Charlie E. Smith

Effects on Rainbow Trout Fry of a Metals-Contaminated Diet of Benthic Invertebrates from the Clark Fork River, Montana

Abstract The upper Clark Fork River in northwestern Montana has received mining wastes from the Butte and Anaconda areas since 1880. These wastes have contaminated areas of the river bed and floodplain with tailings and heavy metal sludge, resulting in elevated concentration of metals in surface water, sediments, and biota. Rainbow trout Oncorhynchus mykiss were exposed immediately after hatching for 91 d to cadmium, copper, lead, and zinc in water at concentrations simulating those in Clark Fork River. From exogenous feeding (21 d posthatch) through 91 d, fry were also fed benthic invertebrates from the Clark Fork River that contained elevated concentrations of arsenic, cadmium, copper, and lead. Evaluations of different combinations of diet and water exposure indicated diet-borne metals were more important than water-borne metals – at the concentrations we tested – in reducing survival and growth of rainbow trout. Whole-body metal concentrations (μg/g, wet weight) at 91 d in fish fed Clark Fork inverteb...

The Controversy about Salmon Hatcheries

Abstract The use of hatcheries has been a subject of lengthy debate in the management of salmon and trout resources in the Pacific Northwest. The problem has resulted in part from the wide distribution of hatchery fish in circumstances where natural populations were disadvantaged by management policy involving hatchery fish and the confusion of the effects of management with the effects of artificial propagation. Recently, the controversy has been epitomized by the recommendations to fisheries management agencies that excess hatchery fish should not be allowed to spawn in the wild, and hatchery fish should be excluded from salmon populations listed under the Endangered Species Act. The authors of the present article disagree with those recommendations and conclude that hatchery fish have an important role in recovery and supplementation of wild stocks. The present article is an attempt to help give balance to the discussion by providing a different perspective on hatchery fish and the literature pertainin...

Acute Toxicity of Ammonia and Nitrite to Cutthroat Trout Fry

Abstract The toxicity of ammonia and of nitrite was tested on cutthroat trout (Salmo clarki) fry (1-3 g) for periods up to a month in eight laboratory flow-through bioassays. Median lethal concentration (LC50) values for ammonia (mg/liter un-ionized NH3) were 0.5-0.8 for 96 hours, and 0.3-0.6 for 36 days. Nitrite LC50 values (mg/liter NO2-N) were 0.5-0.6 for 96 hours, and 0.4 for 36 days. Tissues of fish exposed for 29 days to 0.34 mg/liter un-ionized ammonia evidenced degenerative changes in gills, kidneys, and livers. Cutthroat trout fry are comparable to rainbow trout (Salmo gairdneri) fry in their susceptibility to acute toxicity from aqueous ammonia and nitrite.

Experimental Nitrite Toxicity in Rainbow Trout and Chinook Salmon

Abstract Two groups of 20 yearling rainbow trout were exposed continuously to inflowing water containing 0.15 and 0.55 mg/liter nitrite as nitrite nitrogen (NO2N), for 48 and 24 hr, respectively. Both groups developed methemoglobinemia but mortality occurred only at the highest concentration (55%). Salmon exposed to 0.50 mg/liter NO2N for 24 hr developed methemoglobinemia and suffered a 40% mortality. Fingerling trout were less sensitive to nitrite than yearlings.

Performance of rainbow trout and Snake River cutthroat trout reared in oxygen-supersaturated water

Rainbow trout, Oncorhynchus mykiss, reared in water containing oxygen at 180% or 94% of saturation for 125 days showed no difference in growth or feed conversion. Hematocrits were nominally reduced in fish held in the supersaturated oxygen environment, but increased within 35 days of returning the fish to water at 94% oxygen saturation. Mortality was not affected. Hemoglobin levels did not differ statistically between treatments by the end of the trial. Cutthroat trout, O. clarki, reared in 183%, 127% or 97% oxygen-supersaturated water for 91 days also showed no differences in growth or feed conversion. Hematocrits decreased nominally as dissolved oxygen was increased. There were no differences in mortality during handling or distribution stress tests. Results of these trials indicated that long-term culture in water saturated up to 183% oxygen has no adverse effect on growth or survival of these two species.

Chronic Toxicity of Ammonia to Fathead Minnows

Abstract Chronic effects of ammonia on the fathead minnow Pimephales promelas were studied in the laboratory in two flow-through tests, each test lasting approximately 1 year. Fish were exposed to five test concentrations over the range 0.07–0.96 mg/L un-ionized ammonia (NH3); the mean pH of the test water was 8.0, and the mean temperature was 24.2°C. The tests started with 3- to 5-d-old larvae that were reared to sexual maturity; progeny of these fish (F1 were reared until they were 60 d old. The 5% probability level was chosen to indicate significance. No effects were observed on growth or survival of parental fish at 0.44 mg/L NH3, or on egg production or viability at 0.37 mg/L, but effects on all of these were observed at 0.91 mg/L. Growth and survival of F1 larvae were not affected at 0.36 mg/L NH3, which was the highest concentration at which these were tested. Egg hatching success was not affected at 0.19 mg/L NH3, but was at 0.37 mg/L. Brain lesions were common in parental fish at all stages of de...

Effect of Diet Composition on Performance of Rainbow Trout Brood Stock during a Three-year Period

Abstract Brood stock rainbow trout (Salmo gairdneri) were fed diets low, intermediate, and high in energy and protein over a 3-year period. At the end of the study fish fed diets high in energy and protein weighed more and produced a greater number of larger eggs than did fish fed diets intermediate or low in energy and protein. The average total number of eggs produced by 3-year-old spawners were significantly less than that produced by either 4- or 5-year-old fish; numbers produced by the two older groups of fish did not differ. There was no significant difference in percentage of eyed eggs of 3-, 4-, or 5-year-old fish fed different diets; but the percentage of eggs that reached the eyed stage tended to decrease as age of the fish increased. Number of eggs produced per kilogram of body weight was greatest in 3-year-old fish fed a low-energy, low-protein diet; numbers did not differ between 4- and 5-year-old fish. No significant differences existed in weight of eggs per kilogram of body weight between f...

Cellular inflammatory response of rainbow trout to the protozoan parasite that causes proliferative kidney disease.

Abstract The cellular inflammatory response of rainbow trout Oncorhynchus mykiss (formerly Salmo gairdneri) to the myxozoan parasite PKX that causes proliferative kidney disease was investigated. The response was studied from 3 to 20 weeks after the fish were injected with infected kidney homogenate. Kidney samples were examined by light and electron microscopy. In contrast to most myxosporeans, PKX provoked a severe host response. Parasites were found in peritubular capillaries and sinusoids 3 weeks postinjection. The initial response to PKX was hemopoietic hyperplasia followed by a marked granulomatous nephritis that was resolved by termination of the study at 20 weeks postinjection. The macrophage was the predominant cell type involved in the inflammatory response to PKX. We presume that the macrophage effectively interrupts the development of PKX and eliminates the parasite from the host.

Effects of Dietary Clinoptilolite on Levels of Effluent Ammonia from Hatchery Coho Salmon

Abstract The addition of 5 and 10% clinoptilolite to the diet ofcultured coho salmon (Oncorhynchus kisutch) did not cause a significant reduction in effluent water ammonia concentrations compared to effluent water from fish fed control diets. Growth rate was not affected by the addition of clinoptilolite to diets.

Communications: Histopathology of Gas Bubble Disease in Juvenile Rainbow Trout

Abstract Tissues from rainbow trout (Salmo gairdneri) grossly demonstrating gas bubble disease were examined histologically. Gas emboli were observed in vessels of gill filaments, in postorbital hemorrhages, and the atrium, ventricle, and bulbus arteriosus of the heart. Emphysemas were apparent in the dermis, between the dermis and epidermis, and in areolar connective tissue of fins, gill arches, and in the roofs of mouths. Necrosis, inflammation, and plasma leakage were sometimes associated with emphysemas.