By Andrew L. Rypel and Peter B. Moyle
The photo is a common one (Fig 1). Large numbers of fish are being released into a river, stream or estuary – products of a fish hatchery. A politician or government leader looks on, or even participates in the release, says a few words, and then grabs a photo opportunity for the press or social media. It *looks* good, like we are doing our best to save and improve fisheries. But, does it actually work?
On the surface, fish hatcheries strike many as an example of a management approach that is effective. If we don’t have enough fish, why not just grow more fish in a hatchery and release them into the wild to boost populations? Yet on closer inspection, a variety of problems arise from reliance on hatcheries to support fisheries or to ‘save’ endangered species. Often fish populations continue to decline even if supplemented with large numbers of hatchery fish.
Thus it is worth periodically evaluating the assumptions behind hatcheries – to ensure that the public’s investment is sound, to make sure the hatcheries are doing more good than harm, and to consider ways to make hatcheries function better for fish conservation. This essay reviews the evidence and discusses the effectiveness of fish hatcheries generally, especially given current ecological and environmental trends.
We are in the midst of a freshwater biodiversity crisis
Nature continues to unambiguously signal that we are rapidly destroying freshwater ecosystems and biodiversity. This applies globally, and in California. 72% of North American freshwater mussels are endangered, threatened or of special concern (Williams et al. 1993), and mussels in California are struggling (Rypel 2020; Lawrence et al. 2023). Globally, about 30% of all freshwater fish species evaluated by the IUCN are threatened with extinction, a conservative estimate (Moyle and Leidy 2023). 83% of California fishes face extinction if present trends continue (Moyle et al. 2011). These declines have all occurred over a period during which hatcheries have proliferated. In a recent high-profile review, Terui et al. (2023) concludes “current overreliance on intentional release [of hatchery fishes] may accelerate global biodiversity loss with undesired consequences for the provisioning of ecosystem services.” In other words, long-term release of hatchery fish into the wild often has an opposite impact of what we intend.
While use of hatcheries as a management tool began in California in the 1870s (Halverson 2010), hatchery construction and use exploded during the 1920s to 1960s, generally coincident with building large dams. Fisheries managers at the time were convinced hatcheries would make up for lost natural production of salmon and steelhead caused by dams and diversions. Today, most Central Valley rivers remain blocked by large dams and no longer support salmon and steelhead populations maintained by natural reproduction (Rypel et al. 2020). But almost all have salmon populations sustained, if declining, by large production hatcheries (Katz et al. 2013). And this is not just a California story. Despite increased investments in hatcheries and fish production across the Pacific northwest, widespread salmon declines continue (Black 1995; Welch et al. 2021).
Learning from Indigenous systems of management
There is growing recognition that knowledge and stewardship actions used by Indigenous communities can support successful and equitable conservation (Polfus et al. 2016; Atlas et al. 2020). As an example, Schuster et al. 2019 showed that lands managed by Indigenous communities have levels of vertebrate diversity similar to those in parks and other types of protected areas. Across the Pacific Rim, Indigenous communities have sustainably harvested salmon and other fishes for thousands of years. Compiled narratives from communities show that many Indigenous management systems are grounded in cultural and spiritual beliefs, communal laws, and traditional management practices (Harris 2001; Ritchie and Angelbeck 2020). In contrast, production of hatchery fish across the globe is, by-and-large, a product of fisheries management systems devised by industrialized nations. Hatchery fish are sometimes released into the environment with little regard for their effects on local ecosystems or on wild fish that already live in the recipient ecosystems. There is even strong evidence that hatchery supplementation during periods of low ocean productivity, can exceed the carrying capacity of marine habitats thereby generating high ocean mortality (Levin et al. 2001). This can result in fewer salmon contributing to fisheries rather than more! Therefore, because there is movement to reaffirm Indigenous control over fisheries, it is worth also evaluating how much modern hatchery systems align with the needs and knowledge of Indigenous communities. And while inclusion of Indigenous communities is generally increasing, the degree to which these perspectives are actually integrated into hatchery decision making is unclear, and at best, context dependent (Palaka 2019). As we discuss in the next sections, holistic approaches based on habitat restoration and management are generally preferred by Indigenous peoples.
Ecological reality versus human desires
Most natural populations, without intervention, fluctuate through time, but generally maintain stable abundances over the long-term. Under this view, Indigenous peoples were integrated into local ecosystems, and presumably had fairly stable populations. Yet modern desires (and demands) by Western cultures follow a distinctly different demand curve shape of, not just stable, but often increasing supply. Sass et. al. 2017 captures this important dynamic in their conceptual figure (Fig. 3). And as populations decline, gaps between nature and the new reality only widen, while human demands just continue to increase, often well above any historical baseline of what is reasonable.
With our culture’s faith that technology can solve all problems, it is unsurprising that hatcheries have been deployed as the method of choice to maintain and restore fisheries. Unfortunately, science just doesn’t support this solution in the vast majority of cases (Moran et al. 1991; Yosef et al. 1996; Araki 2010; Quiñones et al. 2014). Often ineffectiveness traces back to habitat issues. Thus if more fish are stocked onto the same degraded habitat, there is nothing magical that is going to allow fish – hatchery and non-hatchery – to survive and grow better than the original native population. Quite the contrary. But many still believe in a magic potential of supplementation. A large experiment is currently playing out with the planting of hatchery-reared delta smelt (Hypomesus transpacificus) in the San Francisco Estuary, to supplement wild populations; wild delta smelt may or may not continue to exist. Yet without better smelt habitat in the estuary, it is doubtful any supplementation will result in reproducing populations at scale even close to their original numbers. However, supplementation in concert with habitat management may work better – more on this later.
Domestication and inbreeding has negative effects
Wild fish populations are the product of natural selection (fitness). Hatcheries interrupt the natural evolutionary process and instead inject human selection into the equation. When breeding occurs in a hatchery to produce fish with desired traits, the fish used are selected by humans, not by other fish and the natural environment. This leads to an important question as to whether hatchery-raised fish have been domesticated and possess traits that reduce their ability to survive in the wild, as well as, reduce genetic diversity overall (i.e. are “bottlenecked”). The best available science broadly supports the notion that hatcheries commonly do result in domestication (Araki et al. 2008; Hayes et al. 2012; Christie et al. 2016). Domesticated fish released back into the wild, especially if stocked on top of wild fish populations, have the potential to breed with wild fish, which might in turn reduce fitness of wild stocks. These same fish can spread diseases and also compete with wild individuals for food and space. Further, because hatchery-reared fish are often grown to larger sizes than their wild counterparts of the same age, the strength of this competitive effect can be strong. Many state fish management agencies strictly prohibit stocking of hatchery fish on top of naturally reproducing populations.
Hatcheries are expensive
The costs of running large hatchery operations are sizable. Consider the building, maintenance, staff, feed, truck costs, gas costs, plumbing costs, upgrades etc. needed to run large hatchery operations. Given such large infrastructure investments, the desire is often to use that investment maximally, and stay the course, even if the idea isn’t a good one anymore. This is a general idea sometimes referred to as the “sunk-cost” fallacy. Therefore it seems reasonable for the public to occasionally ask whether large public investments are genuinely delivering on the promise. Alternatively, might practices might be tweaked to improve efficacy.
Should we abandon hatcheries?
We don’t think so. In his 2013 book, Malcolm Gladwell explored the concept of ineffectiveness and underdogs, primarily through a series of case studies. Gladwell points out that sometimes strategies and tactics we perceive as being effective are actually not. Furthermore, things sometimes perceived as disadvantages and weaknesses can be converted into strengths and successful plans that have outsized impacts.
There are important success stories out there to consider. We have at times reported on the interesting story of Putah Creek salmon. Following stream rehabilitation and restoration of flows, Chinook salmon began coming back to Putah Creek (Willmes et al. 2020). Research at UC Davis has demonstrated these salmon originated primarily from hatchery strays, many of which were trucked or barged as juveniles from a hatchery to the San Francisco Estuary during drought (Willmes et al. 2021). This important case-study seems to demonstrate that hatcheries can provide fish capable of recolonizing degraded California streams, provided these habitats are restored to conditions capable of supporting salmon in the first place. This process typically involves removal of fish passage barriers, and restoration of natural flow processes that promote native assemblages, attract salmon in the fall, and successfully push out juvenile salmon in the spring. The return of Putah Creek salmon can be considered a real success, and hatcheries were, perhaps unintentionally, a major part of the success (Willmes et al. 2020). We can learn from this. Evidence is mounting that some of the current population of Putah Creek salmon are of natural origin, but the founding new population was originally composed of lots of straying hatchery fish. The formula for success was: 1) That the habitat was fixed; 2) hatchery fish colonized and successfully spawned in the new habitat; and 3) managers, communities, and scientists collaborated over many years and difficult challenges to improve the habitat for salmon further (Rabidoux et al. 2022; Rypel et al. 2022).
Well-targeted hatchery campaigns can also be effective at bringing back species from the brink. Some of the hatchery efforts to recover Lahontan Cutthroat Trout (Oncorhynchus clarkii henshawi) and Cui-ui (Chasmistes cujus) to Pyramid Lake strike us as wonderful collaborations that have yielded real results for ecosystems and people (Al-Chokhachy et al. 2020; see also video below). And the herculean efforts to bring spring-run Chinook salmon back to the San Joaquin have been important, following a similar formula as that observed for Putah Creek. In this case though, hatchery releases were intentional and conducted in lockstep with major habitat and flow rehabilitation – leveraging high-quality science and community partnerships (Rypel et al. 2020). These successes don’t occur overnight or accidentally, but are the direct product of years of coordinated hard work, collaboration, and ongoing experimentation, science, and refinement.
Hatcheries can also support struggling communities. Harvesting and eating fish is actually another great reason to conserve them (Moyle 2020). The California salmon fishing season has been canceled this year because of low salmon numbers. The cancellation will have major economic impacts on the fishing and seafood industries in California. Hatcheries can provide some support to the tribal, recreational, commercial fishing communities. Again however, domesticated and wild stocks should be segregated to the fullest extent possible. Managers may ultimately need to explore alternative supplementation approaches, such as terminal fisheries for some harvested stocks (Schnute and Sibert 1983), to enable fuller segregation, and to shift conservation focus back towards the habitat needs of the remaining wild fish. It would also be helpful to understand the impacts of harvest on struggling populations; tools that might be helpful include a 100% mark of hatchery fish and direct surveys of which stocks are actually being harvested, and at what rates.
Finally, sometimes the hatchery is the only place left for a species to go. This is the predicament in which delta smelt find themselves. Their essential habitat in the wild is now so altered that it lacks the attributes needed to support large wild populations. The hatchery has become the equivalent of a hospital bed for the species because it cannot sustain itself in the wild any longer. This is clearly an appropriate role for hatcheries, and sadly, one that will only grow in the coming years as more species continue to slide towards extinction. The question becomes then, how many hatchery-hospitals are we willing to support, indefinitely? Isn’t a more sustainable solution to protect and restore habitat, so fish now in hatcheries can develop self-sustaining populations?
Putting the pieces together
Wildlife ecologists long ago figured out that habitat work is the primary and best path to regaining wildlife populations. In wildlife management, there is some reintroduction of species into their former native ranges, limited stocking for put and take hunting, and captive breeding (often in collaboration with zoos). But stocking is minimally used overall, whereas in fisheries, it is often the dominant mode of management. According to Sass et al. 2017, fisheries science in relation to habitat management is at a similar point that wildlife ecologists were in the 1970s. Essentially, we are just beginning to awaken to the importance of large-scale habitat conservation management for saving fishes and fisheries.
A recent study from Europe (Radinger et al. 2023) provides the strongest experimental test to date of aquatic habitat rehabilitation benefits. The researchers conducted whole ecosystem experiments across 20 independent lakes. In the lakes, they manipulated/restored different aquatic habitats while also manipulating stocking. They then tracked fish population response in each of the lakes over a period of 6 years. In the end, they found species stocking efforts failed, but that the habitat rehabilitations worked in enhancing fish abundance, especially when multiple habitats were restored in combination with one another.
Why hasn’t habitat restoration been prioritized better? We occasionally hear that the expense of habitat rehabilitation is just too great versus the ease of stocking projects. Yet while habitat rehabilitation may not provide an easy solution, it is more likely to sustain fisheries in the long-term. Indeed, blending hatchery and habitat management practices strikes us as an important frontier for improving management of our fragile fish biodiversity. Producing more and more fish with little regard for their habitat will continue to fail. And while it might look good for the politicians, without the habitat piece, present downward trends will definitely continue.
How might hatcheries be embedded into a broader habitat conservation strategy for California? Having a strategy is of course a solid first step (Rypel et al. 2021). Across California however, there are large and small aquatic rehabilitation projects that matter. The Klamath River Dam removals is the largest dam removal project in US history. Hatcheries could play an important role in recovering Chinook salmon and native suckers in the Klamath River, but it’s unclear currently exactly what that might look like. And after a long absence on the landscape, Lake Tulare has come back this year (Moyle 2023). There is widespread confusion about what to do with Lake Tulare now, but partial recovery of the lake may be possible, if we want it. Could hatcheries play a role in the resurrection of an iconic and long-forgotten ecosystem? Finally, there are other important and emerging statewide initiatives. This includes the 30×30 initiative, a long-overdue focus on reestablishing beavers, floodplain management (Torres et al. 2022, Rypel et al. 2022, Mount et al. 2023), environmental flows (Grantham et al. 2020), and so many others. There are also many examples (not to be named) of dubious “restorations” and/or “habitat improvements”.
Can we get fishes on floodplains more often and for longer durations to improve their survival? Can we better restore habitats in the Delta such that they can better receive hatchery-reared delta smelt? Can we manage river flows in real time to facilitate improved outmigration of juvenile salmon? Smart people are already working on these ideas, which is excellent, and it is the type of thinking we will need to save our fishes. We also need to face the dragon, and begin to address the larger socioeconomic issues that are driving our fish populations to extinction in the first place. Improving hatcheries will be important to everyone, but perhaps especially to those politicians who want that photo to mean something genuinely great is being accomplished.
“…before timber harvest robbed rivers of their protective forests; before fishermen’s nets swept through the rivers and bays; before glaciers gouged out Puget Sound… before all this, there were the salmon.”
~J. Lichatowich (1999)
Andrew L. Rypel is a professor of Wildlife, Fish & Conservation Biology and Co-Director of the Center for Watershed Sciences at the University of California, Davis.Peter B. Moyle is a Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences.
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