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Effects of Fluctuating Temperature on Mortality, Stress, and Energy Reserves of Juvenile Coho Salmon
Author(s) -
Thomas Robert E.,
Gharrett Jessica A.,
Carls Mark G.,
Rice Stanley D.,
Moles Adam,
Korn Sid
Publication year - 1986
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1986)115<52:eoftom>2.0.co;2
Subject(s) - juvenile , oncorhynchus , diel vertical migration , glycogen , fish <actinopterygii> , starvation , biology , zoology , endocrinology , medicine , chemistry , fishery , ecology
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°, and 6.5–20°C) 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 28°C for age‐0 fish (350 mg) and 26°C for age‐II fish (22‐g presmolts). Cyclic temperatures for 40 d, averaging 11°C daily, did not influence growth of age‐0 fish on any food ration as compared to controls held at a constant 11°C. Plasma cortisol and glucose concentrations were significantly greater in fish maintained for 20 d in the 6.5–20°C cycle but not different in fish in 10–13° and 9–15°C cycles or a constant 11°C. 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.