Passage of inanga (Galaxias maculatus) over artificial ramps as a means of restoring upstream access to stream habitat

Abstract

The effects of substrate type, flow rate, and slope on fish passage over artificial ramps was evaluated for inanga (Galaxias maculatus); a small diadromous fish native to New Zealand, Australia, Tasmania, Lord Howe Island, Chatham Island, Chile, Argentina, and the Falkland Islands. Five substrate types (smooth, corrugated, herring-bone baffle, and two plastic moulded cores of ground drainage products Polyfo® and Stripdrain®) were tested on slopes of 3 - 5 % and flows of 4 - 6 ls-1. Slope, fish size, and substrate type each had a significant influence on the mean distances swum. Stripdrain® was the most effective substrate type, enabling the greatest distances to be achieved and a maximum vertical elevation of 0.39 m to be attained. The results of this study have further highlighted the potential for ramps to provide fish passage past small in-stream barriers, as well as the need to refine ramp slopes and lengths in order to meet the specific barrier remediation needs.