Hornwort at Lake Rotoiti
Heralding the horrors of hornwort
The lovely Lake Rotoiti at risk from aquatic weeds
Nelson Lakes National Park is currently free from aquatic weeds such as hornwort and lagarosiphon. DOC staff are desperate to keep it this way and take every opportunity to communicate the risk and educate people about how these weeds spread. The annual boating regatta at Lake Rotoiti 2003 was the perfect opportunity. Attendees learned about the importance of cleaning boating gear and why not to empty fish tanks into waterways.
Hornwort
Lake Rotoiti Regatta 2003
The sun was shining, the birds were singing, the bugs biting, and the lake was alive with the splashing of …oars and the hum of engines? That's right; it was time for the annual boating regatta at Lake Rotoiti (Nelson Lakes National Park). Every year over two weekends in February, power and classical-boating enthusiasts make an annual pilgrimage to the lake to admire boats and to compete in races.
But behind this day of fun, there is a very serious risk - the spread of aquatic weeds. Submerged weeds such as hornwort, lagarosiphon and egeria have an uncanny ability to suddenly appear in a lake or waterway. How does this happen? Rest assured, these aquatic weeds can neither walk nor fly. What they can do, with alarming alacrity, is break into small fragments that get stuck on boats, boating gear, and fishing nets and then get carried around the country.
Aquatic weeds grow in dense blankets, altering habitats for native flora and fauna, smothering native aquatic plants, clogging intakes on jet boats, fouling propellers and preventing fishing and swimming. Once aquatic weed has established in a water body, it is notoriously hard to get rid of, so prevention is by far the best option. By simply cleaning boats and boating gear we can help stop weeds spreading.
DOC staff were present at the regatta to warn boaties about the horrors of aquatic weeds, and the message was simple: stop the spread by cleaning your boats and gear. So with posters, flyers, live samples, a talk from weed ecologist Melanie Newfield (Nelson/Marlborough Conservancy), and the piéce de résistance - a DOC boat covered with pieces of weed (plastic of course!), hundreds of people took the message away. The competition to count the pieces of weed hidden on the boat was popular with the kids, and gave a clear message to all adults.
Hornwort
The aquatic weed display included information on hornwort, lagarosiphon and Egeria densa. None of these weeds are present in Lake Rotoiti, and in fact hornwort was only just discovered in the South Island last year (a small number of infestations around the Nelson region). Hornwort is certainly the worst of a bad bunch, and will be horribly familiar to those working the North Island hydropower stations, where it has clogged turbines and cost millions of dollars. However, lagarosiphon is not far behind in the notoriety stakes, and in the South Island, Meridian Energy are investing into a programme along with DOC, Environment Southland, Environment Canterbury, Otago Regional Council, Ngai Tahu and Land Information NZ. This campaign encourages boaties to take action and clean their boats and boating gear to prevent the spread of lagarosiphon.
As well as spreading around by sneaking onto boats and boating equipment, aquatic weeds like hornwort and lagarosiphon often get around by people emptying fish tanks and ponds into drains. Both lagarosiphon and hornwort were once used in aquaria, but both are now banned from sale.
By taking some simple steps we can all prevent a massive problem. So help stop the spread and encourage others to do the same:
- Clean your boat, boat trailer and boating gear
- Remove any fragments of weed from nets and fishing gear before you leave an area
- Don't empty your fish tank into or near a waterway
- Don't drain any ponds into water bodies unless they are free of weeds.
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