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Meridian research helps protect NZ native longfin eels

Press release
29 April, 2012

Meridian research helps protect NZ native longfin eels

Recent findings from research commissioned by Meridian Energy have revealed new information about the longfin eel’s habits and migratory behaviour, which will help to enhance efforts to protect the native species.

Meridian has been working with the National Institute of Water and Atmospheric Research (NIWA) on this six-year research project as part of its industry-leading annual trap and transfer programme in the Waiau catchment. This programme involves physically trapping female migrating longfin eels in Lake Manapouri and transferring them to below the Manapouri Lake Control structure – from here they have open access downstream enabling them to successfully migrate to sea for spawning. The programme also transfers young eels (elver) upstream into Lake Manapouri.

“Meridian is one of the only companies in New Zealand doing consistent large-scale eel protection work for both elver and adult migrants through its trap and transfer programme. Its commitment and support for the research programme demonstrates a genuine desire to ensure this precious species is protected for future generations,” said Dr Don Jellyman, Principal Scientist, NIWA.

Researching the movements of migrating eels around Lake Manapouri involved the use of acoustic receivers placed in key locations around the lake to track movement over six years of 220 tagged eels. Some receivers were able to record continuous tracking data, enabling a “3D” picture of daily eel behaviour to be built up.

This is the first time such comprehensive information has been recorded, and has led to new information about longfin eels that will assist in informing how to protect the species. Key findings are that:

• Eels do a lot more “vertical searching” at a potential outlet before selecting their final migration route out to sea than was previously understood to be the case.
• Where it was previously believed that eel migration occurred once annually, the research shows that migrations can occur over an extended period, with some eels migrating in spring, but most in late summer or early autumn.
• Not all migrations happen at night on a new moon; some migration occurs in daylight.
• Early in the migratory seasons eels can take up to a month to swim down the Waiau to the sea; later in the season they can make the 60 km trip in less than 24 hours.
• While it is known that eels typically migrate during higher flows, some eels were found to migrate during relatively low flows.
• Eels don’t eat when they’re migrating. From Southland the journey is around 4,000 km to the spawning grounds in the Pacific.

The research also confirmed that the vast majority of eels naturally make the right choices and migrate safely down the Waiau River. However, while eels can safely migrate on their own, Meridian increases their survival odds through the trap and transfer programme that assists around 2,000-3,000 eels each year, which is more than half the estimated migrating population.

Andrew Feierabend, Regulatory Strategy Manager at Meridian Energy says, “The longfin eel population is a key indicator of the quality of our waterways so it is very important to make sure they are protected. Meridian takes our responsibilities to the environment very seriously, and we’re always looking for ways to reduce our impact.”

While longfin eels are unique to New Zealand, the research findings have broader application to other types of eels around the world that are impacted by modified waterways. NIWA’s Dr Don Jellyman who led the research, which was peer-reviewed by a North American expert, presented the findings at the Seventh World Fisheries Congress in Edinburgh in 2012.

“Getting migratory eels downstream to breed is an international problem. There’s no silver bullet, but having a better understanding of eels’ migratory patterns is critical to devising solutions that will ensure the survival of the species,” said Dr Jellyman.

Found only in New Zealand, the longfin eel is one of the largest eels in the world. They have a long lifespan – with records of females that are well over 100 years old.


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