Adult Coho Salmon Oncorhynchus Kisutch Research Articles

Patterns of River Discharge and Temperature Differentially Influence Migration and Spawn Timing for Coho Salmon in the Umpqua River Basin, Oregon

AbstractThe movement patterns of native migratory fishes may reflect different selection pressures in different environments that are associated with predictable patterns of temperature and discharge. Spatial and temporal variability in the movement patterns of adult Coho Salmon Oncorhynchus kisutch were explored with data that were collected from the Umpqua River basin, Oregon, focusing on two points in their return migration: (1) main‐stem midriver migration timing of adult Coho Salmon as they pass Winchester Dam, Oregon, and (2) adult spawn timing in tributary streams of the Smith River. Main‐stem migration of Coho Salmon as they pass Winchester Dam began 7 to 15 d after peak annual water temperature, when mean daily temperatures cooled to 18°C, but before the increases in discharge that are associated with autumn rains. Although migration timing appeared to be strongly related to river temperature, spawn timing of Coho Salmon in tributaries of the Smith River subbasin appeared to respond to a combination of both discharge and temperature thresholds. Spawning occurred after initial annual peak discharge events and when stream temperatures fell below a threshold of 12°C. These results directly inform water conservation and protection planning for environmental flow criteria and thermal ranges during migration and spawn timing of imperiled Coho Salmon in the Oregon Coast Range.

Handling, infectious agents and physiological condition influence survival and post-release behaviour in migratory adult coho salmon after experimental displacement.

For Pacific salmon captured and released by fisheries, post-release behaviour and survival may be influenced by their health and condition at time of capture. We sought to characterize the interactions between infectious agent burden, fish immune and stress physiology and fisheries stressors to investigate the potential for capture-mediated pathogen-induced mortality in adult coho salmon Oncorhynchus kisutch. We used radio-telemetry paired with high-throughput qPCR of non-lethal gill biopsies for infectious agents and host biomarkers from 200 tagged fish experimentally displaced and exposed to various experimental fisheries treatments (gill net entanglement, recreational angling and recreational angling with air exposure vs. non-sampled control). We characterized relationships among post-release behaviour and survival, infectious agent presence and loads, physiological parameters and transcription profiles of stress and immune genes. All infectious agents detected were endemic and in loads consistent with previous adult Pacific salmon monitoring. Individuals exposed to fisheries treatments were less likely to reach spawning habitat compared to controls, and handling duration independent of fisheries gear had a negative effect on survival. High infectious agent burden was associated with accelerated migration initiation post-release, revealing behavioural plasticity in response to deteriorating condition in this semelparous species. Prevalence and load of infectious agents increased post-migration as well as transcription signatures reflected changes in immune and stress profiles consistent with senescence. Results from this study further our understanding of factors associated with fisheries that increase risk of post-release mortality and characterize some physiological mechanisms that underpin migratory behaviour.

Coho salmon spawner mortality in western US urban watersheds: bioinfiltration prevents lethal storm water impacts.

Summary Adult coho salmon Oncorhynchus kisutch return each autumn to freshwater spawning habitats throughout western North America. The migration coincides with increasing seasonal rainfall, which in turn increases storm water run‐off, particularly in urban watersheds with extensive impervious land cover. Previous field assessments in urban stream networks have shown that adult coho are dying prematurely at high rates (>50%). Despite significant management concerns for the long‐term conservation of threatened wild coho populations, a causal role for toxic run‐off in the mortality syndrome has not been demonstrated.We exposed otherwise healthy coho spawners to: (i) artificial storm water containing mixtures of metals and petroleum hydrocarbons, at or above concentrations previously measured in urban run‐off; (ii) undiluted storm water collected from a high traffic volume urban arterial road (i.e. highway run‐off); and (iii) highway run‐off that was first pre‐treated via bioinfiltration through experimental soil columns to remove pollutants.We find that mixtures of metals and petroleum hydrocarbons – conventional toxic constituents in urban storm water – are not sufficient to cause the spawner mortality syndrome. By contrast, untreated highway run‐off collected during nine distinct storm events was universally lethal to adult coho relative to unexposed controls. Lastly, the mortality syndrome was prevented when highway run‐off was pretreated by soil infiltration, a conventional green storm water infrastructure technology.Our results are the first direct evidence that: (i) toxic run‐off is killing adult coho in urban watersheds, and (ii) inexpensive mitigation measures can improve water quality and promote salmon survival. Synthesis and applications. Coho salmon, an iconic species with exceptional economic and cultural significance, are an ecological sentinel for the harmful effects of untreated urban run‐off. Wild coho populations cannot withstand the high rates of mortality that are now regularly occurring in urban spawning habitats. Green storm water infrastructure or similar pollution prevention methods should be incorporated to the maximal extent practicable, at the watershed scale, for all future development and redevelopment projects, particularly those involving transportation infrastructure.

Lack of Effect on Embryo Mortality and Fry Growth from Adult Coho Salmon Subjected to Electronarcosis Prior to Spawning

AbstractThe use of electronarcosis as a fish immobilization technique has reemerged in recent years. Previous studies have investigated behavioral effects of the technique. But investigations of the physical and physiological effects on fish of electrical immobilization have focused on different electrical waveforms or higher power densities than are used for electronarcosis. This study was designed to determine whether there was a significant negative effect on embryo survival or fry growth among the progeny of adult Coho Salmon Oncorhynchus kisutch immobilized by electronarcosis prior to spawning as compared with being immobilized by tricaine methanesulfonate or not being immobilized at all (control). Embryo mortality in family lots ranged from 0.67% to 55.05%, with no statistically significant differences among the treatments and the control. There were significant differences in the size of fry from adults subjected to electronarcosis rather than the other two treatments, but in all cases the fry from adults treated with electronarcosis were larger. These findings support the continued use of electronarcosis as a fish immobilization technique.

The efficacy of field techniques for obtaining and storing blood samples from fishes

Prompted by the dramatic increase in the use of blood analyses in fisheries research and monitoring, this study investigated the efficacy of common field techniques for sampling and storing blood from fishes. Three questions were addressed: (1) Do blood samples taken via rapid caudal puncture (the 'grab-and-stab' technique) yield similar results for live v. sacrificed groups of fishes? (2) Do rapidly obtained caudal blood samples accurately represent blood properties of fishes prior to capture? (3) Does storage of whole blood in an ice slurry for a working day (8·5 h) modify the properties of the plasma? It was shown that haematocrit, plasma ions, metabolites, stress hormones and sex hormones of caudal blood samples were statistically similar when taken from live v. recently sacrificed groups of adult coho salmon Oncorhynchus kisutch. Moreover, this study confirmed by using paired blood samples from cannulated O. kisutch that blood acquired through the caudal puncture technique (mean ±s.e. 142 ± 26 s after capture) was representative of fish prior to capture. Long-term (8·5 h) cold storage of sockeye salmon Oncorhynchus nerka whole blood caused significant decreases in plasma potassium and chloride, and a significant increase in plasma glucose. Previous research has suggested that these changes largely result from net movements of ions and molecules between the plasma and erythrocytes, movements that can occur within minutes of storage. Thus, blood samples from fishes should be centrifuged as quickly as practicable in the field for separation of plasma and erythrocytes to prevent potentially misleading data.

The Effect of Hatchery Spawning Protocols on Coho Salmon Return Timing in the Cowlitz River, Washington

AbstractWe compared the pre‐ and posthatchery return times of adult coho salmon Oncorhynchus kisutch on the Cowlitz River, Washington, after 30 years of hatchery operation. In addition, at the Cowlitz Salmon Hatchery in fall 1998, 1999, and 2000, we differentially tagged juveniles for release in 1999, 2000, and 2001 that were produced from broodstock originating from early (August to mid‐October), middle (mid‐October through November), and late (December and thereafter) time arrival windows to determine the fidelity of adult return time distribution to the window of origin. We found that posthatchery mean and median coho salmon adult return times were delayed about 2 weeks compared with prehatchery conditions, that October–November returns increased from 46% to 81% after hatchery operation, that a mean of 57% of 3‐year‐old adult fish returned in the return time window of origin, and that many of the early‐ and late‐origin fish returned in the middle time period. A mean of 70.4% of 2‐year‐old jacks from all releases returned in the middle return window. Much of the increase in October–November returns was probably due to a hatchery production emphasis of the middle‐returning fish. We recommend that broodstock be accumulated at historically proportional rates with respect to run timing, which may require additional adult holding ponds at the hatchery.

Electrical Anesthesia for Immobilizing Adult Coho Salmon in Freshwater

Wild adult coho salmon Oncorhynchus kisutch, returning to spawn, were sampled in freshwater with a DC shocking basket. Electrical anesthesia briefly immobilized fish and expedited sampling without the adverse effects of tricaine methanesulfonate (MS-222) or the excessive handling associated with physical restraint. Coho salmon mortality attributed to the shocking basket was 0.2% at Yehring Creek and 4.2% at the Chilkoot Lake weir. This is the first reported freshwater application of electrical anesthesia for handling salmonids.