Guest Commentary by Rex N Gibson
It was like that line from the Ancient Mariner. “There were salmon, salmon, everywhere but not a fish to catch”. I conservatively estimate that there were a thousand salmon jostling for partners in a pool area of about 100 metres. No it was not 1996 l. It was March 2026. I have never seen such a freshwater schooling event before.
They were beautifully coloured sockeye salmon (Onchorhynchus nerka) and the location was just up from the mouth of the Twizel/Ohau River which empties into Lake Benmore across several braids. The sockeyes red and pink colourations are quite attractive. Other anglers assured me that there were sockeye salmon all the way up the river, including past the road bridge on State Highway 8. These fish average about one kilogram. With Lake Benmore as their ocean, rather than the Pacific Ocean, they do not reach the 4-7 kg sizes recorded for sockeyes in their American homeland. In North America they are considered a popular table fish and have bright orange flesh.
Their numbers in the Waitaki catchment have exploded over the last twenty years. Originally released in 1902 from a single release, their ancestors ran down the Ohau and Waitaki Rivers to the Pacific Ocean as fingerlings. They then returned as sizable fish to spawn in the Ohau region. Then along came the hydro dams; Waitaki (Kurow) in 1930 and the Aviemore, Benmore, Ruataniwha, etc. in the 1960s and 70s. The fish ladder built at the Waitaki dam was not successful. For decades it was believed that the sockeyes were extinct. Years later, around 1982, a remnant population was found in a tributary above Lake Ohau. Without human assistance they have subsequently made their way into Lakes Ruataniwha and Benmore surviving the turbines of the power stations. The Twizel, Ahuriri and Tekapo rivers are now major spawning locations.
Despite the sockeye resurgence, anglers rarely catch them because they feed on zooplankton, and small invertebrates like daphnia, and don’t usually take a fishing lure. Fish and Game warn that It is an offence under the Conservation Act to disturb spawning salmon – you can’t catch, net or spear the fish, or even walk in the river bed and trample their redds, or nests.” Central South Island F&G have published various articles about targeting sockeyes in Lake Benmore. Devising methods of capture however is still a work in progress. As they spawn much earlier in the year than trout the fishing season for sockeyes finishes at the end of February.
On my recent trip I skirted around the river delta to fish the Benmore edge and the area out from the Tekapo Mouth. Whilst blind casting I hooked a solitary sockeye on a nymph. It was quite acrobatic before I managed to get it in and release it. There were a few small schools off the Tekapo Mouth but nothing like the populations that were in the river. The rumour is that the spawning fish taste is unpleasant. Whether that is true or a myth circulated to discourage harvesting I am unsure.
The lower Twizel had excellent populations of bullies so the bullies were clearly unfazed by the sockeye invasion. There were also moderate numbers of trout around the lake edge. It is suggested in some articles that the young of the sockeye provide a great food source for Benmore’s trout and salmon.
Last year I wandered the lake edge and was initially disturbed by the scores of fish carcasses I was encountering. I soon realised that they were of course sockeyes that had spawned. Unlike trout they die after the spawning act is complete. In the rivers they slowly waft around “waiting for god” for a week or so before allowing the current to take them away. Many of the spent fish have developed fungal infections on their skin giving them a technicolour appearance. In years gone by I used to observe similar sights around the mouth of the Hakataramea River when Chinook/King/Quinnat salmon spawned. It was fascinating to watch rainbow trout circulating among the spawning salmon catching any stray eggs that the salmon failed to cover. It was impossible to interest the trout in anything from my fly box when they had salmon caviar.
I recall the Principal of the local school telling me that her classes made an annual trip to observe the salmon. Sadly it is no longer a spectacle there.
Spent sockeyes washed out to the lake fringe
F&G have published this link below of the spawning. https://www.youtube.com/watch?v=taOmafdHGcY
Rex N Gibson
Stories like this remind us that fisheries management must be system-specific. What thrives in a hydro-lake environment may not translate to braided East Coast rivers dependent on ocean survival. We need to understand those differences before drawing simplistic conclusions about “salmon recovery.”
There’s something bittersweet in reading about school trips once centred on salmon runs that are no longer spectacles in other rivers. Perhaps the Waitaki sockeye offer an opportunity for renewed community engagement - not just as a fishery, but as a living ecological classroom.
The description of trout feeding on stray salmon eggs is particularly telling. These interconnected food webs often go unseen, yet they underpin lake productivity. The sockeye may be contributing more to the wider Benmore ecosystem than many realise.
It’s extraordinary to think that a species presumed extinct in the system half a century ago has re-established itself without deliberate restocking. That persistence through dams and turbines challenges a lot of assumptions about total system loss. Thank you for documenting something many anglers may never witness.
The contrast between the sockeye resurgence and the collapse of some sea-run Chinook stocks elsewhere is striking. It highlights how life history strategy matters. A lake-based system insulated from marine variability appears to offer stability that ocean-dependent runs cannot rely on. There are lessons here for how we think about habitat security and long-term fisheries resilience.
What a remarkable account. The sockeye story in the Waitaki system is one of those quiet ecological surprises that doesn’t fit the usual narrative of decline. It’s a reminder that while human modification can be destructive, biological systems sometimes adapt in unexpected ways. That doesn’t diminish the need for good management - but it does underline the resilience built into nature when given even a narrow pathway.
Ha! Ha! AI has it wrong when it says “While the Hakataramea river is historically famous for salmon, today it is more commonly noted by Fish & Game New Zealand as a destination for brown and rainbow trout. The salmon run remains an important ecological feature, though it can be heavily affected by low river levels.”
The salmon run is no longer because of dams. Even if fish ladders are put in they’re mostly poorly sited and don’t work.
As the article says “sadly” the Hakataramea is no longer accessible to sea run fish.