ONTOGENIC HABITAT SHIFTS BY GALAXIAS-GRACILIS (GALAXIIDAE) BETWEEN THE LITTORAL AND LIMNETIC ZONES OF LAKE-KANONO, NEW-ZEALAND

Diel and spatial differences in distribution were determined for the l arvae, juveniles, and adults of Galaxias gracilis (Galaxiidae) in a Ne w Zealand dune lake during summer months. Larvae (mostly 10-25 mm TL) and juveniles (25-40 mm TL) inhabited shallow (0-3 m) waters of the li mnetic zone and fed predominantly on two limnetic zooplankton species; Bosmina meridionalis and a calanoid copepod. At about 40 mm TL, fish moved from the limnetic to the littoral zone and expanded dietary brea dth from two to over seven main prey species, including five species o f littoral invertebrates. After reaching a size of about 60 mm TL, mos t fish moved back offshore to the deeper waters (5-15 m) of the limnet ic zone during the day, moving back to the littoral zone at night to f eed on invertebrates. The selection of different intra-lacustrine habi tats by the various size groups of G. gracilis, and the movements betw een them, are interpreted as adaptive responses to the interaction bet ween ontogenetic changes in feeding requirements and predation risk.