Northland Lakes Ecological Status 2012

The Northland Regional Council engaged NIWA to update the Wells and Champion 2011 Northland Lakes Status report by providing the following assessments of lakes and water bodies:

Ecological assessment
Endangered species identification, wetland extent and species composition, submerged vegetation abundance and composition including LakeSPI assessment, water bird, fish and aquatic invertebrate presence and abundance, and processing findings to assign a Lake Biodiversity Assessment ranking.

Central Northland
Lake Kaiwai and Lake Omapere

Lake Humuhumu; Lake Kahuparere; Lake Karaka; Lake Mokeno; Lake Rotokawau; Lake Roto-otuauru / Swan; Lake Rotopouua; Lake Rototuna; Lake Whakaneke

Grass carp assessment - Lake Heather and Lake Roto-otuauru / Swan.

Weed surveillance - Lake Humuhumu, Lake Kai-iwi, Lake Ngatu, Lake Taharoa, Lake Waikere, and Lake Waiporohita.

Lake Kaiwai - ecological assessment was carried out for the first time.

Lake Omapere - margins have been found to support populations of two nationally critical plants.

Lake Humuhumu - remains ranked an “Outstanding” lake.

Lake Kahuparere - is ranked as a “High” value lake.

Lake Karaka - is a “High” ranked lake with an indigenous vegetation and fauna and much of the margin surrounded by wetland including nationally endangered plants, fish and birds.

Lake Mokeno - remains ranked as an “Outstanding” lake.

Lake Rotokawau - is a “High” ranked lake.

Lake Roto-otuauru / Swan - has a “Moderate” ranking.

Lake Rotopouua - is an “Outstanding” ranked lake.

Lake Rototuna - is a “High” ranked lake with retired margins.

Lake Whakaneke - is a “Moderate” ranked lake, near Lake Mokeno.

Weed surveillance
No new weed incursions were found in the six high-risk lakes monitored.

Grass carp results

Lake Heather - After 2 years of grass carp in the Lake Heather the egeria (Egeria densa) has nearly all gone and about 50% of the hornwort (Ceratophyllum demersum) has been removed.

Lake Roto-otuauru / Swan - Progress with hornwort and egeria eradication has been rapid with no traces of these weeds found (after 3 years of grass carp).