Evaluation of cone fishways to facilitate passage of small-bodied fish

Fishways are being provided more regularly than ever before and new designs are needed to provide passage for whole fish communities. Despite recent progress, fishways have frequently performed poorly, especially for small-bodied fish (i.e. 10–100 mm long), which can form large aggregations below stream barriers. This was the genesis for the development of the cone fishway design, a new style of technical fishway which consists of a series of pre-fabricated cone-shaped concrete baffles installed laterally within a concrete channel. The cone design arose from the need to install rock ramp fishways at remote sites where rock was unavailable and where maintenance would be infrequent. The objective of the present study was to evaluate the suitability of the new cone fishway design to provide passage for small-bodied diadromous species (i.e. <100 mm long). Cone fishways were evaluated at three low head (e.g. <3 m high) case-study sites in tropical and temperate Australia and in total, 45 species and 28,556 fish were collected. There was passage of a broad range of the target size-classes of small-bodied fish and individuals as small as nine mm could ascend. However, further work is needed to quantify the proportion of the small-bodied fish population in the river downstream which find and pass through the cone fishways. The most suitable experimental application of the cone fishway is at sites where there is: (i) a narrow (e.g. <0.4 m) headwater range, and (ii) where passage of small-bodied fish is a major ecological priority. Cone fishways provide a useful and novel option to improve passage of small-bodied fish, at appropriate sites, and contribute to a contemporary vision of restoration of whole fish communities.