Removal of aquatic vegetation is underway in parts of the Taylor and Lower Opaōa rivers, with Council’s weedcutting boat busy working until the end of January.
Under rules in the Marlborough Environment Plan, certain river works are not allowed in the tidal parts of the Taylor and Opaōa rivers from 1 February to 30 April to avoid the fish spawning season, meaning removal of aquatic vegetation cannot be carried out up to the Alfred Street bridge during that three month period.
“The primary fish species we are protecting are inanga; juvenile inanga are the main species that make up the whitebait catch,” Andy White, Council Rivers and Drainage Engineering Manager said.
“Dramatic changes in water level that occur when the aquatic vegetation is cut can impact the success of inanga’s annual breeding season. A host of other bugs and birds also benefit from a river ecosystem with natural plant growth.”
“A number of environmental factors have combined in recent years which mean that we may again see flooded boardwalks in the autumn, depending on rainfall.”
“Last year we had a fairly wet summer on top of two major storms in 2021 and 2022, which means there has been much more siltation - or aggradation - of the river bed,” he said.
“This is part of the natural behaviour of all rivers when rainfall is heavy or prolonged.”
“Aquatic vegetation is actually a relatively small part of the problem - the main issue is sedimentation - the river bed has gradually risen over recent years.”
A longer term solution to aggradation is currently in development with additional funding sought as part of this year’s Long Term Plan.
He said if the weather remained dry it’s likely that the river’s water level would stay fairly low.
