Distribution of native fish in the

4 www.biol.canterbury.ac.nz Executive Summary 1. The distribution of fish in the Ngakawau and Waimangaroa Rivers was investigated and compared with those in the Mokihinui River and several coastal streams to evaluate the influence of acid mine inputs from historic and current mining activities on freshwater fish occurrence. 2. Two approaches were used: a. To assess the expected occurrence of fish in the absence of acid mine influences, a model was developed to predict the distribution of migratory galaxiid (whitebait) species given the landform characteristics of the catchments. The model, based on recently published research, combined a stream network GIS with measurements of the ability of the fish to ascend slopes, move inland and their associations with land cover (all derived from distribution patterns in relatively pristine catchments). b. Secondly, to evaluate the actual distribution of fish, an extensive survey of 52 sites in the three catchments was conducted in November 2005. All sites were electrofished and many were spotlight-sampled at night. 3. The model predicted that inanga (Galaxias maculatus) and giant kokopu (G. argenteus) would be limited to coastal streams and the lowest reaches of the main rivers. Banded kokopu (G