Japan’s fading chum salmon production in the new millenium/NPAFC graphic

Decades into what was once the world’s most productive ocean ranching operation, Japanese researchers have concluded that nation’s hatcheries managed to breed some of the resilience out of their salmon and undermine the homing instincts of the fish.

As a result, the scientists are predicting continuing declines in Japanese salmon production in a warming North Pacific Ocean that has proven beneficial to wild Russian and Alaska salmon stocks to the north of Japan.

Hatchery-driven changes at the genetic level have resulted in the opposite for Japanese chum salmon, report researchers from the Tokyo Univesity of Marine Science and Technology and Tokyo University.

Japan still runs the biggest hatchery chum program in the world, but its overall hatchery production has been surpassed by that of an Alaska-led U.S. The U.S. now dumps about 2 billion, young, hatchery salmon into the ocean every year.

Alaska annually contributes 80 to 90 percent of those and annually sees returns of 50 million or more adults. State-funded hatcheries in Prince William Sound later turned over to a commercial fishermen’s cooperative that now runs them as private, non-profit businesses have been a godsend for the state’s Southcentral region.

They produced a harvest of about 38 million salmon there last year, according to Alaska Department of Fish and Game reports. About 32 million of those fish were small, low-value pink salmon, but 4.8 million were larger, higher-value chums.

Statewide, Alaska’s 30 hatcheries produced about 13 million chums in 2019, or about 75 percent the number of chums now produced by the Japanese ocean-ranching program that served as something of a model for the state in the 1970s.

Troubling data

While Alaska hatchery salmon production has been going up, Japan hatchery production has been going down.

In Japan, hatchery-driven adaptaions appear to be causing genetic replacement in thermally adapted genes resulting “in lower metabolic efficiencies in skeletal muscle and mitochondria at higher temperatures,” researchers write in a paper now posted at BioRxiv. “Field experiments have demonstrated that Japanese hatchery fish have lower athletic ability and our observations of YouTube videos consistently indicated the slow movement of Japanese chum salmon.

“Such physiological changes may reduce survival rates of hatchery-born juveniles on Japanese coasts in the face of warming sea surface temperatures (SST) and also in the Sea of Okhotsk, where competition for food is expected to be high because of substantially increased Russian chum salmon abundance.”

North Pacific-wide, chums are at a historic peak in numbers, but Japanese chum catches have fallen from 81 million of the fish in 1996 to only 17 million last year. This despite the operation of the largest chum-salmon hatchery operation in the Pacific.

“At present, 262 salmon hatcheries operate in Japan,” paper authors Shuichi Kitada and Hirohisa Kishino wrote. “Releases of chum salmon juveniles from Japan have increased remarkably since the 1970s to approximately 1.5 billion in 2018.”

Japan largely eliminated its wild runs of salmon in favor of producing fish more effeciently with hatcheries. The transition met with early success.

“Supported by natural shifts in marine productivity, the number of chum salmon returning to Japan sharply increased after the 1970s. Nevertheless, the mean body weight of chum salmon returning to Japan during this time significantly decreased,” the researchers write.

The decrease in size – something which is also being seen among salmon almost everywhere in the North Pacific – is largely attributed to intra- and inter-species competition for food on the ocean pasture though that connection has not been definitively proven.

Food competition would be a likely reason for the decline in the survival of Japanese hatchery fish,too, and such a decline would only be accelerated by hatcheries breeding increasingly less resilient young fish.

Facebook of science

Kitada and Kishino did a deepdive into the genetics of the chums both present and past to buttress their hypothesis to explain the crash in Japanese chum production, but their highly technical paper has not been peer reviewed.

Scientists who have historially supported hatcheries as a more efficient means of producing “wild” fish will no doubt find data points with which to take issue. The Rxiv sites have become the Facebook of science in terms of inviting everyone into scientific ponderings.

“bioRxiv (pronounced bio-archive) is a free online archive and distribution service for unpublished preprints in the life sciences,” the webiste notes. “It is operated by Cold Spring Harbor Laboratory, a not-for-profit research and educational institution. By posting preprints on bioRxiv, authors are able to make their findings immediately available to the scientific community and receive feedback on draft manuscripts before they are submitted to journals.”

The Rxiv services for life sciences and medicine (COVID-19 studies are exploding on MedRxiv) have been hotly debated by professionals.

”…The problem is that such servers blur the line between peer-reviewed articles and fake news,” Bernhard Hommel from Leiden University in the Netherlands observed at Research Gate, a search site for science.

“Many authors and readers treat pre-publications just like peer-reviewed papers accepted by a journal, and so we read twitter messages about “evidence for xyz” with a link to unreviewed papers with sometimes questionable methodology and conclusions, and laypeople (and I‘m afraid some researchers as well) take that as scientific evidence already. That has the potential to undermine the credibility of our science.”

Despite this potential problem, many respected scientists are now posting on the Rxiv sites that appear to be taking over the world of science. Kitada is an established researcher who has been warning about genetic problems in Japanese hatchery salmon for years.

A 2014 article he wrote suggesting “new research is needed to minimize the genetic risks associated with hatchery programs” was “selected by the Editorial Board of the Japanese Society of Fisheries Science for the purpose of distributing thoroughly useful research works in aquatic biological sciences,” the organization wrote on its website. 

Kitada’s latest work in cooperation with Kishino adds meat to the bone of his earlier worry. The two scientists now point to specific gene losses they think are weakening Japanese chum stocks.

“Almost all chum salmon returning to Japan are hatchery-released fish or possibly wild-born hatchery descendants that have distinct genetic characteristics as demonstrated in this study,” the conclude. “Japanese chum salmon populations may thus continue to decline, with variations under current hatchery practices, as reduction in survival rates of hatchery-reared fish is cohort-specific and constant over time within a cohort.

“Our results, which were obtained from the world’s largest marine stock enhancement program, should inform our understanding of long-term impacts of animal artificial propagation, including that of salmonids and marine and freshwater species, for fisheries and conservation objectives.”

Thes state of Alaska is at the moment deep into its own study of hatchery genetics. Hatcheries have long been considered purely a “good” thing. No significant studies of the environmental consequences of dumping hundreds of millions of hungry, young fish into ocean bays and estuaries have ever been required of them.

When the U.S. Forest Service completed an evironmental impact statement for the expanion of the Main Bay hatchery in the Chugach National Forest in 1993 it wholly ignored the issue of inter-species or intra-species interactions in the marine environment and focued on the “need” to expand the hatchery to ensure the “equitable distribution of ahtchery salmon among varous user groups.

“As such, the major goals of the expansion are to increase sustained production of sockeye salmon and to increase revenue to the gillnet fisheries in Prince William Sound. The Main Bay Hatchery is key in this plan because equity cannot be obtained for the gillnet fisheries under the required allocation policy until the expansion is complete.” 

The work of Kitada and Kishino would appear to raise some possible questions about the sustainability of that equity over the long term.