Native fish and minimum flows in the Kakanui River

The purpose of this study was to determine the distribution of native fish in the Kakanui River, their importance, and to assess low flows for maintenance of native fish habitat. The mainstem of the river was electrofished at 13 locations from near the estuary to the headwaters 54 km upstream. Eleven native fish species were found. Eight of these were reasonably abundant and their requirements have been considered in this report. Habitat suitability curves were developed for native fish species from data collected in 32 North and South Island rivers. The suitability curves were then combined with instream habitat survey data from 5 reaches to predict how the area of habitat suitable for each native fish species varied for flows of 0.1-1. 5 acceptable flow for maintenance of habitat. The selection criterion was either the optimum or the point of inflection, that is, the point on the curve where the quality of habitat begins to decline more rapidly with flow. The habitat/flow relationships reflected the habitat preferences of the fish species. Higher flows provided more habitat for fast water species, whereas low flows provided more habitat for edge-dwelling species. Most relationships showed poorly defined points of inflection, and few showed clearly defined optima. Available habitat for the fast-water dwelling bluegill bully and torrentfish varied linearly with flow from 0.1 to 1.5 little variation with flow. Habitat/flow relationships for the edge-dwelling species (upland bully, common river galaxias, and redfin bully) showed that flow reductions would usually have little effect on their habitat. Common bully habitat was optimal at a flow of 0.5 inflection at 0.3 eels, torrentfish and bluegill bullies, but have little effect on the amount of habitat available for the other species. A minimum flow of 0.3 maintain acceptable habitat for native fish. The relationships between habitat and flow were used to select a minimum An increase in the minimum flow will improve habitat for common bullies, with a point of Longfin and shortfin eel habitat generally showed in the lower reaches of the Kakanui River would