MEDIA RELEASE
 

Hornwort threatens Lake Okataina

For immediate release: 26 March 2009

Environment Bay of Plenty staff have been busy scouring the bed of Lake Okataina this week in an effort to locate the source of a hornwort incursion.

Hornwort (Ceratophyllum demersum) is one of the most invasive aquatic weeds as it is not as depth-limited as other invasive species. It can spread easily and rapidly displaces native vegetation in shallow and deep water.

The weed fragments were found by NIWA staff earlier in March and are likely to have arrived on a vessel used in nearby hornwort-infested lakes. Lake Okataina is one of only a handful of remaining Rotorua lakes with a low level of weed infestation.

Environment Bay of Plenty environmental scientist Matthew Bloxham said this recent find emphasised the need for boaties and anglers to check, clean and dry their equipment when moving between lakes to prevent incursions like this from happening.

“Okataina is a top spot for trout fishing and recreational boating. If hornwort were to establish throughout the lake it would make accessing areas of shoreline by boat and shore-based fishing difficult,” Mr Bloxham said.

Environment Bay of Plenty has gone to some lengths in recent times to keep hornwort and other invasive species from establishing in the lake. In 2007, one hornwort plant was found after a routine inspection by Environment Bay of Plenty’s aquatic weed surveillance team and the incursion was able to be neutralised.

“The weed surveillance team has already covered 10 kilometres of lakebed using SCUBA equipment. The signs are ominous as weed fragments have been found beach-cast over a wide area of shoreline,” Mr Bloxham commented.

The majority of high risk sites have been covered and the weed surveillance team are continuing to search the lake bed this week.
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