1202

• UCREFRP Catalog Number: 1202
• Author: Berry, C. R., Jr.
• Title: Effects of Cold Shock on Colorado Squawfish Larvae
• USFW Year: 1986.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

This graph indicates that for fish acclimated to 22 C, a lethal shock would be a
decrease to 8.5 C.
CONCLUSION
In conclusion, we feel that our data is sound, because our findings agree
with most of the literature that shows that some fish can tolerate 10-15 C
temperature decreases without marked mortality (Nickum 1966, Speakman and
Krenkel 1972, Coutant et al. 1974, Coutant 1977). Additionally, our findings
agree with observations made by Mr. Roger Hamman, U.S. Fish and Wildlife
Service, who has cultured squawfish at Willow Beach National Fish Hatchery and
Dexter National Fish Hatchery for several years (Hamman 1981; personal
communication, 1985). The behavioral changes that we noted were typical of
those of other fish. While the temperature differences found between the Yampa
and the Green rivers in 1984 were probably harmless, those reported by Miller et
al. (1984) could have caused behavioral changes that increased larvae mortality
and led to the disappearance of squawfish larvae in the Green River in 1983.
Acknowledgements
Funding for this project was provided by the U.S. Fish and Wildlife Service
(Contract Number 14-16-0009-1501-W05) and we appreciate the cooperation of USFWS
Biologists Harold Tyus, Rick Jones, Buddy Jensen,-and Don Archer. Ms. Vicki
Rosen conducted most lab experiments and presented the report at the Western
Division of the American Fisheries Society meeting.
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LITERATURE CITED
Allanson, B., A. Bok, and N. VanWyk. 1971. The influence of exposure to low
temperature of TilaRia mossambica Peters. II. Changes in serum
osmolarity, sodium, and chloride ion concentration. J. Fish Biol.
3:181-185.
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