Rotorua's lakes are being put at risk by users who fail to complete basic checks to prevent the spread of pest-fish and weeds.
Swimming, fishing, boating and biodiversity is being jeopardised by lake users failing to complete checks before entering the water, according to Department of Conservation (DOC) and Bay of Plenty Regional Council officials.
The organisations will have an ongoing presence at boat ramps this summer as part of a campaign to stop the spread of aquatic pests such as koi carp, didymo and catfish.
Despite this presence, there have been repeated cases of lake users introducing pest weeds to lakes where they do not already exist.
"Unfortunately, we've noted lake users backing trailers into the Blue Lake (Tikitapu) with weed fragments attached. If users are not vigilant about cleaning their boats and trailers before launch it is likely that new aquatic pests will find a home in our lakes. This is really disappointing and the consequences could be long-term," said DOC's summer advocacy ranger Melissa van dan Heuvel.
"Tikitapu and Lake Rotoma are two of our more pristine lakes and popular for recreational use.
"The establishment of new aquatic pests would be devastating for the environment and significantly impact lake users."
Hornwort and other freshwater weeds spread rapidly, creating a weed mat smothering native fish and posing a risk to boat users and swimmers.
Lakes Rotoiti, Tarawera, and Rotorua have hornwort, elodea, lagarosiphon and egeria present.
Other lakes may not have established populations of these weeds, but are at risk when lake users transport equipment which has not been appropriately cleaned. Many aquatic weeds can establish from a single fragment.
Many pests are not currently confirmed in Rotorua's lakes.
"Catfish and koi carp and red-slider turtles are species that are common in the Waikato lakes and waterways. We definitely don't want them establishing here but that requires lake users being responsible," she said.
"All it takes is three simple steps - check, clean, and dry."
Free packs containing cleaning detergent and information on aquatic pests are available from the Rotorua DOC office, 99 Sala St.