App to help fish breed

Ōtānerito Bay was part of a trial to identify streams with potential barriers to migrating fish.

An app is being used to identify in-stream barriers which can stop fish completing their life cycles.

Environment Canterbury, the city council and Department of Conservation have been trialling the app created by the National Institute of Water and Atmospheric Research to identify sites with obstacles to fish migration.

For two weeks in November and December last year, Canterbury University student Megan Brown walked over parts of Banks Peninsula considered data-deficient – meaning there isn’t a lot of information about streams in the areas.

They included Port Levy, Okains Bay, Ōtānerito Bay, Tumbledown Bay, Flea Bay, The Kaik and Lake Forsyth.

Ms Brown recorded 59 potential barriers (mainly culverts) for fish across these areas and identified two sites as being in need of remediation to remove barriers – Narbey Stream Tributary in Otanerito Bay and an unnamed stream on Port Levy/Pigeon Bay Rd in the Kokourarata Stream catchment.

A barrier is considered to be any structure such as a weir or culvert that fish cannot swim, climb, jump or wriggle past.

This is important because many New Zealand fish – including whitebait and eels – are migratory and barriers prevent them from completing their life cycle.

After visiting the areas and completing a visual assessment of potential barriers to fish passage, Ms Brown entered the data into the NIWA app.

Information such as drop height, overhang length, water velocity and culvert length were recorded to inform a determination of the fish species that would be preventing from passing by the structure.

The information was used to identify the two worst-affected sites.

Biodiversity funding from the Banks Peninsula Water Zone Committee may be used to complete remediation work on the sites.