INVERTEBRATE FAUNA OF 3 STREAMS IN RELATION TO LAND-USE IN SOUTHLAND,NEW-ZEALAND

A survey of benthic invertebrates and associated environmental factors was carried out in three Southland streams in relation to developed a nd undeveloped pasture over 15 months in 1985-1987. In all three strea ms the invertebrate community changed in the sections within developed pasture in such a way as to suggest pollution, although no point sour ces were present. Numbers of Deleatidium spp., Pycnocentrodes aureola, Olinga feredayi, Archichauliodes diversus, Aoteapsyche colonica, and Plecoptera tended to decrease in the developed pasture area, whereas n umbers of Potamopyrgus antipodarum, Physastra variabilis, Gyraulus cor inna and Oligochaeta tended to increase. Stepwise regression was carri ed out on six environmental variables vs seven of the more numerous ta xa. Significant regressions at P < 0.01 were obtained for 7 out of 21 instances, but little consistency was apparent across streams or taxa. The significant regressions that were obtained did not explain readil y the tendency towards a pollution-type community, and it is suggested that dips and drenches used on sheep in the developed pastures could be partly responsible for some of the changes.