Sockeye salmon are spawning in streams and rivers throughout the Waitaki catchment, from Lake Ohau to the lower Waitaki River, providing another attraction for anglers.
About eight years ago, the sports fish suddenly reappeared in Lake Benmore's Haldon Arm and about 700 were counted in the Ohau River.
They had previously been thought to have disappeared from the 1980s, when the upper Waitaki power scheme was built.
Initially, the population was only in Lake Benmore and used the Ohau River for spawning, but Central South Island Fish and Game Council officer Graeme Hughes said they had now been seen elsewhere in the catchment, including the lower Ohau River, Twizel River, Tekapo River, Ahuriri River, Mint Creek, Otematata River, Deep Stream, Awakino River, Hakataramea River and lower Waitaki River.
Mr Hughes said the sockeye had spread from Lakes Benmore and Ohau downstream, from water being spilled from the dams during floods, particularly in the past three or four years, and at times when they gathered at the top of the dams.
Lakes Aviemore and Waitaki now had populations.
Sockeye salmon arrivals in the Waitaki, Hakataramea and Awakino Rivers were recent after spilling over the Waitaki dam.
Last year, they appeared in the Ahuriri River for the first time.
Sockeye salmon were first introduced in 1901 in to Lake Ohau, but disappeared after dam construction.
They reappeared dramatically in Lake Benmore in 2006, their return a mystery.
They also returned to Lake Ohau.
Since then both the size and population of the salmon have grown.
The salmon are growing to about 1.5kg, providing another sports fish for anglers, but are difficult to catch.
Plankton feeders, they do not compete with brown or rainbow trout for food.
However, their fry are valuable food for trout, boosting numbers and weights.
