INVESTIGATING ANTIPREDATOR BEHAVIOR IN 3 GENETICALLY DIFFERENTIATED POPULATIONS OF NONMIGRATORY GALAXIID FISHES IN A NEW-ZEALAND RIVER

Galaxias vulgaris Stokell, which has until now been considered a single widespread freshwater fish species, may comprise several species. Comparative ethological investigations can contribute to determining taxonomic relationships; this study compares the anti-predator behaviour of Galaxias in the presence of brown trout (Salmo trutta L.). The response of three distinct genetic types (A, B, and C) to trout differed: Type A Galaxias exhibited more inactive behaviour (increasing the frequency of the cryptic ''flat on the substrate'' posture: FS) during the day but not the night. Type B Galaxias showed no significant effect of trout on the proportion of its behaviour that was inactive, either during the day or night, but the relative frequency of cryptic FS postures FS postures at both times. Type C Galaxias exhibited more active behaviour both during the day and the night. Nevertheless, the relative frequency of cryptic FS postures was greater during the day (but not the night). The proportions of fish feeding were reduced for all three types, but least marked for Type C. Feeding rate was reduced during both day and night for Types A and B, but not for Type C. These findings support the hypothesis that the three types are different species, but further critical evaluation is required.