The effects of fluctuating diel temperature cycles on survival, growth, plasma cortisol and glucose concentrations, liver weight, and liver glycogen of juvenile coho salmon Oncorhynchus kisutch were determined. Temperature cycles (10-13', 9-15', 8-17 ø, and 6.5-20øC) were selected to simulate observed temperatures in clear-cuts of southeastern Alaska. Different levels of feeding, including starvation, were used in each of the tests. LT50s (peak temperature within a cycle producing 50% mortality) were 28øC for age-0 fish (350 mg) and 26'12 for age-II fish (22-g presmolts). Cyclic temperatures for 40 d, averaging 1 loc daily, did not influence growth of age-0 fish on any food ration as compared to controls held at a constant 1 IøC. Plasma cortisol and glucose concentrations were significantly greater in fish maintained for 20 d in the 6.5-20øC cycle but not different in fish in 10-13 ø and 9-150C cycles or a constant 11øC. These elevated concentrations may be indicators of long-term stress. Plasma cortisol concentrations were lower in starved fish than in fed fish at all temperature regimes; however, fluctuating temperature did not enhance starvation effects on cortisol levels. Diel temperature cycles did not affect liver weights or liver glycogen concentrations.
The sensitivity of various species and life stages of Alaskan freshwater and anadromous fishes to benzene and the water‐soluble fraction of Prudhoe Bay crude oil was determined with 96‐hour toxicity tests. Freshwater juveniles of the six salmonid species tested had similar sensitivities. Median tolerance limits (TLmˈs) of these salmonids for crude oil ranged from 2.7 to 4.4 mg/liter; TLmˈs of benzene ranged from 11.7 to 14.7 μl/liter. Threespine sticklebacks and, to a lesser extent, slimy sculpins were more tolerant than salmonids and had larger TLmˈs: Threespine sticklebacks had a crude‐oil TLm of 10.4 mg/liter and a benzene TLm of 24.8 μl/liter; slimy sculpins had a crude‐oil TLm of 6.44 mg/liter and a benzene TLm of 15.4 μl/liter. Eggs of pink salmon and coho salmon were quite tolerant to crude oil (TLm > 12 mg/liter) and benzene (TLm = 339–542 μl/liter). Emergent fry were the most sensitive freshwater stage (crude‐oil TLm = 8.0 mg/liter; benzene TLm = 12.3–17.1 μl/liter). Out‐migrant salmonids tested in seawater were twice as sensitive as out‐migrant salmonids tested in fresh water, apparently because of the additional stress of entering seawater and the physiological changes associated with this transition. Freshwater TLmˈs were 2.3–8.0 mg/liter for crude oil and 10.8–17.1 μl/liter for benzene. Corresponding seawater sensitivities were 1.1–3.6 mg/liter for crude oil and 5.5–8.5 μl/liter for benzene.
Coho salmon, Oncorhynchus kisutch, fry were exposed for 40 days to stable, sublethal concentrations of toluene (0.4, 0.8, 1.6, 3.2, 5.8 •l/liter) and naphthalene (0.2, 0.4, 0.7, 1.4 rag/liter) in fresh water. All fry were fed equal daily rations of Oregon Moist Pellet Formula If. Dry weights, wet weights, and lengths of fry exposed to the two highest concentrations of each toxicant for 40 days were significantly less than controls (P • 0.01). Growth per day, determined from weights and lengths, decreased linearly with increased concentrations. Fry exposed to naphthalene had a slower growth rate than fry exposed to equivalent concentrations (percentage of the 96-hour median lethal concentration or LC50) of toluene. Concentrations 18% of the LC50 of naphthalene and 26% of the LC50 of toluene had no effect on dry weight, wet weight, or length of exposed fry.
A metering device was developed to introduce benzene, toluene, xylene, and 1,2,4 trimethylbenzene vapors into water using air as a carrier gas. Setting the carrier gas flows for the respective aromatics at 10, 25, 120, and 500 cm3/min for 2 h resulted in concentrations of 8.2, 13.0, 12.0, and 7.2 μl/liter, respectively, in 4 liters of water. The aromatic concentrations were maintained in a static system by bubbling air through the water, and in a continuous flow system by replenishing the water. In static systems the respective aromatic concentrations were maintained for 4 days within the ranges of 13–14, 5.1–7.0, 0.40–0.50, and 0.018–0.028 μl/liter by bubbling the aromatics into the water at 5 cm3/min and independently aerating the water at 100 cm3/min. In a 14-day continuous flow system benzene concentrations ranged from 2.1–2.8 μl/liter when benzene was bubbling at 23 cm3/min and water was flowing at 1.8 liters/min.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.