CHEMICAL PERCEPTION AND BEHAVIORAL-RESPONSE OF FRESH-WATER FISH TO 2-METHYLISOBORNEOL

The substance 2-methylisoborneol (MIB) often affects aquatic organisms and causes problem of off-flavours in fish. In order to know how fish become tainted with MIB, response and chemical sensitivity of three f reshwater fishes to MIB were examined behaviorally and electrophysiolo gically. The electrocardiographic tests showed that the threshold of d etection for this compound was 4.8 x 10(-5) ngl-l for the Nile tilapia and 2.1 x 10(-5) ngl(-1) for the rainbow trout. Fish whose olfactory rosettes were removed also showed the cardiac response to MIB, but the threshold increased by 3 and 5 orders of magnitude in the Nile tilapi a and rainbow trout respectively. The recordings of neural response of the olfactory tract of the carp to MIB solutions showed the olfactory threshold at a concentration of 4 x 10(-8) ngl(-1). In behavioral tes ts in tanks, MIB solutions did not attract these fishes and evoked no avoidance in these fishes. It was concluded that, while freshwater fis hes are extremely sensitive to MIB, they would not escape from waters contaminated with MIB and thus easily be tainted with MIB.