May 23, 2014

A celebration of fish migration

Saturday 24 May is World Fish Migration Day, a subject close to the hearts of Horizons Regional Council’s freshwater management team.

The Horizons Region is home to 17 species of native freshwater fish and Council staff have been working in partnership with landowners, Wanganui District Council, and the New Zealand Transport Agency (NZTA) to help these fish move freely through waterways.

“Many people don’t realise the diversity of fish life that inhabits our rivers and streams, particularly as many of them are nocturnal and so not easily seen” says Clare Ridler, Freshwater Coordinator for Horizons.

“Some of our native fish are really good climbers, others less so. We’ve been working with Wanganui District Council and our engineering team to determine the best solutions for rivers and streams where fish passage is compromised by culverts or flood protection works.”

A key focus of recent work has been in the Awarua Catchment – the stream that flows down by the State Highway at Marybank then goes under the road to the Airport before flowing into the Whanganui River.

The landowners downstream of the State Highway have been working with Horizons to fence off and replant their streamsides in native trees and shrubs. Wanganui District Council has also installed two fish passes with funding from the Whanganui River Enhancement Trust, with the goal that native fish should be able to move from the river up into a range of habitats.

Kritzo Venter, Wanganui District Council’s Senior Stormwater Engineer, says “the culverts on Wikitoria and Nepia Roads were perched which means they create a waterfall which many of our native fish are unable to climb. By putting in a rock ‘ramp’ and bracing it with concrete it allows a gentler slope with many resting areas behind rocks.

“This will help the fish with their migration up into the culvert and upstream.”

The project’s next step is to finalise a solution with NZTA to allow passage of fish along side the state highway using plantings to provide shade and protection.

Other measures put in place by Horizons to help fish swim freely in rivers and streams range from baffles created using rocks and mussel rope for fish to climb up, to weighted flood gates installed in areas such as Tangimoana where traditional flood gates are restricting fish movement.

Ms Ridler says the chosen solution is dependent on fish species, in-stream environment and the type of obstruction.

Native fish species found in the Horizons Region include: dwarf galaxids, brown mudfish, redfin bully, bluegill bully, lamprey, common bully, giant bully, torrentfish, smelt, longfin eel, shortfin eel, inanga, koaro, giant kokopu, banded kokopu and short jaw kokopu.

The latter five species make up the whitebait catch and over 90 percent of those caught are inanga.

Adult inanga lay their eggs in the dense long grass along stream banks during high tides in February and March. These eggs hatch during the next high tides and larvae are carried out to sea. Work has been underway locally by Horizons to search for and map these spawning zones, in order to protect the key areas for egg laying, which should help lead to more whitebait migrating back up.

“One key message is that if you find whitebait crawling up the side of the bucket holding your whitebait catch, please consider releasing these as they are likely to be koaro; one of the rarest of our whitebait species,” Ms Ridler says.

Horizons’ State of Environment report released in 2013 shows maps of sites where native fish have been found. It states that while additional populations of rare and threatened species were discovered during a survey in 2011, predictive modelling suggests there should be significantly more native fish in significantly more sites.

“We’re hoping to increase the awareness around native fish species and their migratory patterns, and World Fish Migration Day on Saturday is a great way to do this” Ms Ridler says.

Horizons is running a colouring competition to aid this awareness. Copies of the colouring competition are available from the Horizons website or by contacting Horizons’ freshwater team on toll free 0508 800 800.

The colouring competition has three age categories for entries: under 6, 6-9 and 9-12. Winners will receive native plants for their homes or schools and all entries must be in by 5pm Friday 30 May.

Horizons Regional Council, the Whanganui River Maori Trust Board,the Department of Conservation, commercial businesses and land owners are all part of Healthy Streams Whanganui, an initiative led by Wanganui District Council to to keep waterways clean. If you want to know more about the Healthy Streams project, please email kritzo.venter@wanganui.govt.nz.

ENDS

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