Salmon – Forecasts vs Returns

Unfortunately there’s something of a theme developing with several major salmon stocks on the BC south coast this summer. I’ve used the word unfortunately as the descriptive qualifier because the theme is salmon returns failing to meet pre-season expectations, in fact not even coming close.

The first salmon stock to be downgraded were the chinook returning to Nootka Sound, where the estimate of abundance in the terminal area adjacent to the Conuma River is now just over 20,000 fish compared to the pre-season forecast of 80,000 chinooks. Twenty thousand chinook is still a substantial number and not a conservation concern for the watershed, indeed the terminal area commercial gillnet fishery will be proceeding later this week, but the real question is why the return is so much less than expected.

In some respects an annual forecast for a chinook stock should have the greatest reliability of any salmon species because of the multi-age composition comprising a single spawning year-class. With few exceptions the greatest variability in salmon returns is dependent on how an age-class did in its early marine life stage. Once the fish are a couple of years old they are very robust in comparison and there is usually a strong relationship between the returns of age 2 and 3 chinook and those returning in subsequent years which makes this years much lower than expected return to date so puzzling. It could be that there are more fish yet to arrive but Conuma chinook have a fairly early run timing compared to many other WCVI origin chinook so this outcome seems unlikely.

The forecast return was said to be the highest in many years, dating back to the early 1980’s, however I’d have to say that my own fishing experience out of nearby Kyuquot doesn’t suggest strong waves of chinook migrating through the near shore area. Fishing there has been decent but nothing out of the ordinary.

One of the interesting features of chinook management in the Nootka terminal area is that the estimate of abundance in-season is derived from the recreational CPUE (catch per unit of effort, i.e. number of fish per boat trip). Some years ago DFO staff recognized that there appeared to be a consistent relationship between recreational CPUE and the run-size and this methodology has been both peer reviewed and subsequently used. I’m not aware of another place using any salmon species where this approach is used.

So it’ll be interesting to see whether the later returns to rivers such as the Stamp and Nitnat follow the same pattern or if Conuma is unique. The other thing to look for from spawning ground information will be the ratio of males to females – last year the balance was badly skewed, with many more male than female chinook salmon in the mix. This too is something of a puzzle although the assessment of so many younger, overwhelmingly male chinook last year was the basis of the 2016 pre-season forecast.

Changing species to Fraser River sockeye, the 2016 return thus far is a fraction of the pre-season forecast, with some DFO staff characterizing it as the worst ever. The summer run-timing group, which was expected to provide the majority of the aggregate (all run-timing groups) return this year, is now assessed at 600,000 fish compared to a pre-season 50% probability forecast (a one in two chance of meeting or exceeding that number) of 1.7 million. For comparison, the mean run size of this cycle year (sockeye “management speak” based on the dominant age-4 at maturity characteristic of most sockeye) is 2.6 million fish. The Chilko River is the dominant contributor to the summer run-timing group, in combination with smaller runs to the Stellako, Harrison and Stuart rivers.

Given the very warm conditions of the northeast Pacific Ocean over the past couple of years and the open ocean marine life history of sockeye I suppose this low return shouldn’t be entirely unexpected. However several other south coast sockeye stocks such as the Stamp/Somass and the Columbia River aggregate, which includes Canadian sockeye from the Okanagan River – DFO has just opened a recreational sockeye fishery in Osooyos Lake for goodness sake! – have done quite well so why Fraser summer-run sockeye have been so badly impacted is another puzzle. As well, although a small component of the overall Fraser return this year the late run timing group to date has been assessed with a return slightly above the 50%probability forecast.

The result is that DFO has closed sockeye food fishing for First Nations in both the marine approach waters and in the Fraser River itself, which is unwelcome news for them and may have implications for the broader recreational fishery should chinook be required as a substitute. One certain outcome is that with such a low return even with the best of environmental conditions it will take a number of cycle years to rebuild this run, meaning that commercial and recreational fishing for Fraser sockeye in 2020 and 2024 are most unlikely to occur.

Meanwhile the summer fishery for other salmon species continues. In Campbell River the focus of attention has shifted into the lower straits above town where some good or better chinook fishing is taking place. The river mouth chinook fishery hasn’t really taken off yet with only one fish registered by the Tyee Club at the time of writing but that should kick into gear now. As noted earlier there’s productive chinook fishing to be had on WCVI even if it isn’t quite what was hoped for. Big fish can be encountered anywhere in mid-August, even when you’re not fishing for them – tight lines!