TITLE:
Thermal Tempering Does Not Impact Rainbow Trout and Brown Trout Survival
AUTHORS:
Nathan Huysman, Jill M. Voorhees, Eric Krebs, Michael E. Barnes
KEYWORDS:
Tempering, Rainbow Trout, Oncorhynchus mykiss, Brown Trout, Salmo trutta, Temperature
JOURNAL NAME:
Advances in Bioscience and Biotechnology,
Vol.11 No.7,
July
28,
2020
ABSTRACT: Hatchery-reared fish are frequently adjusted
(tempered) to the higher water temperatures present in the water bodies where
they are to be stocked. This study was undertaken to determine the necessity of
such tempering practices. This study used
rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo
trutta) reared at 11.2°C. The first two trials for each species were designed
to simultaneously determine the upper incipient lethal temperature and 100% lethal
temperature over a 14-day period. The third trial for each species evaluated
the effects of an exaggerated 12-hour tempering regime on fish survival after
placement in elevated water temperatures. After transfer from a water temperature
of 11.2°C, no rainbow trout survived at 26°C, and only 50%
survived at 25°C. No brown trout survived at 22°C and only 50%
at 20°C. Survival of rainbow trout was not improved by the 12-hour
tempering regime where water temperatures were slowly increased from 11.2°C
to either 25°C or 26°C. Similarly, tempering did not improve
brown trout survival at either 20°C or 22°C. These results
suggest that tempering is not needed when hatchery-reared trout are reared and
stocked at the water temperatures within the range of those used in this study.