Lake Rotoiti is in the South Island of New Zealand. It is a substantial mountain lake surrounded by beech forest and is 82 metres deep. We stayed at Saint Arnaud, a small community at the northern end of the lake.
The first European to see the lake was John Sylvanus Cotterell on 18 January 1843. Other Europeans reached the lake in November 1843, and named it Lake Arthur, but the Maori name remained.
We took a boat and short hike to Whiskey Falls which are named after an illicit still found there in the 1880’s and they are an impressive 40 metres high.
The lake is famous for New Zealand’s very own freshwater monster, the longfin eel. Scientists believe that the New Zealand longfins are quite possibly the largest eels in the world. Males reach about 75 cm in length before they head off to spawn. In contrast, the females tend to live and grow much longer; the bigger a female grows, the more eggs she will produce. No one knows exactly how old they get, but by counting the tree-like rings on the otolith—small, calcified bones in the ear—scientists have found that the eels of Lake Rotoiti live to well over 100 years.
For catching their prey, they rely on smell, with sizable “horns” on their upper lip which support a large nasal cavity that extends to the roof of the mouth. Their sense of smell is much greater than even that of the great white shark and any small quantity of blood in the water will soon lead to a large congregation. There are many stories and one or two genuine anecdotes of humans being attacked by groups of eels.
The longfin’s feeding mechanisms resemble that of another top predator, the crocodile. Like their reptilian counterparts, eels are classic ambush predators, concealing themselves and lunging at hapless victims as they pass.
The adults eventually leave their home and travel thousands of miles into the Pacific Ocean to spawn. The baby longfin’s journey back to New Zealand waters is possibly more incredible. Eels start out life as tiny, toothed larvae, which form part of the plankton. After seven to nine months in the open ocean, they arrive on New Zealand’s coast between July and December. Under the cover of night, they gather and ride the spring tides in to shore. Once in fresh water, they develop into darkly-pigmented juvenile eels, or elvers, which congregate in summer and begin a mass migration far upstream. It is believed it takes from 2 to 5 years of traveling before they reach their destination for the next several decades.