Blood chemistry and swimming activity of rainbow trout exposed to supercooling and frazil ice

RICHARD S. BROWN; JULIE C. BRODEUR; GEOFF POWER; STEVEN F. DALY; KAREN D. WHITE; R. SCOTT MCKINLEY

Winnipeg, Manitoba, Canada

Workshop; 10th Workshop on River Ice; 1999

Adult and juvenile rainbow trout (Oncorhynchus mykiss) were exposed to supercooled temperatures, frazil ice, and anchor ice in a refrigerated flume.  The blood chemistry of the fish was measured before and after they were exposed to a frazil ice event.  Plasma chloride, sodium and potassium levels were significantly reduced in juvenile rainbow trout after 6.5 h of exposure to supercooling, frazil ice and anchor ice.  Plasma lactate did not vary but plasma glucose was increased although not in a statistically significant manner.  Blood parameters of adult fish varied in a similar way as in juveniles but none of the changes were statistically significant.  The swimming activity of half of the adult fish (measured by electromyogram telemetry) was significantly lower while exposed to frazil and anchor ice, and none were more active.  This reduction in activity may increase the likelihood of avian or mammalian predation during subsurface ice events.  These sublethal effects observed during exposure to supercooling and frazil ice suggest that further research is needed to determine how such events might impair fish survival.