Following three days of searching by a team of four divers, the Department of Conservation (DOC) is pleased to announce that Southland lakes remain free of the ‘space invader’ aquatic weed known as lagarosiphon.
Boat ramps at Lakes Te Anau, Manapouri, Monowai, Hauroko and Mavora, as well as other high risk locations, were part of the annual surveillance programme which is co-funded by DOC, Environment Southland and Meridian Energy.
Lagarosiphon, also known as oxygen weed, is a fast-growing weed that chokes lakes and waterways. It can form dense patches that prevent boating, fishing and swimming as well as crowding out native aquatic plants. It has become a major problem in some Central Otago lakes but so far has not invaded Southland lakes.
DOC Te Anau Freshwater Ranger Sanjay Thakur said lagarosiphon is potentially the worst aquatic pest plant threat in the South Island. “Once established, it is very hard to get rid of”.
Lagarosiphon is most commonly spread by contaminated boats and trailers, as well as on fishing, diving, swimming and ski gear. People emptying fish tanks into rivers and lakes can also spread aquatic pests.
While it is great news that Southland’s pristine lakes all appear to still be free of lagarosiphon, Mr Thakur is urging boaties and other users of Southland waterways to remain vigilant. “Before you leave the boat ramp, clean any weed off your boat’s hull, motor, intakes and trailer. Make sure all your fishing gear, kayaks and swimming gear are also free of weed before you leave the area”.