Malcolm Bell, from The Complete Angler fishing tackle store in Christchurch, recently broadcast a question and answer session with Rasmus Gabrielsson about the poor state of the Canterbury salmon fishery. Rasmus Gabrielsson is a fisheries scientist with the Cawthron Institute in Nelson. Although they didn’t cover any new ground the interview was both interesting and informative.
Gabrielsson did, however, give a clearer picture of where current scientific thinking rests on the subject. Where once the emphasis was on enhancing the salmon fishery by introducing huge numbers of hatchery-reared smolt, which isn’t really financially viable, to nowadays looking at smarter ways of doing things. I want to emphasize that this is my interpretation of the interview rather than a word for word account.
Many younger salmon anglers will have heard us older blokes talking about the glory days of salmon fishing back in the late 70s to mid-90s when a small salmon was any fish weighing less than 20 pounds. Amazingly by today’s standards, 30 lb + fish were quite common.
Also in those days far greater numbers of salmon were being caught by anglers. For example, on Waitangi Day 1996, there were at least 200 salmon caught in the surf at the mouth of the Rakaia River alone. Many of these fish weighed over 30 pounds. So what happened? Where did all the salmon go? Why did all the big fish disappear?
From the late 70s to the mid 90s commercial interests set about enhancing the salmon fishery. The intention was to produce huge numbers of salmon on an industrial scale for sale around the world, fresh, frozen, and canned.
Hatchery capacities were stepped up considerably and enormous numbers of pacific salmon smolt were released into our East Coast braided rivers. By the early 1990s, it had become clear that this just wasn’t commercially viable.
During that 20 year period, an incredible 50 million salmon smolt were raised in hatcheries and released into the wild. In just one year alone 6 million smolts were released in Canterbury. By the 1996-1997 and 1997-1998 seasons, the numbers of returning salmon had dropped off dramatically. There were suddenly fewer salmon returning and those that did come back were noticeably smaller than before.
Back in the heyday of the late 70s to the mid-90s, there were as many as 25,000 salmon spawning in the main East Coast rivers, whereas today spawning numbers are in the low thousands.
Rasmus sights two main reasons for this happening. Firstly up until the mid-90s, there had been very good salmon survival rates at sea. From 1996 onwards into the 2000s conditions for the salmon at sea have been poor. Interestingly the less than ideal sea conditions caused by higher water temperatures and less food for the salmon to eat haven’t just been the case for New Zealand but have been the same in other countries as well. The
During the bumper, big fish returns up to and including the 95-96 season, there was a broader salmon age range This was also true earlier during the late 50s and 60s. When we had a wider age range among returning fish, there were a lot of 3-year-olds, and large 4-year-olds made up as much as 10 to 20 per cent of the fish entering the rivers to breed. There were fewer small 2-year-old fish returning from the sea.
In other words during the bumper years, the returning salmon were older. Having spent another year feeding at sea they were obviously going to grow bigger. Here is a photograph of a monster salmon caught in early January 1995 in the Waitaki River by Alan Pratt. It weighed in at 18.6 kg (41 pounds). Today the picture has changed considerably. Most of the salmon returning to the rivers to breed are 3-year-olds, with as many as 30% being smaller 2-year-olds. It is now rare to encounter a 4-year-old salmon.
The salmon are just not staying in the sea long enough to grow as big as they did in the past. We are now regularly seeing kingfish and other warmer water sea fish species being caught along the Canterbury Coast. Warmer sea conditions are not good for salmon. Rasmus Gabrielsson noted that some of the smaller East Coast rivers, along with the West Coast rivers, haven’t been interfered with to the same extent as the big East Coast Rivers like the Rakaia and the Waimakariri where enormous smolt releases took place prior to 1995 intended to pave the way for massive ocean ranching.
Pacific salmon are an amazing species quick to make local adaptation through natural selection. Within just one or two generations salmon can adapt to changing conditions. Massive commercial releases of hatchery fish interbreed with wild fish and destabilize the core populations of salmon. The previously stable population of wild salmon may have simply been overwhelmed by the sheer volume of hatchery fish to the detriment of the fishery as a whole.
Bigger 4-year-olds produce more eggs. The eggs are also bigger providing more nutrient and hence the offspring are more likely to survive. Here is another monster salmon caught “back in the day” prior to 1996 by Norm Thackwell in the Waimakariri River. It weighed an astonishing 42lbs.
Rasmus Gabrielsson believes it could be a good idea for anglers to release the bigger older fish particularly the females. Though catch & release causes stress and exhausts returning salmon decreasing their chances of survival. The greater the number of older salmon that make it through to spawn the better it will be for the fishery’s recovery.
Salmon are very adaptable. Provided there are favourable conditions at sea the fishery will likely right itself eventually. Salmon smolt releases into lakes are much more effective because mortality rates are significantly lower than they are at sea.
He noted that the sockeye salmon fishery in South Canterbury and North Otago had up until a few years ago all but disappeared but has now come back very strongly with a population thought to number some 40,000 fish. Now there is a good challenge for you. Why not set about catching a sockeye salmon.
I strongly suggest you watch Malcolm Bell and Rasmus Gabrielsson on The Complete Angler podcast below. You also might like to take a look at this article which appeared on Stuff.co.nz recently: Sea-run salmon crisis prompt daily bag limit change.
Rasmus Gabrielsson is now Chief Executive of North Canterbury Fish and Game.
Fishing Matters #01 – Rasmus Gabrielsson and Malcolm Bell (Salmon Fishing NZ, Fishery Science).
This post was last modified on 10/02/2021 3:46 am
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