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Cold Stream culvert .. Hurunui farmer Ben Ensor has been working with Environment Canterbury to protect waterways and native fish on his property. PHOTO: SHANE ORCHARD

By David Hill

A Hurunui farmer has been doing his bit to protect native fish on his property.

Ben Ensor, who has farmed Willowgrove for 15 years, has been working with Environment Canterbury (ECan) to identify ways to improve migratory fish access to a wetland habitat.

“The waterways are amazing with their water quality and clarity, so we want to do what we can to make them better,” he says.

“The stream has been our farm’s water source, with pipes and troughs added as we fenced areas off for protection.

“The next stage is looking at what we can do for everything that lives in the stream.”

Surveys conducted near the Cold Stream culvert revealed several migratory species including redfin bully, not previously seen in the area.

The findings will inform recommendations on how to alter, build upon, or shift the culvert to allow safe passage for the fish.

The project has been funded by the ECan regional fish habitat fund and all data will be added to the national freshwater fish database, which stores and displays more than 34,000 freshwater fish observations across New Zealand.

Mr Ensor said both longfin and shortfin tuna/eel were found in the creek, along with some other native species.

“We also see flounder in there on occasion.”

Stream survey .. A survey by Environment Canterbury has revealed several migratory species, including redfin bully, on Hurunui farmer Ben Ensor’s property. PHOTO: MICHAEL BENNETT

Culverts, dams and fords present a variety of challenges to migrating fish because different species have different abilities, with some swimming while others climb, ECan land management and biodiversity adviser Heath Melville says.

Any changes to fish passages need to be designed to suit the species that will use them.

Surveys help to understand the number, size and type of fish present in waterways, Mr Melville says.

“They also help us find out about freshwater habitat, how it connects to other waterways and what may be having detrimental impacts on water quality.

“They can also reveal the whereabouts of unknown populations of endangered non-migratory fish species such as kowaro/mudfish that might be upstream of the barriers that are protecting them from predatory trout.”

Before any plans for the culvert were made, investigations were needed to see if any non-migratory species were living upstream of the Cold Stream culvert.

“It is important that we avoid impacts on resident species if we open the passage, so we need to know what’s there before proceeding,” Mr Melville says.