Chum Oncorhynchus Keta Research Articles

Piscirickettsia salmonis shedding and tissue burden, and hematological responses during cohabitation infections in chum Oncorhynchus keta, pink O. gorbuscha and Atlantic salmon Salmo salar.

BackgroundSalmonid rickettsial septicemia is an emergent and geographically widespread disease of marine-farmed salmonids caused by infection with the water-borne bacterium Piscirickettsia salmonis. Very little is known about the route, timing, or magnitude of bacterial shedding from infected fish.Methodology/principal findingsA cohabitation challenge model was used to assess shedding from chum Oncorhynchus keta, pink O. gorbuscha and Atlantic salmon Salmo salar. Infections in donor fish were established by intraperitoneal injection of P. salmonis. Naïve recipients were cohabitated with donor fish after which cumulative percent morbidity and mortality (CMM) was monitored, and bacterial burdens in kidney and in tank water were measured by qPCR. All donor fish died with mean days-to-death (MDD) among species ranging from 17.5 to 23.9. Among recipients, CMM ranged from 42.7% to 77.8% and MDD ranged from 49.7 to 56.4. In each trial, two peaks of bacterial DNA concentrations in tank water closely aligned with the MDD values of donor and recipient fish. Bacterial tissue burden and shedding rate, and plasma physiological parameters were obtained from individual donors and recipients. Statistically significant positive correlations between the shedding rate and P. salmonis kidney burden were measured in donor pink and in donor and recipient chum salmon, but not in donor or recipient Atlantic salmon. In Atlantic salmon, there was a negative correlation between kidney bacterial burden and hematocrit, plasma Ca++ and Mg++ values, whereas in infected chum salmon the correlation was positive for Na+ and Cl- and negative for glucose.ConclusionsA dependency of bacterial shedding on species-specific patterns of pathogenesis was suggested. The coincidence of bacterial shedding with mortality will inform pathogen transmission models.

Species and population diversity in Pacific salmon fisheries underpin indigenous food security

Summary Indigenous people are considered to be among the most vulnerable to food insecurity and biodiversity loss. Biodiversity is cited as a key component of indigenous food security; however, quantitative examples of this linkage are limited. We examined how species and population diversity influence the food security of indigenous fisheries for Pacific salmon (Oncorhynchus species). We compared two dimensions of food security – catch stability (interannual variability) and access (season length) – across a salmon diversity gradient for 21 fisheries on the Fraser River, Canada, over 30 years, using linear regression models. We used population diversity proxies derived from a range of existing measures because population‐specific data were unavailable. While both population and species diversity were generally associated with higher catch stability and temporal access, population diversity had a stronger signal. Fisheries with access to high species diversity had up to 1·4 times more stable catch than predicted by the portfolio effect and up to 1·2 times longer fishing seasons than fisheries with access to fewer species. Fisheries with access to high population diversity had up to 3·8 times more stable catch and three times longer seasons than fisheries with access to fewer populations. Catch stability of Chinook Oncorhynchus tshawytscha and sockeye Oncorhynchus nerka fisheries was best explained by the number of populations and conservation units, respectively, that migrate past a fishery en route to spawning grounds. Similar population diversity metrics were important explanatory variables for season length of sockeye, pink Oncorhynchus gorbuscha, coho Oncorhynchus kisutch and chum Oncorhynchus keta fisheries. Synthesis and applications. We show an empirical example of how multiple scales of biodiversity support food security across a large watershed and suggest that protecting fine‐scale salmon diversity will help promote food security for indigenous people. The scales of environmental assessments need to match the scales of the socio‐ecological processes that will be affected by development. We illustrate that upstream projects that damage salmon habitat could degrade the food security of downstream indigenous fisheries, with implications to Canadian indigenous people and to watersheds around the world where migratory fishes support local fisheries.

Comparative transcriptomics of Atlantic Salmo salar, chum Oncorhynchus keta and pink salmon O. gorbuscha during infections with salmon lice Lepeophtheirus salmonis

BackgroundSalmon species vary in susceptibility to infections with the salmon louse (Lepeophtheirus salmonis). Comparing mechanisms underlying responses in susceptible and resistant species is important for estimating impacts of infections on wild salmon, selective breeding of farmed salmon, and expanding our knowledge of fish immune responses to ectoparasites. Herein we report three L. salmonis experimental infection trials of co-habited Atlantic Salmo salar, chum Oncorhynchus keta and pink salmon O. gorbuscha, profiling hematocrit, blood cortisol concentrations, and transcriptomic responses of the anterior kidney and skin to the infection.ResultsIn all trials, infection densities (lice per host weight (g)) were consistently highest on chum salmon, followed by Atlantic salmon, and lowest in pink salmon. At 43 days post-exposure, all lice had developed to motile stages, and infection density was uniformly low among species. Hematocrit was reduced in infected Atlantic and chum salmon, and cortisol was elevated in infected chum salmon. Systemic transcriptomic responses were profiled in all species and large differences in response functions were identified between Atlantic and Pacific (chum and pink) salmon. Pink and chum salmon up-regulated acute phase response genes, including complement and coagulation components, and down-regulated antiviral immune genes. The pink salmon response involved the largest and most diverse iron sequestration and homeostasis mechanisms. Pattern recognition receptors were up-regulated in all species but the active components were often species-specific. C-type lectin domain family 4 member M and acidic mammalian chitinase were specifically up-regulated in the resistant pink salmon.ConclusionsExperimental exposures consistently indicated increased susceptibility in chum and Atlantic salmon, and resistance in pink salmon, with differences in infection density occurring within the first three days of infection. Transcriptomic analysis suggested candidate resistance functions including local inflammation with cytokines, specific innate pattern recognition receptors, and iron homeostasis. Suppressed antiviral immunity in both susceptible and resistant species indicates the importance of future work investigating co-infections of viral pathogens and lice.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-200) contains supplementary material, which is available to authorized users.

Age‐related thermal habitat use by Pacific salmon Oncorhynchus spp.

Age-related thermal habitat use by sockeye Oncorhynchus nerka, chum Oncorhynchus keta and pink Oncorhynchus gorbuscha salmon was examined using trawl data obtained in spring in the North Pacific Ocean. Thermal habitat use differed by species and age. Larger and older fishes inhabited cooler areas, whereas smaller and younger fishes inhabited warmer areas.

Comparison of the spectral sensitivity of three species of juvenile salmonids

The spectral sensitivity of chum Oncorhynchus keta, pink Oncorhynchus gorbuscha and masu Oncorhynchus masou masou salmon was measured by the optomotor reaction index in monochromatic light of 400, 440, 480, 520, 560, 600 and 620 nm using an interference filter. The reaction rate of chum salmon was highest at 520 nm but the rates of pink and masu salmon were highest at 560 nm. In addition, a high reaction rate at 400 nm was also observed in masu salmon, suggesting that masu salmon are sensitive to ultraviolet light.

Composition changes in retinal pigments according to habitat of chum and pink salmon

Juvenile chum Oncorhynchus keta and pink Oncorhynchus gorbuscha salmon change the composition of their visual pigments when they move from coastal waters to offshore in the Okhotsk Sea. Levels of the visual pigment rhodopsin were found to be high on the coast, while porphyropsin levels were high in offshore waters in both species. These facts suggest visual function may be similar, allowing them to coexist in the same sea area.