Colonization of Perspex Strips by Larvae of Austrosimulium-Bancrofti (Taylor) Near Willawarin, Nsw

Abstract

A total of 14 113 larvae of the taxon Austrosimulium bancrofti (Taylor) was collected from perspex strips placed in the MacLeay River. The method of multiple mixture modelling separated larvae into seven instars. Highest numbers of instar III and fewest of instar VII were collected. Significant effects influencing colonisation of the perspex strips were incorporated into a statistical model. This permitted generation of fitted estimates of the number of larvae colonising strips under defined conditions. Fitted captures indicated that higher numbers of larvae colonised strips with increasing water depths (7 less-than-or-equal-to X less-than-or-equal-to 46 cm) and when there was no vegetation beneath the strips. Strip texture, quadratic terms for distance from one river bank and their interaction significantly influenced numbers collected. Fitted estimates demonstrated fewest larvae colonised strips in midstream but this decline was most distinct for the smooth strips. Quadratic terms for water velocity and their interaction with strip thickness also influenced larval colonisation. Fitted estimates were highest when water velocity was in the range 1.05-1.25 m s-1 for each strip thickness.