Brian J. Pyper

Across-Species Comparisons of Spatial Scales of Environmental Effects on Survival Rates of Northeast Pacific Salmon

Abstract We estimated the spatial scales of covariation in indices of spawner-to-recruit survival rates among 116 wild stocks of pink salmon Oncorhynchus gorbuscha, chum salmon O. keta, and sockeye salmon O. nerka. These data spanned roughly four decades and represented stocks from 15 geographical regions in Washington, British Columbia, and Alaska. For comparisons between pink and chum salmon, we found positive covariation in survival rates within regions and between certain adjacent regions (e.g., correlations between 0.3 and 0.7) but little covariation between stocks of distant regions (separated by 1,000 km or more). Our results indicate that, on average, shared environmental effects accounted for at least 36% of the variation in survival rates of nearby pink and chum salmon stocks but only 18% for stocks separated by about 500 km. By comparing these between-species patterns with within-species patterns, we conclude that differences in the geographical overlap of fish during the freshwater and early m...

Relationships between coastal ocean conditions and survival rates of northeast Pacific salmon at multiple lags

Abstract We tested the hypothesis that survival rates from spawners to recruits in Pacific salmon Oncorhynchus spp. are primarily related to coastal ocean conditions during migration to the sea and soon after. We correlated measures of survival rate in units of log e (recruits/spawner) for 110 stocks of pink salmon O. gorbuscha, chum salmon O. keta, and sockeye salmon O. nerka with regional-scale indices of coastal sea surface temperature, sea surface salinity, and upwelling as well as with a large-scale index of ocean climate. We examined correlations by month and at multiple lags spanning the periods of spawning, freshwater residence, and early ocean residence of salmon. Survival rates of all three salmon species were related to ocean temperatures just prior to, during, and after out-migration, which are indicative of the early marine conditions experienced by juvenile salmon. This is consistent with the hypothesis that the early marine period is critical to the survival of juvenile salmon. However, sur...

Spatial Covariation in Survival Rates of Northeast Pacific Chum Salmon

Abstract Using indices of survival rate (residuals from stock-recruitment relationships) across four decades, we examined the spatial patterns of covariation among 40 wild and 27 hatchery stocks of chum salmon Oncorhynchus keta from 15 geographical regions in Washington, British Columbia, and Alaska. We found strong evidence of positive covariation among spawner-to-recruit survival rates of wild stocks within regions and between certain adjacent regions (e.g., correlations from 0.3 to 0.7) but little evidence of covariation between stocks of distant regions (e.g., separated by 1,000 km or more). Similarly, for hatchery stocks from Washington, British Columbia, and southeast Alaska, positive covariation in the indices of fry-to-recruit survival rate occurred only within regions and between certain adjacent regions. These patterns suggest that important environmental processes affecting interannual variation in spawner-to-recruit survival rates of chum salmon operate at local or regional spatial scales rath...

Evidence of density- and size-dependent mortality in hatchery-reared juvenile white sturgeon (Acipenser transmontanus) in the Kootenai River.

We evaluated effects of stocking level and size-at-release on survival rates of hatchery-reared juvenile white sturgeon (Acipenser transmontanus) in the Kootenai River using Cormack-Jolly-Seber and related models implemented in Program MARK. A total of 119768 marked and unmarked hatchery juveniles were released from 1992 to 2006, of which 2938 passive integrated transponder (PIT)-tagged fish were subsequently recaptured. Annual survival rates of marked groups ranged from 0.01 to 0.84 (mean = 0.45) during the first year at large, from 0.48 to 1.0 (mean = 0.84) in the second year, and averaged 1.0 during all subsequent years. First year survival rates declined substantially in recent years, particu- larly for small fish (<25 cm fork length). Approximately 59% of the variation in first year survival was explained by a negative relationship with estimated juvenile abundance (linear regression, P < 0.01). Length-at-release of individuals ex- plained a substantial proportion of the within-year variation in survival during the first year at large. Our results provide strong evidence of density- and size-dependent mortality in hatchery-reared juvenile white sturgeon in the Kootenai River. Management actions that prioritize the release of fewer, larger-sized fish will likely improve first year survival rates and subsequent recruitment to the spawning-age population.

A Decision Analysis Framework for Comparing Experimental Designs of Projects to Enhance Pacific Salmon

Abstract Fisheries management agencies are involved in many activities to enhance Pacific salmon Oncorhynchus spp. Monitoring the performance of pilot projects before deciding whether or not to apply a particular method of enhancement on a wide scale will result in better investment decisions. However, the costs of such monitoring can be substantial. We developed a quantitative framework based on decision analysis to determine whether the expected value of the information obtained through monitoring exceeds the costs of obtaining it. We applied this framework to a hypothetical problem in which managers have a fixed budget for constructing groundwater-fed side channels for chum salmon O. keta and must choose how much, if any, of that budget to allocate to monitoring. We used this example to identify the conditions under which monitoring can generate positive net economic returns and the characteristics of experimental designs for monitoring that yield the greatest net value. The choice between monitoring a...

Tag Retention and Effects of Tagging on Movement of the Giant Red Sea Cucumber Parastichopus californicus

Abstract We examined tag retention and the effects of tagging on short-term movements of the giant red sea cucumber Parastichopus californicus. Retention rates were monitored for six different tag types (Floy banner FTSL-73, cinch FT-4C, fingerling FTF-69, garment, single T-bar FD-94, and the coded wire tag), which were applied to 30 individuals under laboratory conditions. The single T-bar and coded wire tag had the highest retention rates: 70% and 60% after 16 weeks, and 40% and 37% after 32 weeks. To assess the effects of tagging and handling on movement, a field study was conducted in Amalga Harbor, Alaska, in which giant red sea cucumbers were tagged with T-bar tags and monitored for 24 h. Tagged and handled animals moved significantly farther than control animals. The median (linear) distance moved by control animals over 24 h was 1.8 m (range, 0.2–4.2 m), whereas the median distance for tagged animals was 4.2 m (range, 0.4–22.7 m). Short-term behavior was affected by both tagging and handling; ther...