A month or so ago, I had opportunity to screen the documentary, “Artifishal” (admittedly, a pretty clever title), in a room full of fish biologists, geneticists, and hatchery managers. The premise of the film is that both hatcheries and open pen aquaculture of salmonids are directly responsible for the decline of natural runs and if allowed to continue, will lead to extirpation of these species. Hoo boy. Talk about the air being sucked out of a room.
The conclusion the documentary comes to is extreme, but it does beg the question of the current consensus of how salmonid hatcheries impact their wild counterparts. Of course, the answer is “it’s complicated”, mostly because hatcheries are species-, ecosystem-, and goal-specific. Lumping all hatcheries into a monolithic group (and in the documentary, hatcheries were conflated with oceanic, open net pen aquaculture practices as well) fails to capture the nuances that exist between hatchery programs.
Salmonid hatcheries are employed for different reasons depending on the species and system: to provide harvest and so relieve fishing pressure on wild stocks, to recover wild stocks, or a combination of the two. Furthermore, hatchery fish often are managed as separate stocks from their wild counterparts with the intention of keeping them genetically separate. These fish are tagged and either caught by anglers or, upon returning, brought back into hatcheries to create the next generation of hatchery fish. Alternatively, some programs integrate wild fish into the production of hatchery stocks to prevent the propagation of a domesticated phenotype. Different hatchery programs have decreased short-term extinction risks for endangered populations, mitigated for habitat degradation and impediments, provided demographic boosts to existing populations, and re-introduced salmon into habitat from which they had been extirpated.
So what’s the latest on salmonid hatcheries? Unsurprisingly, it depends on the hatchery and species.
The recent development of parentage-based tagging (PBT) whereby hatchery-origin fish are genotyped across generations will allow for tracking of quantitative traits like reproductive success, disease resistance, run timing, and age at maturity. Such studies are ramping up now, especially in steelhead, chinook, sockeye, and coho salmon fisheries in the Pacific Northwest. For example, Evans et al (2019) reconstructed pedigrees of three full cohorts of chinook salmon from two river systems in Oregon and estimated heritibilities and evolvabilities of several fitness traits in both wild and hatchery populations.
Janowitz-Koch et al (2018) looked at a population of chinook salmon returning to Johnson Creek, Idaho over 16 years using pedigree information. They were able to track the reproductive success of natural-origin fish and those originating from a supplementation program. In this case, broodstock are created every generation by bringing natural-origin fish into captivity to spawn thereby preserving local adaptation. The authors found that the hatchery supplementation program provided a demographic boost to the population over two generations. When hatchery-origin fish spawned in the wild, they had a lower reproductive success than natural-origin fish, but when hatchery fish spawned with wild fish, the reproductive success of the offspring was similar to those with both wild parents. Also, origin (hatchery vs wild), return year, and body length were significant predictors of fitness.
Several studies over the past 30 years, mostly focused on Columbia river basin steelhead stocks, have suggested that natural-origin steelhead have a better survivorship than their hatchery counterparts and rivers with predominately hatchery-origin returns have a lower reproductive success than rivers dominated by wild returns. Studies on steelhead in the Hood River in Oregon from 2007 to 2012 showed that even a single generation of hatchery rearing could significantly reduce the survival and reproductive success of fish in the wild. Notably, other similar studies on chinook salmon failed to document such marked declines of reproductive success. However, even as hatcheries produced huge numbers of salmon, stocks continue to decline and the massive production efforts led to hatchery fish constituting the lion’s share of many stocks in the basin (over 90% of coho salmon, more than 70% each of spring and summer chinook salmon, and steelhead, and 50% of the fall chinook salmon, according to NOAA (Johnson et al 2019).
Sockeye salmon originating in Idaho waters travel the furthest of all migrating salmonid species, traversing more than 900 miles with a 6500 foot elevation gain, and over/around 8 dams before spawning in the Sawtooth Valley in the headwaters of the Salmon River. In 1991, Idaho sockeye were listed under the federal Endangered Species Act as only four adult natural-origin sockeye returned to the Stanley Basin. The combined annual returns from 1991-99 were 23 fish, including the infamous “Lonesome Larry”, the single sockeye to return to Redfish Lake in 1992. Because of these alarming trends, a captive broodstock program began in the 1990’s using 11 males and five females taken into captivity from 1991 to 1998. Thankfully, the program has been able to retain about 95 percent of the species’ remaining genetic variability. Fast forward to the end of August, 2019, and a mere 15 sockeye have returned to their origin, including the first and only return from the Springfield hatchery brought online in 2013. Conservation and management of Idaho sockeye illustrates the degree of difficulty and amount of resources it can take to maintain a severely imperiled, anadromous species. Unequivocally, however, if it weren’t for hatcheries, there would be no more sockeye salmon returning to Idaho.
Bandied about in the fisheries world is the concept of the 4 H’s: Hydro, Habitat, Hatcheries, and Harvest. These are four main factors that affect freshwater migrating species. I’d like to highlight an important part of habitat that was glossed over (if mentioned at all?) in “Artifishal” – ocean conditions. Most likely, when we think about salmonids, we think about them struggling upstream to their spawning grounds. However, salmonids can spend more than half their lives, anywhere from 2 to 6+ years depending on the species, in the ocean where they feed and grow, but environmental conditions are often easier to monitor in rivers. We can observe when they begin their freshwater migrations and track water quality, flow regimes, and temperature. Obviously, this is more difficult in the ocean, especially if they head off-shore. Nevertheless, recovery of these species obviously depends on favorable oceanic conditions where they spend their time maturing, but at this point, the ocean is a big black box with regard to its measurable effect on salmonids. What we do know is that five years ago, an expanse of warm water, seven degrees Fahrenheit above average temperature (i.e. the “blob”), developed that stretched from Alaska down to California and corresponded with diminished salmon returns. And good news, everyone! The blob is back. As ocean monitoring progresses and time-series datasets become available, we may start to see direct associations between salmonid return abundance and ocean conditions. A recent study links oceanic indices associated with climate change – sea temperature, ice coverage, and phytoplankton blooms with juvenile chinook salmon growth (and by extension, survivability). The study included growth data of juvenile chinook salmon from 1974 to 2010 in two regions of the East Bering Sea (EBS) and showed that cooler temperatures and sea ice coverage meant that a lipid-rich prey item, capelin, were more abundant, which led to greater growth of salmon. Furthermore, in the southern EBS where temperatures were higher and fluctuated more and sea ice was less predictable, environmental variables were better predictors of salmon growth (or lack thereof) than in the more stable north EBS. If this trend continues, management of salmon fisheries and prediction of returns will become more challenging in the EBS if sea temperatures continue to rise and sea ice coverage continues to vary.
Some excellent points were raised in “Artifishal” about the complications around hatcheries (I saw the film a month ago so some details may be foggy.). For example, are large amounts of resources going into these programs? Yes. Is the return on investment slow to grow? Yes. But to lump open net pen aquaculture and all hatcheries together, and call for the disbandment of all hatcheries is woefully myopic. The documentary implied that hatcheries are THE factor causing the depressed returns without taking into account changing oceanic conditions. So let’s suppose we dismantle all hatchery programs and wild stocks continue to decline. Now we have no biological reserves. If we had taken this tack in the 1990’s sockeye salmon in Idaho would be gone. Therefore, I find the final message in the film to be overly reactionary and careless. There are improvements to be made but to jump to the conclusion that all hatcheries are detrimental to all wild fisheries is unreasonable and alienates a cadre of managers that have the same goal as activists: restoration of salmonid runs to sustainable, healthy numbers.
Evans, M.L., Hard, J.J., Black, A.N., Sard, N.M., O’Malley, K.G., 2019. A quantitative genetic analysis of life-history traits and lifetime reproductive success in reintroduced Chinook salmon. Conserv Genet 20, 781–799. https://doi.org/10.1007/s10592-019-01174-4
Janowitz‐Koch, I., Rabe, C., Kinzer, R., Nelson, D., Hess, M.A., Narum, S.R., 2019. Long‐term evaluation of fitness and demographic effects of a Chinook Salmon supplementation program. Evolutionary Applications 12, 456–469. https://doi.org/10.1111/eva.12725
Johnson, B.M., Johnson, M.S., Thorgaard, G.H., 2019. Salmon Genetics and Management in the Columbia River Basin. nwsc 92, 346–363. https://doi.org/10.3955/046.092.0505