Whitebait are running in the Clutha River, an unusual occurrence for Otago, which usually experiences a slow start to the whitebaiting season, the Department of Conservation says.
The whitebait season begins today around the country except for the South Island West Coast, where the season begins on September 1.
Doc freshwater ranger Pete Ravenscroft said there had been reports of shoals of whitebait 10m long running in the lower Clutha in the past month, attracting illegal whitebaiters, although none had been apprehended.
"It's unusual this early on. Fingers crossed, it means a good season."
Rivers were looking good, except for the Taieri, which was discoloured.
Whitebait generally did not like running up dirty rivers, he said.
Whitebait numbers had been declining during the past five years since the last good season, he said.
All but one species of whitebait was "at risk", so smarter management of their habitats was needed especially on larger waterways like the Taieri and Clutha rivers.
Doc freshwater fish specialist Jane Goodman said experts had been returning to streams and rivers with historical records of adult whitebait [galaxiids] and finding that they were no longer present.
"Experts are very concerned about this trend and are endeavouring to document this decline and the reasons for it."
Inanga were the most common species, but whitebaiters might also capture the young of giant kokopu and shortjaw kokopu, which are threatened, or the koaro and banded kokopu.
Water removal, pollution, wetland drainage, introduced pests and destruction of stream-side vegetation were some of the issues that threatened the long-term survival of whitebait species.
Doc reminded whitebaiters to be aware of the regulations and to be within 10m of their gear at all times and to check, clean and dry their gear when moving between or up waterways, to prevent the spread of didymo algae and other aquatic pests.
"Generally speaking, whitebaiters observe the regulations that help keep a healthy fishery, but we all have to be aware of contaminated whitebaiting gear affecting other streams."
