ACUTE EFFECTS OF CHLORINATED RESIN ACID EXPOSURE ON JUVENILE RAINBOW-TROUT, ONCORHYNCHUS-MYKISS

The effects of an acute exposure to either 14-monochlorodehydroabietic acid (MCDHAA) or 12,14-dichlorodehydroabietic acid (DCDHAA) were exam ined in juvenile rainbow trout, Oncorhynchus mykiss. The experimentall y determined 96-h LC50 values (and their 95% confidence limits) were 1 .03 (0.72, 1.48) and 0.91 (0.70, 1.21) mg/L, for MCDHAA and DCDHAA, re spectively. To measure effects on several biochemical parameters, swim ming performance, and disease resistance, juvenile trout were exposed for 24 h to sublethal concentrations of one or the other resin acid in an intermittent-flow respirometer. Hematocrit, plasma lactate, and li ver protein were significantly affected by exposure to the highest dos e (80% of the 96-h LC50 value) of either of the resin acids. Plasma co rtisol levels were 14- and 3-fold higher than were controls. Resistanc e to infection by Aeromonas salmonicida was significantly reduced; the cumulative percent mortalities due to furunculosis in fish exposed to MCDHAA or DCDHAA reached 20 and 26%, respectively. Swimming performan ce, measured as critical swimming speed (mean values 6.32 +/- 0.20 and 5.93 +/- 0.15 body lengths per second for MCDHAA and DCDHAA, respecti vely), was not significantly affected by resin acid exposure.