BC Hydro goes deep to restore huge, prehistoric sturgeon
On the Upper Columbia, hatchery-origin fish play a key interim role
The white sturgeon is a prehistoric fish that looks the part and captivates the imagination of the public, including anglers who put North America's largest freshwater fish on their bucket lists. It's also a source of awe and some frustration to those who have spent more than 15 years trying to recover wild white sturgeon stocks on the Columbia River in B.C.
The population of white sturgeon in the Canadian section of the Upper Columbia River was listed as endangered under the Canadian Species At Risk Act in 2006. The problem was ongoing "recruitment failure," where insufficient numbers of young white sturgeon survive to an age where they become reproductive and contribute to the next generation.
The wild white sturgeon population is trans-boundary, with about 1,000 in Canada and 2,000 in the U.S.
"We're doing a lot of research and monitoring to understand why recruitment failure is occurring," says James Crossman, BC Hydro's sturgeon lead and one of North America's leading experts on all things sturgeon. "Given the complicated life history of this species, it's a long-term investment. We don't have 20 years to learn why recruitment failure is happening and then solve it, because by then you've got a bunch of old fish that are potentially not reproducing.
"So in the interim, conservation aquaculture has been the main recovery measure to prevent extirpation and preserve the genetic diversity of the existing wild population."
On the surface, those recovery efforts led by BC Hydro have been incredibly successful. Where there were just over 3,000 sturgeon swimming in the Columbia River's Upper Basin 15 years ago, there are now more than 33,000.
But here's the hitch – 32,000 of those fish were bred in hatcheries, and we're still trying to solve the mystery of why recruitment failure is occurring.
A fish that can live 100 years and isn't picky about what it eats
Restoration of wild sturgeon recruitment is a longer-term and Herculean quest. The very things that make North America's largest and oldest freshwater fish wonderfully unique also pose enormous challenges for recovery initiatives.
White sturgeon aren't just giant fish that grow up to three metres or longer. They've been "around forever" and act like they know it, a fish that can live 100 years, isn't picky about what it eats, and is in no hurry to do anything, including spawning.
They don't spawn until later in life (20 years or more), and when they do start to reproduce, they don't spawn every year. Males spawn every 1 to 2 years, and females every 3 to 7. The time between spawning can vary depending on environmental conditions (e.g. food abundance) and the age of the fish.
The sturgeon's unique life history strategy has helped it adapt to changing conditions over thousands of years, but it poses challenges to today's recovery efforts. It can be a few decades before we fully understand how well our recovery efforts have worked, and this lag time in learning can make managing a population very difficult.
The Upper Columbia White Sturgeon Recovery Initiative (UCWSRI) was formed in 2001 by BC Hydro and two dozen other partners from government, First Nations, industry, and environmental groups in both Canada and the U.S. This collaborative approach serves to coordinate and implement conservation and recovery activities, and it offers scientifically sound recovery advice to government and non-government agencies.
The group assembles the best information and identifies gaps in understanding to help wild populations bounce back from a variety of challenges, including flow changes caused by the introduction of dams built from the 1960s through the 1980s.
"All 27 species of sturgeon world-wide are in some state of flux, either numerically depressed or having issues like we're having here, issues related to recruitment," says Crossman, who is Canadian chair of the recovery initiative. "Having this focused multi-stakeholder recovery team really helps facilitate progress toward the ultimate goal, which is recovery of the species," says Crossman, who is Canadian chair of the recovery initiative.
The amazing class of 2006, and other sturgeon surprises
White sturgeon conservation aquaculture on the Upper Columbia had initially been based on approaches used for other fish species: selecting wild mating females and males and transporting them to hatcheries, where they were spawned to produce offspring nurtured at the hatchery until large enough to survive in the wild.
"The fish from the hatchery have done tremendously well, better than originally predicted," says Crossman. "Right now we're estimating that there are about 32,000 hatchery-origin fish at large in this population – from Hugh Keenleyside Dam at Castlegar down to Grand Coulee Dam in the U.S."
Survival rates for hatchery-origin sturgeon depend on a variety of factors, and as new information was learned, the program gradually adjusted the numbers and sizes of hatchery fish that were released each year. But in the last few years, the recovery initiative discovered something that has led to dramatic changes to the aquaculture strategy: certain years, and certain families of sturgeon, were surviving at much higher rates than others.
"Fish released in the early years of the program have survived best, and a lot of that is due to the size the fish were released at," says Crossman. "In 2007, for example, fish released on the U.S. side were really large and those fish have done tremendously well – like 95% survival. We estimate that year class in itself is almost three times larger than the entire wild population."
In some year classes, 80% to 90% of the fish still surviving in the wild are from few adults that were spawned at the hatchery, and this high abundance of related individuals is cause for concern. In-breeding in fish, as in mammals, can cause health and survival issues down the road, so the program researched ways to increase the genetic diversity of hatchery fish.
The fish from the hatchery have done tremendously well, better than originally predicted
One of these ways was taking advantage of the existing wild adult sturgeon still spawning in the river. Crossman's team goes to select locations – such as below Waneta Dam near Trail – and sets equipment that catch fertilized eggs, fertilized by natural mate pairings, in the river. Those eggs are put in incubators in a portable trailer, where each tank receives river water with natural chemistry and temperature – for seven to 10 days before being transported to the hatchery.
This research was conducted by former Michigan State University graduate student Katy Jay, who now works for BC Hydro.
"What we found was that by collecting wild eggs and larvae, we could represent more wild adults in a single year than we could in 13 years of bringing adults to the hatchery," says Jay. "Because of these results, we've shifted entirely to that."
The program is also stocking Arrow Lakes Reservoir annually with hatchery-origin white sturgeon, to evaluate if a subpopulation could exist there and as an insurance strategy in case something catastrophic were to happen to the Upper Columbia sturgeon. This past May, the public was invited to help release about 1,800 juvenile sturgeon – each weighing about 300 grams – into Arrow Lake at Revelstoke."
The question remains: why aren't wild stocks thriving?
It's not that those 1,000 endangered wild sturgeon aren't spawning. The problem is that their offspring rarely survive past the first year and reach maturity, which is necessary for the next generation of wild stocks to thrive.
"You can have up to a couple hundred adults spawning each year," says Crossman. "And we see the eggs survive to hatch. They hatch with a yolk-sac and they hide and live off those yolk reserves for a couple weeks. Then they disperse downstream to other rearing areas to feed.
"We know now that there are tens of thousands moving downstream but from that point, through that first year of life, we see virtually no survival."
There are several main hypotheses – but no certainty – around the wild stocks' inability to procreate successfully. One thing that's certain is that flows on the river have been dramatically altered by dams built for various reasons: hydroelectric generation in B.C., storage for U.S. dams downriver as part of the Columbia River Treaty, and for flood control.
Dams have changed flows in the spring runoff – known as the "freshet" – and that could be key as sturgeon spawn in a narrow time frame at the peak or tail of the spring freshet. Another factor could be that the dams have dramatically reduced the murkiness of the water – today's Columbia is far clearer than ever, so it's more difficult for young fish to hide from predators.
There are also a greater variety of fish in the system, with introduced and/or invasive species – including walleye, northern pike and smallmouth bass – now sharing the waters (and also preying on young fish ) with the sturgeon and trout.
"It could also be that there's not enough food, or the right kind of food, at the right time for the young sturgeon," says Crossman, explaining that traditional dispersal of the young sturgeon likely took them farther down the Columbia in search of food than is now possible with the formation of Lake Roosevelt by the Grand Coulee Dam in Washington State.
You can't fish for Upper Columbia sturgeon, which are protected in B.C.
The sturgeon you may buy at the fish market or order at an upscale restaurant is farmed. Since 1994, commercial and sport harvests of sturgeon in B.C. were closed, and First Nations people voluntarily stopped their sustenance harvest.
There's now a catch-and-release sport fishery for white sturgeon on the middle and lower Fraser River. And there's no legal fishing at all for the sturgeon on the Canadian side of the Upper Columbia River, as the population is listed as endangered.
That doesn't mean, however, that anglers in the Upper Columbia never hook into the massive fish.
BC Hydro has been one of the leaders working towards sturgeon recovery in North America
Losses of the large, wild sturgeon by accidental "bycatch" are limited, as they're a hardy fish that in most cases will immediately snap the lines of anglers fishing with bait for much smaller fish, such as walleye. But there is significant bycatch of the smaller, hatchery-origin sturgeon, and Crossman says some fishers aren't pleased when they lose fishing gear or that they're not allowed to fish for what is now a fairly abundant population of larger hatchery fish.
"We've received feedback from anglers who have encountered a significant number of sturgeon in recent years," he says. "Many are concerned about there being too many hatchery-origin sturgeon, and we are working with management agencies in BC to ensure we are working towards a target abundance for the population that is supported by good science."
There's a limited fishery in the Columbia on the U.S. side of the border, where the population is not listed, in part to reduce stocks of certain dominant families of hatchery-origin sturgeon. That's a conservation measure being considered in B.C., but given the endangered status in Canada is much more challenging to implement.
Crossman can understand why people want to see sturgeon. The biggest one he has seen on the water was a 400-plus-pound Atlantic sturgeon that was over 10 feet long. On the Upper Columbia, the biggest his team has handled was about nine feet long and 300 pounds.
"Sturgeon will breach or jump, so if you're on the river in the early evening, you might catch a glimpse of a sturgeon breaking the surface of the water," he says. "We don't know exactly why they jump – they might have a parasite on them like a little leech. Or they're chasing a fish to eat through the water column."
'We're on the right path'
It took quite a while for fisheries agencies to realize that the white sturgeon were in trouble, in part because even with declining stocks, the long-living and large species were still being spotted. "So they seem present – no one really realized there were a lot of issues until research and monitoring began in the mid-nineties," says Crossman.
Even 15 years in, Crossman says the recovery initiative is still learning new information about the population and the species, which emphasizes the need for the recovery initiative to remain adaptable. It's a long-term initiative that Crossman says will outlast his position as chair, or perhaps even his lifetime.
"They're a fascinating fish that live a long time, take a long time to mature – and when they do mature, don't reproduce every single year," he says. "We've been on the right path and we've learned a tremendous amount. Importantly, sharing information we've learned, and incorporating learnings from work on other species, has really helped facilitate recovery programs world-wide.
"I think there's also a big takeaway from all the work BC Hydro has done over the years. It has been one of the leaders working towards sturgeon recovery in North America."