Yearling Chinook Salmon Research Articles

Survival of Juvenile Chinook Salmon Challenged withRenibacterium salmoninarumand Administered Oral Doses of Erythromycin Thiocyanate for Different Durations

Abstract Erythromycin thiocyanate was administered orally at three daily dosages (50, 100, and 200 mg/kg body weight) for 7, 14, or 21 d to duplicate groups of yearling chinook salmon Oncorhynchus tshawytscha challenged with an intraperitoneal inoculation of kidney disease bacterium, Renibacterium salmoninarum. Two experiments were conducted sequentially to test the effects of the drug and bacterium challenge at 12 and 8°C. In each experiment, the number offish surviving at the end of the trial was significantly higher in tanks offish administered erythromycin, and survival was highest in tanks of fish administered the highest dosage of erythromycin for 21 d. In tests conducted at 12°C, mortality from bacterial kidney disease began much sooner than in tests conducted at 8°C. How long the drug was administered was a significant factor in tests conducted at both temperatures; survival increased in drug treatments of longer duration. Palatability of feed may be a complicating factor in determining the most a...

A microsporidium-induced lymphoblastosis in Chinook salmon Oncorhynchus tshawytscha in freshwater

Yearling chinook salmon Oncorhynchus tshawytscha were found to be infected with an intranuclear microsporidium. The primary pathologic response in infected salmon was a marked lymphoblastosis. Although clinical signs and gross pathology were similar to other salmonid fish health problems, the induced cellular changes and prominent nuclear inclusions permitted accurate differentiation and diagnosis. This is the first reported occurrence of this infection in freshwater

Precocial male maturation in laboratory-reared populations of chinook salmon, Oncorhynchus tshawytscha

The incidence of precocial male maturation in yearling chinook salmon, Oncorhynchus tshawytscha, was examined in four laboratory-reared populations. Slim Creek and Bowron River chinook salmon were about 4 weeks older than Harrison and Nanaimo river chinook salmon when sampled (14 vs. 13 months of age), but were also 20–40 g smaller. Approximately 29, 12, 0, and 0% of all males were precocious in Bowron River, Slim Creek, Harrison River, and Nanaimo River chinook salmon, respectively. Precocial male chinook salmon had gonadosomatic indices of about 5–6%, whereas immature salmon from all populations had indices under 1%. Precocial male chinook salmon were more robust bodied than immature salmon; precocial males had deeper bodies, deeper heads, and larger adipose fins. Variation among the study populations in the incidence of precocial male maturation may be related to differences among the populations in migration distance to the sea or in juvenile freshwater rearing life history. The chinook salmon would probably be a productive species with which to study the evolutionary ecology of precocial maturity in Pacific salmonids.

Susceptibility of Chinook Salmon Smolts to Bypass Systems at Hydroelectric Dams

Several hydroelectric dams in the Snake-Columbia river system are equipped with submersible traveling screens that project into the turbine intakes. The screens are designed to divert juvenile migrant Pacific salmon Oncorhynchus spp. and steelhead Salmo gairdneri from the intake upward into gatewells and the ajoining central bypass system. Assays ofgill Na+,K+-ATPase were performed on yearling chinook salmon O. tshawytscha collected during several routine fish guidance efficiency tests in 1985 and 1986. On three of the four sampling dates, gill Na+,K+-ATPase levels were significantly higher in fish guided into the gatewell than in those not guided. These data suggest there is a relationship between the physiological status of smolting yearling chinook salmon and their susceptibility to guidance by traveling screens. Assessments of salmonid out-migrations may be biased if they are based on samples from traveling-screen guidance systems.

Estimating the Daily Passage of Juvenile Salmonids at McNary Dam on the Columbia River

The U.S. National Marine Fisheries Service, under contract to the U.S. Army Corps of Engineers, monitored the seaward migration of juvenile salmonids through the Snake-Columbia river system from 1973 to 1983. We developed a procedure for estimating the numbers of steelhead Salmo gairdneri and yearling chinook salmon Oncorhynchus tshawytscha smolts passing McNary Dam each day in 1982-1983. The method utilized the fingerling collection and bypass system contained within the powerhouse. Freeze-branded groups of smolts released upstream from the dam were used to calibrate the efficiency with which migrants were collected over a range of powerhouse discharge levels. Application of collection efficiency calibration curves enables researchers and fisheries managers to generate daily estimates of smolt passage as a function of the amount of water discharged through the powerhouse and the number of fish collected in the bypass system.

Plasma thyroid hormones during smoltification of yearling and underyearling coho salmon and yearling chinook salmon and steelhead trout

Both yearling and underyearling (zero-age) coho salmon in fresh water showed spring- and/or summer increases in plasma thyroid hormone concentrations. The peak in plasma thyroxine (T 4) was larger and occurred earlier during the spring in yearling fish compared to zero-age fish. Both groups had similarly elevated plasma triiodothyronine (T 3) during the summer months. Groups of yearling and zero-age fish transferred serially to seawater net-pens showed differential rates of survival in seawater. In the zero-age fish, the greatest survival seemed coincident with the progression of the elevation of plasma T 3 in fish in fresh water. Success in seawater of yearling fish correlated with the progression of the plasma peak of T 4 in fish in fresh water. Peaks of thyroid hormones were also observed in chinook salmon and steelhead trout in fresh water. Although the survival of the chinook salmon in seawater net-pens was comparable to that of coho salmon, steelhead trout showed unexpectedly poor survival in seawater. These data suggest that analysis of changes in plasma thyroid hormones provides useful information regarding the optimal time to transfer coho salmon from fresh water to seawater. Whether this information can be applied in a similar manner to other species of salmonids requires further investigation.

Anesthetic and Handling Stress on Survival and Cortisol Concentration in Yearling Chinook Salmon (Oncorhynchus tshawytscha)

Brief anesthetization with 50 mg/L buffered MS-222® (ethyl m-aminobenzoate methanesulfonate) of yearling chinook salmon (Oncorhynchus tshawytscha) during mild handling caused no change in plasma cortisol concentrations compared with levels in non-anesthetized fish. Prolonged exposure (180 min) to a depressing dose of buffered MS-222® (25 mg/L) elevated cortisol more than an immobilizing dose (50 mg/L), while 100 mg/L was lethal within 30 min. Fish anesthetized (50 mg/L MS-222®) during a severe 30-min handling stress had significantly lower mortality than controls to a second handling stress applied when the fish were no longer anesthetized. Anesthetization during the first stressor also prevented the cortisol stress response evident in the control fish. Anesthetic (with or without buffer) administered before initial capture was most effective at increasing survival during a second stressor, while anesthetic supplied after initial capture may have been slightly less effective. A 0.5% NaCl solution supplied after capture was less effective than any anesthetic treatment in increasing future survival, but was better than no treatment. Saline treatment did not attenuate the cortisol stress response. A rapid method of plasma sample preparation for competitive protein binding assay of cortisol was developed. Key words: chinook salmon, cortisol, stress, anesthetic, cortisol assay, survival

Delayed Migrations of Yearling Chinook Salmon Since Completion of Lower Monumental and Little Goose Dams on the Snake River

Abstract Travel time for yearling chinook salmon (Oncorhynchus tshawytscha) to migrate the 370 km downstream from the Salmon River to Ice Harbor Dam was compared during 3 years prior (1966–68) and 4 years after (1970–74) impounding of the Snake River behind Lower Monumental and Little Goose dams. Prior to impounding, fish averaged 15 days of travel time to Ice Harbor Dam during low flows (1,000–2,000 m3/s) and 9 days during moderate flows (2,300–4,000 m3/s). After the new impoundments, average travel time was increased to 31 days in low flows and 20 days in moderate flows–a measured delay of 16 and 11 days, respectively.

Migration Rates of Yearling Chinook Salmon in Relation to Flows and Impoundments in the Columbia and Snake Rivers

Abstract Migration rates of yearling chinook salmon (Oncorhynchus tshawytscha) through free-flowing and impounded stretches of the Snake and Columbia Rivers were compared during periods of low and moderate river discharge. Generally, the rate of migration was directly related to the water flows; it was 21 km/day at the low river discharge (Columbia—4,248 m3/sec; Snake—1,416 m3/sec), and 37 km/day during moderate river discharge (Columbia—8,495 m3/sec; Snake—2,265 m3/sec). Migration rates through most free-flowing and impounded stretches of the Snake and Columbia Rivers were similar with the one exception that in McNary Reservoir (Columbia River) fish moved only about one-third as fast as elsewhere. Marked yearling chinook salmon from the Salmon River took 32 days to travel the 669 km to Bonneville Dam during the low river discharge in 1966. New impoundments may more than double the travel time now required during low river flows.

Iodine metabolism in young chinook salmon ( Oncorhynchus tschawytscha, Walbaum) : I. Thyroidal impairment with the use of 131I

Six monthly or six weekly injections of 100 μc 131I (as carrier-free iodide) (total dose 600 μc/fish) produced a profound impairment of thyroid function in yearling chinook salmon. Thyroid region 127I contents, radioiodine turnover studies, and modifications in iodinated metabolite contents, were the principal functional parameters examined. Histological examinations revealed that thyroid follicle destruction was not accompanied by an arrest of thyroxine synthesis. Preliminary microscopic and biochemical evidence also indicates that thyroid epithelial cell integrity is not a condition essential for thyroxine biosynthesis. At least 9 months after the disappearance of thyroid follicles detectable levels of thyroxine were produced. This amount appeared sufficient to maintain growth at a rate indistinguishable from that of controls. None of the peripheral changes described for young 131I-treated rainbow trout were observed in young chinook salmon in spite of highly significant decreases in thyroid region 127I. It was concluded that 131I destruction of functional thyroid elements is more difficult to achieve in the yearling chinook salmon than in the rainbow trout of the same age.