Wellington Fish & Game have renewed an attack on the mechanical control methods used by Greater Wellington Regional Council (GWRC) in Wairarapa rivers.
Manager Phil Teal said Fish & Game was increasingly receiving complaints about GWRC's method of cross-blading, not just from fishermen, but also from the wider community.
Mr Teal said the in-stream river works with bulldozers had resulted in the Ruamahanga River becoming a "barren channel", with repercussions on fish stocks such as valued sportfish like trout and native species.
Cross-blading with bulldozers lowers the riverbed by creating a steeper gradient, reducing the risk of flooding.
"We'd have an expectation that sections that have been worked would recover within a reasonable timeframe," Mr Teal said.
"However, there are examples of pools that fish lived in -- and people swam in -- along with the insect life that fish fed on, not returning, even a year or longer after the bulldozers have been in the rivers."
He said GWRC's method of mechanically breaking up the riverbed significantly reduces the surface flow of the rivers, "causing higher water temperatures and exacerbating algae and weed growth".
"This is poor practice in a drought-prone region," he said.
According to NZ Fishing, the practice of cross-blading with bulldozers is illegal in many European river systems, where authorities now opt to allow naturally occurring swamps and marshlands to re-establish.
Mr Teal said Fish & Game accepted that towns in Wairarapa needed to be protected from floods but the scale of the works undertaken "appears excessive in some cases and goes well beyond that brief".
Former Green Party candidate for Wairarapa and Dam Free Mangatarere chairman Michael Woodcock said the aesthetic result of cross-blading was "not the sort of thing we put on our tourism brochures".
"These actions ignore that rivers are living entities with life in them," he said.
"This treatment in the name of best practice sanctioned by regional and local councils stuffs up beautiful places and turns them into drainage ditches."
GWRC were approached for comment and will be preparing a response at a later date.