Water update

Easier passage for native freshwater fish

Native freshwater fish are being offered an easier deal in their pursuit to get upstream.

Our stream improvements programme provides fish passes or passages across previously impenetrable man-made obstacles like pipes and culverts.

The outfall of these obstacles is often higher than the stream water level, forming a sizeable drop which the fish cannot swim up.

The fish passes programme is thought to be a first for councils throughout New Zealand, and was initiated as part of our stream restoration work – recognising the ecological importance of native fish species prevalent in North Shore City waterways.

Such species migrate up and down streams for food and spawning, and their survival depends on the success of annual upstream migration of juveniles.

The fish passes or ramps need to be strong enough to withstand winter rains and floods. We’re constructing ours from rocks covered with a wire frame, which initially allows water to flow through.

Before long, the voids fill up with leaves and other materials, enabling water to flow over the top and creating an easier passage for fish.

Above:Stormwater projects engineer Paul Teutenberg at the upper regions of the Eskdale stream in Birkdale, site of one of our new fish passes designed to help freshwater fish in their journey up stream.