Effects of the presence of subadult longfinned eels (Anguilla dieffenbachii) on cover preferences of juvenile eels (Anguilla spp.) in replicate channels

The effects of the presence of subadult (420-875 mm total length (TL)) long finned eels (Anguilla dieffenbachii Gray) on day-time cover preferences of three juvenile size groups (small <100;, medium = 100-199; large = 200-299 mm TL) of shortfinned eels (A. australis Richardson) and longfinned eels we re tested in replicate channels provided with natural (macrophytes, cobbles , woody debris) and artificial (shade, plastic pipes) cover. Macrophytes, c obbles, and woody debris were the most frequently occupied cover by both sp ecies of juvenile eel, whereas overhead shade and plastic pipes were rarely used. In most instances, the subadult longfinned eels occupied the macroph ytes, the cover type preferred by juvenile eels when tested in the absence of subadult eels. The small juvenile eels used the three natural cover type s similarly between species, whereas the cover preferences of medium and la rge juvenile eels differed between species-whether tested in species unmixe d or mixed situations, shortfinned eels preferred macrophytes and longfinne d eels preferred cobbles. It is concluded that as juvenile eels increase in size in the wild, their cover preferences will be more restricted because of greater interaction with that of predatory subadult eels in the populati on.