Barred grunters shift objects to access benthic invertebrates in a crater lake

Abstract

Benthic structure mediates food web processes shaping benthic communities. By way of direct manipulation of benthos, the barred grunter Amniataba percoides is the third species of fish from the family Terapontidae (a mostly tropical central Pacific family of fishes) to be found manoeuvring benthic objects in search of prey. A popular lakeside swimming beach in the Australian Wet Tropics provided the arena for these observations, and the fish both exhibited pebble-rolling behavior in making use of the modified landscape (i.e. at a pebble beach) and had become accustomed to human activity whereby fish fed by congregating around disturbance caused by the legs and feet of swimmers. Amniataba percoides of juvenile and adult size manoeuvred gravel, pebble, cobble and allochthonous objects including bark, sticks, and leaves and fed from the surfaces of these objects and from the soft sediment exposed from beneath the objects. This fish species is human-oriented and warrants further investigation in terms of individual specialisation in both fish species rich and species poor assemblages and in the presence and absence of human aquatic activity.