SALTWATER HATCHERIES: DUBIOUS BENEFITS, UNRECOGNIZED RISKS

 

Saltwater fishermen have traditionally been at the mercy of the ocean, and of their own behavior.

Unlike their freshwater counterparts, who often fish in man-made ecosystems, for non-native fish that, in many cases, were spawned not in nature, but in shallow pans on a hatchery rack, saltwater fishermen have long been dependent on native species, on the swings of abundance caused by the success or failure of previous spawns, ocean conditions, and on effective stewardship of marine fish stocks.

But as fishing, climate change, and other stressors impact fish stocks, some people have started to call for saltwater fishery managers to emulate the folks managing inland fisheries, and begin stocking fish to increase abundance without resorting to more restrictive regulations.

That has long been the case in Texas, a state that regularly dumps artificially propagated red drum, spotted seatrout, and southern flounder into its coastal waters, effectively subsidizing recreational overfishing.  Instead of adopting regulations restrictive enough to maintain a sustainable harvest of naturally-spawned fish, Texas freely admits that it employs hatcheries

“to ensure that harvest levels are sustained,”

Instead of adopting management measures better suited to the productivity of local fish stocks, the state boasts that it operates

“one of the most visible marine stock enhancement programs in the world.”

While there’s little doubt that the Texas hatchery program has allowed anglers to ice many more redfish and seatrout than they would have been able to remove from natural populations, there is little clear indication that stocking did the red drum much good.  A 2000 paper published in the Transactions of the American Fisheries Society, written by a scientist with the Texas Department of Fish and Wildlife, observed,

“Previous research that compared red drum length frequencies in stocked versus unstocked estuaries and analyzed the capture rates of fish with chemically marked otoliths indicates that stocked red drum can contribute to wild populations at the local scale, but the results are not definitive.  The data necessary for an accurate estimate of the proportion of hatchery-reared fish remaining in the estuary after several years and their contribution to the red drum population is difficult to obtain and not available currently…Correlations between annual stocking rates and age-0 or age-1 [catch per unit effort] were not significant across estuaries or years, suggesting no population-level effects of consistent annual increases in stocking or interestuary variations in stocking rates.  However, because all estuaries received some hatchery-reared fish during the period of this study, abundance levels of age-0 and age-1 fish in the absence of stocking cannot be inferred.  Therefore, although trends in resource monitoring data did not demonstrate clear stocking effects, release of hatchery-reared fish may still have enhanced red drum populations.  [references omitted]”

 According to an article published in Sport Fishing magazine, DNA testing performed by the State of Texas has found that between 1 and 17 percent of the red drum sampled each year were hatchery fish.  In most years, the proportion of hatchery fish exceeds 4%, which is deemed to be the point where the economic value of the drum caught by anglers breaks even with the expense of artificially rearing the fish, which makes the hatchery program an economic, if not a biological, success.

The same thing can’t be said for the white seabass hatchery established by the State of California.  

Over the past 35 years, California has spent about $40 million to manufacture sea bass, which are then released into the Pacific.  However, probably because the fish suffer very high mortality rates after being released, the stocked fish have had little impact on either the white seabass population or on the fishery.  Yet, while the hatchery has released over 2 million juvenile white sea bass into the wild, a panel of scientists has determined that less than 1% of the fish caught off southern California are of hatchery origin.  The steady increase in biomass is more likely due to a 1990 law that outlawed the use of gillnets in California’s state waters.

Yet, despite the questionable biological benefits of stocking, state management agencies are continuing to move in that direction, in order to provide more fish, and less restrictive regulations, for their anglers.

Thus, beginning in 2014 Mississippi began to release hatchery-raised red snapper into the Gulf of Mexico, as part of a research project being conducted with scientists at a state university that seeks to find ways to increase the availability of snapper to fishermen.  Other Gulf states also maintain or are contemplating hatcheries that will artificially rear popular marine fish species.

As noted by Max Westendorf, the director of Alabama’s Gulf Shores hatchery, the primary purpose of marine hatcheries is to keep fishermen happy, not to maintain fish stocks, which can be done by merely adopting appropriate regulations.

“If you don’t have the hatchery, and let’s say you just do fishing regulations and commercial regulations and fisheries management, you end up kind of just making people mad when you start telling them you can’t [fish].”

So if the primary purpose of marine fish hatcheries is merely to make fishermen happy, and buffer them from the worst impacts of their own harvest, the most important question to ask is whether such hatcheries could do any harm to wild fish stocks.  Such harm could, in theory, come in a variety of forms.  Hatchery fish might cause genetic damage to wild stocks, or they might increase the competition for food, spawning areas, etc.

Are those real threats?

The answer seems to depend on the species involved, and the type of threat being considered.  But recent information coming out of Alaska suggests that introducing too many artificially reared fish into the ocean could impact not only a single species, but an entire ecosystem.

Every year, hatcheries along the northern Pacific Rim—from Japan to Alaska—produce and release about 1.3 billion pink salmon fry; enough survive that about 82 million adult fish return to coastal rivers every other year.  While pinks are the most abundant salmon species, and the hatchery-spawned adults only account for about 15% of returning pink salmon, those 82 million fish are roughly equal to the entire wild sockeye salmon population, and outnumber the wild chum salmon, chinooks, and cohos.

All of those hatchery fish have to feed heavily in order to return to coastal rivers in spawning condition; they can increase their weight by 500% in only four months.  They compete with other salmon species for the available forage, and with species such as sockeye also abundant in Alaskan waters, there may not be enough forage to go around.

It appears that the average size of salmon is falling as a result.  An article in Hakai magazine notes that the size of chinook salmon has dropped by 8% since 1990, while the size of other species has fallen by lesser amounts.

Studies dating back to the 1970s suggest that there is an inverse relationship between the abundance of pink and chum salmon; when the pinks, which peak in abundance every other year, exhibit high numbers, the numbers of chum salmon trend low.  Growth rates of sockeye salmon also seem to wane when pink salmon are abundant.  In a finding that might explain such variations, researchers discovered that when pink salmon were abundant, there was a sharp drop in the abundance of copepods and other large zooplankton, suggesting that the pinks were having a substantial impact on the North Pacific food web.

Such impacts have been linked to declines in the abundance of herring and mackerel, and also on the nesting and survival of seabirds that are dependent on fish that, in turn, need abundant zooplankton to thrive.  It even appears that the abundant pink salmon could be causing an increase in killer whale mortality, and their impact on the food web reduces the numbers of chinook salmon, on which the whales feed.

Hatchery-produced pink salmon are so much a part of Alaska’s commercial salmon fishery—some operations earn a third of their revenues from the hatchery fish—that it is highly unlikely that such production will stop at any time soon, particularly given that scientists are split on the question of whether the hatchery fish are doing real harm.  But in other places, where hatchery fish have not yet been woven into the fabric of local fisheries, it is time to ask whether it is wise to dump thousands, if not millions, of fish into the water each year, merely to give fishermen something to catch.

While hatcheries might provide a logical and valuable response to local catastrophes, such as the impaired river flows that threatensalmon runs in California, or perhaps even the damage that the red tide haswreaked on Florida’s coastal fisheries, they should always be seen as a temporary response, an interim measure intended to support wild populations until natural reproduction can return to more typical levels.

In areas with healthy populations of fish, where recruitment is not an issue, flooding the ocean with man-made fish can lead to problems as easily as to solutions, and should be avoided in favor of regulations that constrain landings to levels that are sustainable in the long term. 

Hatcheries are seductive, as they seem to offer abundant fish without the discipline imposed by stringent regulation.  Yet, in the history of North American fishery management, it is difficult to find an instance, whether in fresh water or salt, where extended periods of stocking have left a native population in better condition than it was in when the stocking began.

That, in itself, should condemn the practice.