PREDATOR RECOGNITION AND ANTIPREDATOR RESPONSES IN THE RAINBOWFISH MELANOTAENIA-EACHAMENSIS

Predator evasion behaviour patterns of three populations of rainbowfis h (Melanotaenia eachamensis) were compared. The populations differed i n the level of complexity of their natural habitats and the type and e xtent of predation. The predator recognition abilities of fish were as sessed by exposing them to models differing in their degree of predato r realism. The availability of vegetated cover and the location of the models with respect to cover were manipulated. Fish from Lake Tinaroo , a relatively open habitat containing numerous predators, showed stro ng changes in elective group size (EGS) in response to the different m odels but did not rely on cover as a place of refuge. In contrast, Dir ran Creek fish originate from a small, fast-flowing, structurally comp lex stream lacking predatory fish species, and they showed little abil ity to distinguish between the different models and responded to threa t by spending longer in vegetated areas. Members of the Lake Eacham ca ptive stock increased their EGS in response to models representing low threat and with more threatening models increased the amount of time spent in vegetated regions of the arena. The contrasting reactions to predatory threat displayed by these populations highlights the need to use a number of different response indices when comparing the anti-pr edator responses of different fish populations. These data suggest tha t the level of habitat complexity as well as prior predator experience influence anti-predator responses of different fish populations.