Northland lakes, ponds and dams under scrutiny for pest species

Biodiversity advisor Brooke Hartigan at Whangārei's Dragonfly Springs. Hartigan is holding fibreglass mounts of two unwanted pest fish, a tench, left, and a perch.

Moves are under way to further pull the plug on invasive weeds and exotic fish in Northland's lakes, ponds and dams.

Biodiversity experts are pleased with the public response to a survey that will help steer future management of freshwater pests.

New biological data was needed about Northland's 372 lakes, ponds or dams, all bigger than 0.5ha, which were not among the 100 already monitored by Northland Regional Council (NRC) and the National Institute of Water and Atmospheric Research (Niwa).

Among key findings were three new reports of invasive pest fish species, now being investigated with a view to further action, including removal.

Eight dune lakes classed as ecologically high or outstanding, or near a lake with those rankings, have been prioritised to have exotic fish removed.

A third of the landowners who were written to asking for their co-operation replied favourably to the NRC's request for surveying help. Council chairman Bill Shepherd said he was delighted with that level of public feedback.

NRC lakes biodiversity advisor Brooke Hartigan said the survey identified some key conclusions and resulted in more than a dozen recommendations.

They included fish removal, training interested landowners and community members about invasive fish, a public awareness campaign, new signs and educational tools.

"Creation of a Freshwater Pests Pathways Management Plan or site-based plans for invasive fish and water-weeds has also been recommended," Hartigan said.

Egeria (oxygen weed) was the most frequently found weed, while gambusia and rudd were the most common fish.