Native fish populations in the Manawatu River catchment will be increasing thanks to a man-made fish ladder created from concrete and rocks installed at Tokomaru Stream by Horizons Regional Council.

The pass was created 19 months ago for migratory native fish to find their way upstream to freshwater and continue their life cycle.

Last month Horizons Regional Council freshwater and partnership manager Logan Brown and freshwater management officer Anna Regtien dyed 200 inanga (whitebait) red and released them alongside 200 non-dyed inanga below the pass to test if the ladder worked by isolating the section of stream the fish pass.

They spotted 143 inanga that made it to the top.

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Regtien said it was a great success as many were small size inanga, the weaker swimmers of the whitebait species.

"We could also see a lot still in the water at the top of the pass that hadn't swum into the net yet," she said.

The fish pass is designed for all migratory native fish species found in the catchment.

"Now we have found that our fish ladder is successful we will do the same thing in other places, so if members of the public know of any man-made barriers or landowners who would like to fix known barriers then please get in touch with the freshwater team at Horizons Regional Council.

"We can open up more habitat, which ultimately means people have more fish to catch," Regtien said.

The plan is to install four fish passes this summer alongside fencing and planting under the Manawatu River Leaders' Accord.

Brown said four out of five of the whitebait species are in decline.

"The work we do in fixing fish barriers means native fish can access more habitat, and hopefully by increasing the habitat will increase the populations," he said.

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The Manawatu River Leaders' Accord was signed by iwi, local and central government, and farming and environmental groups in 2010, pledging to take responsibility for the poor health of the river and improve it's mauri (lifeforce).

In 2012, the accord received $5.2 million from the Government, plus approximately $46m from Accord partners, one of which is Horowhenua District Council.

The fund has contributed to more than 66,420 native plantings alongside waterways; more than 208,487 metres of stream fencing; 98 Environmental Farm Plans completed to help farmers reduce the environmental footprint of farming; 12 fish passage improvements; six wastewater treatment plant upgrades; and 19 community-led projects completed or under way.