Fish Don’t Like to Leap or Crawl - an Update on Ensuring and Restoring Upstream Fish Passage

Degradation of habitat and construction of hydraulic structures such as dams or weirs that prevent fish from accessing suitable habitat have resulted in a decline in freshwater fish populations in New Zealand and other countries.

International expertise in the field of fish passage has improved considerably in the last two decades due to advances in sustainable catchment management, river restoration efforts and increased monitoring of existing solutions.

There are no common fish passage design standards or recommendations in New Zealand. However some regional guidelines exist for selected solutions, e.g. TP 131 and TR 2009/084 for the Auckland Region with a focus on fish-friendly culverts, and a fish screening guideline for Canterbury.

This paper imparts the latest knowledge of the construction and retrofitting of structures that enable or restore the upstream passage of fish, based on recent international expertise. Focussing on New Zealand freshwater fish species performance, the prerequisites that are decisive for the effectiveness and efficiency of fish passage are outlined. These are location (e.g. in-stream location and attraction flow) and passability (e.g. hydraulic conditions, orifice spacings and adaptation to up-/downstream water levels). A range of nature-like state-of-the-art solutions and fishway designs are also illustrated.