MGI Aquatic Ecology Survey

The MGI Aquatic Ecology Surveys – Stage 1 were undertaken to address known gaps in ecological information across the MGI scheme. The purpose of the work was to establish a robust ecological baseline, improve understanding of aquatic values, and identify the distribution of high‑value species within the scheme area

The survey assessed 42 sites across the Scheme command area. These sites were selected to complement existing Environment Canterbury monitoring locations, fill spatial data gaps, and assess the ecological effects of bywash and surplus flows. Methods included rapid habitat assessments, macroinvertebrate community sampling, and fish surveys, using recognised national metrics aligned with the NPS‑FM

Results showed that many waterways within the MGI network have good to excellent instream habitat quality,

The surveys identified high ecological values, including diverse fish communities and the presence of Threatened and At Risk species. These included Canterbury mudfish (with two newly identified populations) and several At Risk native fish such as longfin eel, inanga, kōaro (gallaxid), giant bully, and torrentfish.

The surveys also confirmed the presence of kākahi (freshwater mussels), an At Risk species, that is a valued mahinga kai species and of conservation significance. Kakahi were found at Bells Pond, which was identified as a site of particularly high ecological value, Top Pond and Waikakahi Stream. Undertaking snorkel surveys, there were 1,315 kakahi found in Bells Pond; 3,690 found in Top Pond; and a maximum number of 3,725 along 11 sites in Waikakahi Stream.