The decline of the South Island salmon fishery is widely believed to have been caused by a range of environmental factors that have gotten worse over the past 20 years. These include degradation of headwater streams from more intensive farming, too much water is taken from our rivers for agriculture, underground aquifers being depleted for irrigation, fertilizer runoff, dirty dairying practices, poor feeding conditions at sea, fish screens not doing their job properly, genetic factors caused by large scale smolt releases weakening the adaptability of wild stock, and anglers catching too many salmon made worse as salmon numbers have become severely depleted. Let’s take a look at the reasons behind the current demise of the fishery. Although this article is about poor salmon returns, many of the factors which affect salmon apply to trout and native fish too.
Here is a fairly typical example of the dairying practices that are damaging the salmon fishery Protesters demand accountability over ‘diabolical’ state of Canterbury rivers – Radio New Zealand.
This piece is not an attack on the farming sector. I acknowledge that there are many farmers who work tirelessly to be good neighbours and protect the environment. This video is an inspiring example of what can be achieved when we work together, Restoring Harts Creek (WET 2015). Let’s not waste energy pointing fingers. Instead, we must all work together to find solutions.
Rising water temperatures can cause all sorts of problems for salmon such as reduced reproductive rate, a reduction in the number of eggs that survive, delayed growth of fry and smolts, an increased likelihood of disease, a decrease in the ability of young salmon to compete with other species for food, and to avoid predation (Spence et al., 1996; McCullough, 1999).
Summertime low flows are made worse by excessive water abstraction from our east coast rivers, causing trout and salmon populations to become stressed as a result of less space, lower oxygen levels, higher water temperatures, reduced food supply and greater predation.
When river levels drop very low the water heats up to dangerous temperatures over 22°C making it difficult for juvenile salmon to survive the first stage of their lives as they make their way to the sea. Studies overseas have shown that juvenile salmon can stand a wider range of temperatures than adult fish. However, river temperatures in the low 20s are likely to be fatal.
The failure of fish screens to prevent the needless destruction of a substantial percentage of salmon fry is nothing new. It is continuing unabated. Here are two quotes from MAF’s own publication 35 years ago and refers only to the Waitaki River catchment. The same thing has been going on for decades made worse as more water consents have been granted.
“Such levels of abstraction, together with an absence of fish screens on any of the intakes, have undoubtedly lessened the fisheries value of such tributaries. It has been estimated that between 30% and 80% of downstream migrating juveniles (mostly rainbow trout) are lost down irrigation races each season from the Maerewhenua River, which together with the Hakataramea River, are the only known spawning areas for rainbow trout in the lower Waitaki catchment.”
The piece goes on to say, “Apart from a rotary fish screen on the intake of a private water race taking water from the Waitaki River below Hakataramea, there are only a small number of fish screens of limited effectiveness throughout the region. Unknown numbers of quinnat salmon juveniles are lost down irrigation races originating from the Waitaki River.”
“Observations on the Rangitata Diversion Race by FRD (Fisheries Research Division) indicate that considerable numbers of small salmon become entrained within the system, and suggest that losses from the Waitaki may be of significance. Installation of effective fish screens, particularly on tributaries in the mid and lower catchment, should be a matter of high priority.” (Modifications to regional waterways Part IIV the Waitaki region – Freshwater Catch Winter 1985 No. 27).
It is scandalous that over three decades later this problem has still not been fixed. Why even waste money on concrete and steel building a fish screen if it doesn’t work? This is a failure of monumental proportions. Juvenile trout and salmon are still being diverted from our rivers and squirted out onto paddocks. Poor salmon returns for a period are one thing. Salmon anglers worry that the fishery will collapse altogether.
Returning to more recent times, “All 32 fish screens installed in irrigation schemes throughout Canterbury monitored by Environment Canterbury (ECan) were found to be non-compliant.” “ECan estimates there are more than 900 sites with fish screens throughout Canterbury. Of those, there are an estimated 400 throughout South Canterbury.” These are quotes from a piece by Matthew Littlewood on Stuff.co.nz dated 3 March 2020.
The enormous cost of constructing effective new fish screens, or making existing screens compliant, suggests that this issue isn’t going away anytime soon. The design of fish screens should enable migrating and resident fish, safe passage past the structure. According to a report by Fish & Game Officer Steve Terry, “Even on screened intakes (e.g. Amuri scheme), fish rescue operations yield in excess of 1,000 sports fish each year”.
Salmon fishing has been an important part of the culture in Canterbury for generations. A big Rakaia River fish from the 1990s. Salmon has never been exactly easy to catch. Any day you get one is a red-letter day!
The extent to which the Quinnat salmon fishery on the South Island’s east coast has declined is difficult for many younger anglers to fully appreciate. In 1985, over the four days of the Waitaki Salmon Fishing Competition, held from 8-11 March, 754 salmon were caught. There were 227 caught on Friday, 130 on Saturday, another 227 were taken on Sunday, followed by another 170 on Monday by a total of 664 anglers. The heaviest fish weighed 15.6kg (34.4 pounds), the second heaviest fish weighed 14.40kg (31.7 pounds), and the third 13.85kg (30.5 pounds).
There was a total of 35 limit bags taken – a limit bag back then was four salmon per angler per day. Many of the limit bags were taken from jetboats that went out through the mouth to fish within the 500m radius of the river entrance. We would probably now regard angler successes on this scale as wanton gluttony. It was a very good salmon season that year. Keep in mind that the wild salmon fishery has always fluctuated in terms of size and numbers of fish returning. It has fluctuated between boom and bust before. Poor salmon returns for a couple of seasons isn’t new.
The 1985 Waitaki Salmon fishing Competition came at a time when commercial enterprises were releasing large numbers of smolt for their ranching operations along the Canterbury coast. By the mid-1990s salmon farming operators realized that the numbers of mature salmon returning to them from the sea expressed as a percentage of smolt released was just too low for their businesses to be viable, so they gave up on the idea.
“Early returns were dismal – only 15 fish from the first liberation of nearly a million fry.” “Between 1984 and 1990, Tentburn released 25 million fish into the Rakaia, but, despite initial optimism, ocean-ranching returns turned out to be consistently poor, with a mean survival rate of 0.2–0.6 per cent. One by one the salmon businesses were forced to close shop, and by 1991 all large-scale releases had been abandoned.” (Derek Grzelewski – Salmon the Miracle Fish, May-June 2003, NZ Geographic).
Salmon farmers could see that it made more commercial sense to not release the salmon at all and to instead grow them in captivity in cages to a marketable size if poor salmon returns were going to persist. The salmon farms in the Mackenzie Country canals have ideal conditions for raising quinnat salmon. In mid-winter, the water in the canals doesn’t usually drop below 6°C despite the air temperature getting down to as low as -10°C. At this low temperature, the salmon grow at a slower rate. During high summer the air temperatures can rise above 30°C but the water in the canals remains at a constant 15-16°C which is the optimal temperature for salmon growth (Swimming Upstream – How Salmon Farming Developed in New Zealand by Jennifer Haworth). It is worth mentioning that the canals don’t run dry and the cold mountain water is unpolluted!
Ocean ranching of salmon in sea cages also makes more commercial sense than releasing them to mature naturally in the wild and hoping for a viable percentage return. However, warming sea temperatures and insufficient tidal flow rates have caused major problems for salmon farmers in the Marlborough Sounds. Unlike humans, salmon cannot self-regulate their body temperature through perspiration. Once sea temperatures climb above 16°C the fish become stressed. By the time the surrounding water temperature reaches 19°C degrees or more the salmon start dying in the sea cages in big numbers.
The recent one-day Rangers Salmon Fishing Competition was held on 31 March 2021 at the mouth of the Waimakariri River, with 130 anglers fishing, unfortunately, failed to produce any salmon at all. I’ve never seen that before. Here is a youtube video of the prizegiving. It shows the comradery and social nature of many Canterbury salmon anglers.
The same thing happened with the Otago Harbour Salmon Fishing Competition earlier this year when for the second time since 2013, over 200 anglers were unable to catch a single salmon between them, albeit one undersized fish was caught, photographed and released. These results are very much in keeping with the decline of the fishery overall. Otago Harbour Salmon Fishing.
Salmon anglers who previously would catch fish every year have been catching nothing. The reported angler catch rate has dropped to a very low level. The salmon that are caught are all small fish compared with 25 years ago.
What is of particular significance is that whatever the problem is causing the big drop in salmon size and numbers, it exists from the Hurunui River all the way down to the Otago Peninsula. The elephant in the room is rising sea temperatures. As we can see from the experience of salmon farmers operating sea cages it only takes the water to heat up by a few extra degrees over optimum during summer and the salmon start to become very unhappy!
McCullough (1999) found that adult chinook salmon and steelhead (rainbow trout) die at temperatures of 21-22°C in the Columbia River. Upstream migration ceased at temperatures over 20° C. Bell (1986). McCullough (1999) also noted that egg size and development was substantially altered when adults were exposed to temperatures over 17.5° C.
There is considerable anecdotal evidence to support the theory that rising sea temperatures are at the heart of the decline of Canterbury’s once magnificent salmon fishery.
Over the past 100 years, Quinnat salmon have never established themselves in the North Island of New Zealand. There were some small-scale attempts to release salmon fry in the Hutt River each year from 1876 to 1878. However, there have been no full-scale attempts to do so in a similar fashion to that carried out by Lake Ayson in the South Island in the early years of the 20th century.
The odd salmon has been caught in the North Island in the Rangitikei River and Lake Onoke. In early February 1980, George Kerehoma caught a 7.7kg (17 pounds) Quinnat jack salmon in a net at the upper end of Lake Onoke in the Wairarapa. There have also been other very occasional confirmed cases of salmon being caught in the North Island. Conditions there are unfavourable. Most likely the sea and river temperatures are too warm for them. Though river topography may also play a part.
That salmon have not become established in the North Island may be an indicator that even slightly higher sea temperatures off the South Island’s east coast may well be shifting the equation from ideal to marginal adding to the problem of poor salmon returns. Sea temperatures here in New Zealand have always been warmer than where the salmon originated from in their native North America.
The elephant in the room, rising sea temperatures, has seen snapper, and in particular yellowtail kingfish now being caught much further south than was previously the case. Although we have experienced poor salmon returns, kingfish have actually become quite plentiful around the Otago Peninsula. Commercial fishermen report that kingfish numbers have increased ten-fold in Otago waters in the last ten years. Global warming is a worldwide problem that will require a worldwide solution.
University of Otago marine ecologist Prof Steve Wing said the fish (kingfish) were becoming more prevalent in southern New Zealand because the water was getting warmer. Coastal water temperatures were between 2degC and more than 6degC above average at the moment (January 2018), according to a report in the Otago Daily Times by John Lewis – Kingfish in harbour climate ‘sentinels’.
Catching Kingfish in Otago Harbour was a rare event. But has now become more common. The same applies around the Banks Peninsula. To fish for kingfish realistically requires a boat, so they are not going to take the place of salmon in the hearts of Canterbury’s legions of salmon anglers. One of the great things about salmon fishing is/was that it was close at hand. You could fish early in the morning (the best time) or after work on the way home.
A female salmon lays around 5,000 eggs in a headwaters stream in a nest called a redd. Of these, only three or four will live to maturity at sea, evade predators, and successfully make the return journey to complete the cycle of life. With a survival rate that low it isn’t going to take a heck of a lot going wrong before the salmon fishery is in serious trouble. As we have seen lots of things have been going wrong! Quinnat salmon return from the sea in New Zealand between 2 and 4 years of age. There is a lag therefore between positive action being taken and actually increased returns.
Going back to the early to mid-1990s fisheries scientists estimated as many as 37,000 salmon would run up Canterbury’s braided rivers each year on average. However, according to Ross Millichamp a former manager of North Canterbury Fish and Game, “the total run may fluctuate between 10,000 and 75,000 fish, of which anglers catch around 35-40 per cent. In the Rakaia River runs have varied from 1,500 to 22,000 fish.” The runs have always been variable. There have been periods of poor salmon returns in the past. At the start of every season, there is always great speculation among anglers about how big the run will be. There is a good chance that with resolute sustained effort and luck those days will come again.
There are a small number of dedicated salmon anglers in Canterbury who are working tirelessly to preserve the fishery by river enhancement projects, volunteering at hatcheries, fin clipping, and so on to help keep the fishery viable. Their efforts are commendable and hopefully will go some way to restoring the salmon fishery to its former glory.
Fish and Game have reduced the salmon bag limit to one a day and shortened the fishing season to the end of March instead of the end of April, in the hope of preserving the remaining salmon to at least keep the fishery ticking over. North Canterbury Fish & Game is encouraging salmon anglers to limit their seasonal catch to four salmon. This is nowhere near as bad as it sounds. The vast majority of licence holders who fish for salmon catch either one or none in a season.
Many salmon anglers will be unaware that Fish and Game does a lot of sterling work behind the scenes managing various stream restoration schemes, particularly in the high country. Fish and Game staff work with landowners to improve fencing out stock, planting natives, and weed control. In these hydra waters, salmon spawn and the next generation start before beginning their journey to the sea.
Unfortunately, the only aspect of the salmon fishery Fish and Game have control over is the angler regulations. That too much water is being extracted from our rivers, fertilizer runoff, fish screens not working and the like are outside their control. Such things can only be changed by Environment Canterbury (ECan). To those involved in the farming sector reading this, if you own one of the 900 fish screens in Canterbury it is time to be a good neighbour and fix it if you haven’t already. Surely, there is enough engineering expertise in the region to modify these screens so that trout and salmon fry and fingerlings don’t become stranded on the “wrong side of the fence?”
Salmon need cold, clear, unpolluted waters to reproduce. Therefore salmon are good indicators of the watershed and environmental health.
Let me leave you with this gem from the late Slim Dusty. “But there’s-a nothing so lonesome, morbid or drear, than to stand in the bar of a pub with no beer”. Except that is for Canterbury salmon rivers with no salmon in them.
We nearly had a second sea-run salmon species in New Zealand, the sockeye salmon (updated).
In the United States
Here are links to two articles about the decline of the salmon fishery in the United States. The first is about Washington state’s mighty Snake River, where once the salmon runs were so enormous they defied belief. Of particular interest to us here in New Zealand is what the authorities are doing, or considering doing, to save the salmon runs from extinction. Salmon face extinction throughout the US west. Blame these four dams.
The second link is to an article entitled US allows killing of hundreds of sea lions to save struggling salmon. How nutty is that? The sea lions were of course present over 100 years ago at the height of the once-massive salmon runs. According to conservative estimates, the Columbia River Basin, both above and below Bonneville Dam, once produced between 10 and 16 million salmon annually. Source, Columbia River Inter-Tribal Fish Commission Columbia Basin Salmonids.
This post was last modified on 05/11/2021 10:15 pm
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