Pilot Study of Macroinvertebrate Communities in Central and North-West Rivers, NSW

"August 1992".

Project Number: Pilot Study of Macroinvertebrate Communities in Central and North-West Rivers, NSW - M/04/188.

MDFRC item.

44 pages.

At five stream sites in the Gwydir Basin and one on Gil Gil Creek, immediately to the north, two series of artificial substrate samples and one series of hand-net samples were used to assess the macroinvertebrate communities. Based on the composition of these communities similarity analysis resulted in the sites falling into three groups. Group I consisted of a single upstream site included as a "control". Group II was composed of two sites (Gwydir and Carole Creek) in the vicinity of Moree. Group III contained three sites (downstream and to the west). Macroinvertebrate communities at sites in Group II differed considerably from the other sites in containing larger numbers of annelids and molluscs (amongst others) and lower representations of ephemerop.terans and trichopterans. This difference may represent a shift from allocthanous (from outside the stream) food supplies to an increase in autocthanous production, and possibly an increased degree of breakdown of organic material. Initial observations indicate that chironomids may provide a means of long-term routine monitoring after initial surveys have characterised the total macroinvertebrate communities throughout annual cycles. The work reported here, although preliminary, indicates significant differences across the catchment and should act as a foundation upon which to establish a definitive survey.