Marine heatwave: Salmon declining in Dunedin as water warms, hatchery closes

Fishing for salmon has been a popular pastime in Otago Harbour for decades. Photo / Otago Daily Times

Warming waters and the closure of a hatchery mean the days of catching salmon in Otago Harbour are likely coming to an end.

Otago Salmon Anglers Association president Colin Williams said the declining salmon numbers meant it would no longer be running its annual salmon fishing competition.

The number of salmon in the harbour had already been in decline before it was announced in September the Dunedin Community Salmon Trust hatchery was closing.

The competition was last held last year, and not one salmon above the minimum weight limit was caught. This year’s event was cancelled because of Covid-19 concerns.

Salmon were not coming back up the harbour because of the rising temperatures, Williams said.

“Fishers on the wharves aren’t catching fish the way they used to.”

The Otago Salmon Anglers Association, along with the Dunedin Community Salmon Trust, had been regularly releasing smolt into the harbour to sustain a fishery population, but the impending closure of the hatchery that supplied the smolt marked an end to restocking efforts.

It did not look like anything could be done to preserve salmon fishing in the harbour, Williams said.

The Dunedin Community Salmon Trust hatchery announced its closure in September because of regulation changes by the Ministry of Primary Industries requiring the tagging of hatchery-reared salmon.

When asked if fishers might still find the odd salmon without the regular smolt replenishments, trust chairman Steve Bennett yesterday said it was unclear.

“We did it for about 20-odd years to create a kind of fishery, but without it being topped up, I don’t know what’s going to happen.

“It’s a shame to see it discontinued,” Bennett said.

Otago Fish & Game Council chief executive Ian Hadland said while a very small amount of natural spawning was happening in the Water of Leith and Lindsay Creek, it was “not particularly successful”, and nowhere near enough to sustain a harbour fishery population.

Fish & Game’s efforts were concentrated on restoring a wild sea-run salmon fishery in the lower Clutha River, as the Otago Harbour was outside of its jurisdiction, Hadland said.

A recent report by the National Institute of Water and Atmospheric Research predicted water temperatures would be above average once again this summer, continuing a multi-year trend of summer marine heatwaves.

- ODT