The alarm reaction of coho salmon parr is impaired by the carbamate fungicide IPBC.

To determine whether the carbamate fungicide IPBC alters the olfactory-mediated behavioral and physiologic alarm responses of coho salmon parr (Oncorhynchus kisutch), groups of coho were exposed to skin extract (an alarm pheromone source) under a variety of conditions. In the 3min following skin extract exposure, freezing behavior was significantly increased (In the 3 min following skin extract exposure, freezing behavior was significantly increased under darkness (IR lighting) but not ambient lighting (25.3+/-2.6% and 7.5+/-5.7%, respectively; Delta calculated as: [(time (s) after/time (s) before)-1]x100%), and so IR was used for further experiments. Physiologically, following skin extract exposure, plasma cortisol concentration was increased at 0.5h (58.1+/-14.6ng/ml versus 4.32+/-1.31ng/ml, exposed versus control), hematocrit (Hct) was increased at 2h (50.4+/-1.0% versus 41.7+/-1.6%), and leucocrit (Lct) was decreased at 0.5 and 2h (0.534+/-0.114 and 0.13+/-0.01% versus 1.23+/-0.20%). After 0.5h exposures to 0, 1, 10 and 100microg/l IPBC and skin extract, the time spent dashing (>5cm/s) increased significantly (323+/-118%) in the first minute after skin extract exposure, but was absent in IPBC-exposed coho. Freezing behavior increased after skin extract exposure with control and 1microg/l IPBC exposures (11.0+/-3.0% and 17.7+/-11.0%, respectively), but was absent after 10microg/l and decreased after 100microg/l IPBC. Physiologically, Hct and plasma lactate concentration were significantly increased above controls after 1microg/l IPBC exposure (Hct: 45.7+/-1.6% versus 34.0+/-1.6%, lactate: 12.8+/-1.2mM versus 3.30+/-1.2mM). After 10microg/l exposure, IPBC alone elicited a stress response similar to skin extract. However in the 100microg/l treatment group the stress parameters were not different from controls. These findings suggest that the behavioral and physiologic alarm responses of juvenile salmonids may be impaired by acute exposure to > or =1microg/l IPBC.