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Evaluating Laboratory‐Derived Thermal Criteria in the Field: An Example Involving Bonneville Cutthroat Trout
Author(s) -
Schrank Amy J.,
Rahel Frank J.,
Johnstone Helene C.
Publication year - 2003
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(2003)132<0100:eldtci>2.0.co;2
Subject(s) - trout , electrofishing , oncorhynchus , environmental science , limiting , diel vertical migration , rainbow trout , fish <actinopterygii> , fishery , abundance (ecology) , fontinalis , ecology , biology , salvelinus , engineering , mechanical engineering
Water temperature plays an important role in limiting salmonid distributions, and there is much interest in applying laboratory‐derived thermal tolerance limits to field conditions. We examined the response of Bonneville cutthroat trout Oncorhynchus clarki utah to stream thermal regimes expected to be harmful based on laboratory thermal tolerance tests. We monitored water temperature throughout the summer concurrently with trout abundance and movement in a Rocky Mountain stream. Fish abundance at two sites was estimated with three‐pass depletion electrofishing before, during, and after peak summer temperatures. Fish movement throughout the summer was examined with radio telemetry, a two‐way weir, and visible implant tags. We hypothesized that fish would emigrate or die as summer water temperatures increased beyond the 7‐d upper incipient lethal temperature (LT50) of 24.2°C determined from laboratory experiments. However, our results suggested that fish neither emigrated from warm stream reaches nor experienced mortality, despite the presence of maximum daily water temperatures as high as 27°C. Furthermore, we found no evidence that fish resided in localized coolwater refuges. Large diel fluctuations of 10–13°C resulted in cool nighttime temperatures that presumably allowed trout to survive despite 2–5 weeks of daily exposure to temperatures exceeding the 7‐d LT50.