Renibacterium salmoninarum causes bacterial kidney disease (BKD), a chronic and sometimes fatal disease of salmon and trout that could lower fitness in populations with high prevalences of infection. Prevalence of R. salmoninarum infection among juvenile Chinook salmon Oncorhynchus tshawytscha inhabiting neritic marine habitats in North Puget Sound, Washington, USA, was assessed in 2002 and 2003. Fish were collected by monthly surface trawl at 32 sites within 4 bays, and kidney infections were detected by a quantitative fluorescent antibody technique (qFAT). The sensitivity of the qFAT was within an order of magnitude of the quantitative real-time PCR (qPCR) sensitivity. Prevalence of infection was classified by fish origin (marked/hatchery vs. unmarked/likely natural spawn), month of capture, capture location and stock origin. The highest percentages of infected fish (63.5 to 63.8%) and the greatest infection severity were observed for fish collected in Bellingham Bay. The lowest percentages were found in Skagit Bay (11.4 to 13.5%); however, there was no difference in prevalence between marked and unmarked fish among the capture locations. The optimal logistic regression model of infection probabilities identified the capture location of Bellingham Bay as the strongest effect, and analysis of coded wire tagged (CWT) fish revealed that prevalence of infection was associated with the capture location and not with the originating stock. These results suggest that infections can occur during the early marine life stages of Chinook salmon that may be due to common reservoirs of infection or horizontal transmission among fish stocks.

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Hatchery spring Chinook Salmon Oncorhynchus tshawytscha from Parkdale Hatchery on the Hood River, Oregon, and Carson National Fish Hatchery (CNFH) on the Wind River, Washington, were reared under a common‐garden experimental regime at CNFH over three consecutive brood years (2008–2010) to assess the effects of stock on smoltification and early male maturation. Rearing groups were monitored for size, percent solid (a surrogate for whole‐body lipid), gill Na+,K+‐ATPase activity, and rate of precocious maturation in males (i.e., age‐2 minijack rate). Despite rearing of the stocks under identical conditions, the out‐of‐basin Hood River stock was significantly smaller throughout the study and at release as smolts, had lower whole‐body lipid at release, and had lower gill Na+,K+‐ATPase activity at release than the Carson stock; furthermore, the Hood River stock exhibited much higher mean minijack rates than the Carson stock (45% versus 23% of males). Using logistic regression, we demonstrated that the threshold size for initiation of early male maturation was significantly lower for the Hood River stock than for the Carson stock, suggesting a genetic basis for this life history difference. The present study highlights the importance of understanding how specific genotypes may respond differently to the unique environmental conditions in a given hatchery environment. These differences may in turn influence physiological and life history pathways that affect smolt‐to‐adult return rates and the demography of returning adults.

We assessed the effects of rearing conditions in four hatchery programs from the upper Columbia River basin on the survival and demographics of yearling summer Chinook Salmon Oncorhynchus tshawytscha over four release years. Juveniles from each hatchery program were initially reared at Eastbank Hatchery near Wenatchee, Washington, (which uses groundwater for fish rearing) and experienced similar rearing temperatures until their first autumn in culture. Fish that were to be used for two of the programs were subsequently transferred to surface water acclimation sites, where they were reared until release the following spring (surface water winter rearing). Fish to be used for the other two programs were overwintered at the Eastbank Hatchery and then transferred to their acclimation and release sites 1 to 2 months before spring release (groundwater winter rearing). Fish from the two rearing strategies experienced contrasting temperature profiles, which in turn affected winter growth, age at maturation, and smolt-to-adult survival (SAS). Overall, the two release groups that were overwintered in colder surface water experienced reduced winter growth, reduced minijack rate, and smaller size at release, but achieved a two-to threefold higher SAS than did the two release groups overwintered in warmer groundwater at Eastbank Hatchery. In addition, based on migration data compiled from fish tagged with PIT tags, smaller juveniles tended to mature at older age-classes than did larger smolts. We concluded that rearing yearling hatchery summer Chinook Salmon under more natural thermal regimes (surface water) may result in the return of larger, older adults that have a higher survival rate than would fish reared under constant or less natural thermal regimes (ground water). These results highlight the importance of the hatchery-rearing environment in shaping the survival and life history of summer Chinook Salmon juveniles released into the Columbia River basin.

Traditionally, harmful algal bloom studies have primarily focused on quantifying toxin levels contained within the phytoplankton cells of interest. In the case of paralytic shellfish poisoning toxins (PSTs), intracellular toxin levels and the effects of dietary consumption of toxic cells by planktivores have been well documented. However, little information is available regarding the levels of extracellular PSTs that may leak or be released into seawater from toxic cells during blooms. In order to fully evaluate the risks of harmful algal bloom toxins in the marine food web, it is necessary to understand all potential routes of exposure. In the present study, extracellular and intracellular PST levels were measured in field seawater samples (collected weekly from June to October [2004][2005][2006][2007] and in Alexandrium spp. culture samples isolated from Sequim Bay, Washington. Measurable levels of intra-and extra-cellular toxins were detected in both field and culture samples via receptor binding assay (RBA) and an enzyme-linked immunosorbent assay (ELISA). Characterization of the PST toxin profile in the Sequim Bay isolates by pre- Mar. Drugs 2008, 6104 column oxidation and HPLC-fluorescence detection revealed that gonyautoxin 1 and 4 made up 65 ± 9.7 % of the total PSTs present. Collectively, these data confirm that extracellular PSTs are present during blooms of Alexandrium spp. in the Sequim Bay region.