Temuka anglers say they have been reeling in 10kg salmon regularly this season - and they are not exaggerating.
A Temuka Fishing and Outdoors spokeswoman said the good-sized fish had been caught in the Opihi, Orari and Rangitata rivers.
"I don't know why they're larger than previous years," she said.
Despite the great fishing she had not noticed any new anglers taking up the hobby.
Central South Island Fish and Game officer Mark Webb said there was no specific reason for the larger fish this season.
He suspects the Mckinnon Hatchery, on the lower Rangitata River, had made a positive impact on numbers as fish return for spawning.
Salmon have a life expectancy of about four years and in their final days they spawn in the headwaters of South Canterbury rivers.
Depending on what the fish fed on and their age would determine their size. Two-year-old salmon were between 3kg and 5kg, three-year-olds from 4kg to 8kg and four-year-olds up to 16kg.
It is likely there are higher numbers of mature salmon this year hence the greater chance of catching a big one.
Concern over phormidium, a potentially toxic algae in some rivers, did not affect the growth of the fish, Mr Webb said, but did affect the taste.
Warnings are in place at The Black Hole on the Waihao River, at Pareora Huts on the Pareora River and at Waipopo on the Opihi River.
The salmon season finishes at the end of March, while the coastal trout season goes until the end of April.
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