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 3 min 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; Δ calculated as: [(time (s) after/time (s) before) − 1] × 100%), and so IR was used for further experiments. Physiologically, following skin extract exposure, plasma cortisol concentration was increased at 0.5 h (58.1 ± 14.6 ng/ml versus 4.32 ± 1.31 ng/ml, exposed versus control), hematocrit (Hct) was increased at 2 h (50.4 ± 1.0% versus 41.7 ± 1.6%), and leucocrit (Lct) was decreased at 0.5 and 2 h (0.534 ± 0.114 and 0.13 ± 0.01% versus 1.23 ± 0.20%). After 0.5 h exposures to 0, 1, 10 and 100 μg/l IPBC and skin extract, the time spent dashing (>5 cm/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 1 μg/l IPBC exposures (11.0 ± 3.0% and 17.7 ± 11.0%, respectively), but was absent after 10 μg/l and decreased after 100 μg/l IPBC. Physiologically, Hct and plasma lactate concentration were significantly increased above controls after 1 μg/l IPBC exposure (Hct: 45.7 ± 1.6% versus 34.0 ± 1.6%, lactate: 12.8 ± 1.2 mM versus 3.30 ± 1.2 mM). After 10 μg/l exposure, IPBC alone elicited a stress response similar to skin extract. However in the 100 μg/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 ≥1 μg/l IPBC.