ranging from a low of 9.6 ± 0.5% ( n = 2) in 2001 to a high of 81.7 ± 4.6% ( n = 2) in 1999. Parr growth prior to reservoir entry and reservoir velocity provided the most information on variability in parr‐to‐smolt survival ( N = 26, R 2 = 0.75, corrected Akaike's information criterion [AIC c ] = −5.01). We suggest that parr growth and reservoir velocity were directly proportional to parr‐to‐smolt survival because fast growth and downstream movement reduces the time when fish are vulnerable to predators. The effect of reservoir velocity comports with previous published studies and supports management efforts to increase reservoir velocity. Few if any published studies explicitly relate parr growth measured on individual fish to survival estimated for their cohorts in freshwater. This study provides empirical evidence that upholds the long‐held belief that any anthropogenic activity that reduces growth of juvenile salmonids during freshwater rearing has the potential to reduce their survival.