​Abundance of Daphnia pulex observed in Lakes Te Anau and Manapōuri

Abundance of Daphnia pulex observed in Lakes Te Anau and Manapōuri

Environment Southland is investigating reported sightings of ‘white flakes’ in Lake Te Anau and Manapōuri.

Samples from Lakes Te Anau and Manapōuri were collected this week, and test results received this afternoon confirm that what is being observed is Daphnia pulex, an introduced, invasive, freshwater fauna species.

The Cawthron Institute advises that this species presents no risk to human health. However, Daphnia pulex can out-compete native Daphnia species, threatening the broader lake biodiversity by creating conditions for other invasive species to grow.

Environment Southland’s chief scientist Karen Wilson said Daphnia pulex is a known species that has previously been observed in many freshwater systems throughout New Zealand over several decades. However, this is the first time we have seen such a high abundance of this species in both Lakes Te Anau and Manapōuri.

“Our scientists are working closely with experts at the Cawthron Institute to understand the ecological impacts and implications.”

Typically, Daphnia pulex is barely visible with the naked eye, around 1-5mm. However, the size currently observed is large and can be seen as free-floating white flakes a few centimetres below the water’s surface.

“We expect the high abundance of Daphnia pulex to decline over the next few weeks. We will continue to monitor Lakes Te Anau and Manapōuri and investigate Lake Hauroko, Lake Monowai and Lake Mavora to determine if these lakes are also affected.”

All fishing, boating and recreation equipment should be checked, cleaned thoroughly and dried before using it in other waterways to avoid spreading the species further.

To learn more about preventing the spread of freshwater pests, visit https://www.thisisus.nz/check-clean-dry

ENDS