RELATIVE EFFECTS OF IN-STREAM HABITAT AND LAND-USE ON FISH DISTRIBUTION AND ABUNDANCE IN TRIBUTARIES OF THE GREY RIVER, NEW-ZEALAND

The distribution and abundance of fish was investigated over 2 years a t 78 sites in Redjacks Creek and adjacent tributaries draining native, exotic, and mixed forest catchments within the Grey River system, Sou th Island, New Zealand. The abundance of diadromous fish decreased wit h altitude and distance from the sea, whereas the abundance of non-dia dromous fish species, especially dwarf galaxias (Galaxias divergens), increased with altitude and distance from the sea. Species abundance v aried with average stream depth and velocity, generally in accordance with micro-habitat preferences. The relative influences of diadromy, l and use, and physical habitat on fish distribution and abundance were difficult to separate. Differences in fish abundance in the three land -use categories were often attributable to differences in physical hab itat. Nevertheless, there were indications that land use and its effec t on the stream environment was influencing the distribution of some f ish species. Ammocoetes (Geotria australis) were least abundant in nat ive forest catchments, whereas dwarf galaxias and bluegilled bullies ( Gobiomorphus hubbsi) were abundant in those catchments. Banded kokopu (Galaxias fasciatus) were associated with in-stream cover and only fou nd in the smallest streams sampled. The abundance of torrentfish (Chei marrichthys fosteri) and bluegilled bullies declined over the study pe riod, and three fish species were found in catchments adjacent to Redj acks Creek, but not in Redjacks Creek or its tributaries. Suspended se diment produced by mining and logging activities may have caused low f ish diversity and changes in fish abundance in Redjacks Creek.