On the morning of July 11, 2023, marine wildlife veterinarian Dr. Joe Gaydos stood in front of a beautiful, six-foot-long fish that had washed up on Crescent Beach, Orcas Island. Its body was torpedo-shaped, and its skin was gun-metal gray with an iridescent sheen. Gawkers thought it looked like a tuna of some sort. In fact, someone had already carved a huge fillet out of it.

But it wasn’t in the book Gaydos brought with him, “A Field Guide to Fishes of the Salish Sea,” a newly published guide to the inland sea around Puget Sound, the San Juan Islands, and the waters off Vancouver, British Columbia. “When I saw that it was not in the book, I knew that it was something big,” Gaydos said in a podcast  three months later.

The fish, later identified as a Pacific bluefin tuna, had never been documented in the Salish Sea until that morning. As an oceanic pelagic fish, meaning a migratory fish of the open ocean, bluefin tuna has an impressive range that spans the sea around Japan to the waters off California and Mexico. It’s just not the kind of fish that would seek narrow, inland waters like the Salish Sea.

Gaydos works as the science director for the SeaDoc Society, a research nonprofit that studies and works to conserve marine wildlife and their ecosystems in the Salish Sea. He remembers thinking that morning, “Ocean temperatures are increasing; species are shifting; plants are migrating north;…birds are migrating north. We know that we are at the precipice of change…But I’m a scientist. I can’t say from one fish, oh, this is climate change! It’s just one fish. It could have gotten lost.”

Yet, thousands of miles southeast of the Salish Sea, across the Pacific Ocean, fisheries scientists, large and small fishing companies, and nonprofits in Hawaiʻi and other Pacific Islands are exploring and preparing for just that scenario. With climate change, some commercially important species of oceanic pelagic fish will gradually move from the western and central Pacific Ocean to the eastern part, closer to North American coastlines. Would that wayward bluefin tuna turn out to be a bizarre anecdote? Or would it signal the beginning of a trend of migration shifts that scientists and scientific modeling see on the horizon?

A Sea Change for the Central and Western Pacific
A National Science Foundation funded study reported in 2022 that climate change’s effect on the oceans is “complex, and difficult to predict.” Large species and commercially important fish will shift out of their historical ranges as temperatures increase. “While the species we fish today will be there tomorrow, they will not be there in the same abundance,” said study co-author Dr. Malin Pinsky of Rutgers University.

An earlier study by French and Australian scientists painted a detailed picture of what will likely happen to four dominant species in the Pacific Ocean’s fisheries. The 2018 study predicted that skipjack and yellowfin tuna will gradually shift eastward over 50 years. Bigeye tuna will also move eastward, though not as much as skipjack and yellowfin. Projections for Pacific albacore varied widely. The study also predicted an increase of tuna in the high seas, implying that larger catches will happen in international waters rather than around Pacific Islands.

The potential upheaval is huge and portends changes for major fisheries in the Pacific. “Skipjack tuna is what you find in canned tuna,” said Dr. Mark Fitchett, pelagic fisheries ecosystem scientist at the Western Pacific Regional Fishery Management Council (WP Council). “The price per pound is lower. But because there’s so much being caught and it’s so prolific, skipjack tuna is the number one economic driver.”

The council is one of eight regional fishery management councils in the U.S. mandated to prevent overfishing, reduce bycatch, and protect fish stocks and their marine habitat.

“Sixty percent of the global tuna supply is caught in the western and central Pacific,” Fitchett added. “Half of that catch is caught in the waters of twenty-two Pacific Island countries and territories. That puts things in perspective.”

The change could adversely affect the tuna-dependent economies of ten small island states. Many Pacific Islands grant fishing rights to foreign fishing fleets in exchange for access fees. In the case of Tokelau, Kiribati, Tuvalu, the Federated States of Micronesia, the Republic of the Marshall Islands (RMI), Nauru, Kūki ʻĀirani (the Cook Islands), the Solomon Islands, Palau, and Papua New Guinea, the income from these access fees make up an average of 37 percent of their government revenues.

By 2050, the eastward shift of skipjack and yellowfin tuna would likely decrease the species in Papua New Guinea but likely increase them in French Polynesia. By the second half of the century, the decrease will extend to most other small island states west of 170 degrees longitude. However, Vanuatu, Samoa, American Samoa, and New Caledonia will see an increase.

Pacific bluefin tuna, which has a more northern migratory route compared to skipjack, yellowfin, bigeye, and albacore, is projected to slightly increase in abundance in the Eastern Pacific Ocean, according to a study by Spanish researchers. In-demand and pricey in sushi restaurants, the Pacific bluefin tuna is listed by the International Union for Conservation of Nature as “near-threatened.” But international restrictions reducing the catch of young bluefin and limiting the catch of larger adults helped the species rebound more recently. Although there haven’t been recent studies predicting the species’ migration due to climate change, there have been anecdotal sightings of bluefin in colder waters such as east Greenland, in addition to the sighting in the Salish Sea.

A Fresh Fish Fishery Has Its Limits
How would climate change affect fisheries in Hawaiʻi and U.S.-Affiliated Pacific Islands (USAPI)? A 2018 study showed that as climate change continues to unfold, a decline in catch may be inevitable for bigeye tuna in the Hawai‘i deep-set longline fishery. It projects a 7 percent reduction in bigeye biomass by 2050 and a 20 percent reduction by 2100. Increasing yields would not be possible.

“Hawaiʻi’s fishery for the most part is a region-specific fishery,” Fitchett said. “The vessels are capped at a certain size, and their range is limited. They can’t move around like distant water fleets from China, Japan, and South Korea where they have freezers on board. It’s a fresh fish fishery.”

It’s a different story for swordfish. If fishers refrain from increasing their catch volume, swordfish abundance could remain unchanged into 2100, even with the worst climate change scenario. However, while there may be the same number of swordfish, they will be smaller.

The shift in fish distributions caused by climate change will definitely drive where Hawaiʻi’s longline fleet can fish. But it’s also going to drive how far the fleet has to go to fish. That has an economic cost.

Choose Pelagics in Palau?
These island countries and states need to figure out how to stay resilient as these projected changes happen, but the challenges may be different for each country. For example, the departure of tuna for the east won’t impact the economy of Palau as much as other small island states. Fishing access fees only contribute 9.4 percent of their government revenue, compared to 47.6 percent in neighboring Federated States of Micronesia.

However, it complicates the small nation’s ambitious measures to improve food security and its resilience to climate change. Palau established a large marine sanctuary in 2015 and closed 80 percent of its economic exclusion zone to commercial fishing and oil drilling. The country did this to protect its waters from overfishing and unsustainable fishing practices, like bycatch. They also wanted to strengthen their domestic tuna fishery to feed their own citizens.

Along with these measures, the government chose a nature-based strategy to restore their coral reefs. “We recognize that the health of the reefs depend on a healthy herbivorous fish population,” said Steven Victor, who leads the Palau Ministry of Agriculture, Fisheries, and Environment. Herbivores, like parrotfish, nibble and clean algae that could deprive coral of light and oxygen. They also encourage coral growth by nibbling on dead coral.

“However, Palauans like to eat these herbivorous fish,” Victor said. “So there has been an effort over the last five years to try and encourage Palauans to eat more pelagic fish.” Victor has seen a shift towards pelagic fish like wahoo, Spanish mackerel, and tuna, but adds that the change has been slow because these fish are expensive.

If and when large fish like tuna become less abundant in the waters around Palau, what then? Victor is firm in saying the best solution is still to address further climate change by reducing fossil fuel emissions.

“We’re taking a global approach by continuing to call for high ambition from big emitters to reduce fossil fuel emissions, as well as to phase out fossil fuels,” Victor said.  “That’s the long-term solution that we need to get climate impact, fisheries, and people at a level where we can manage challenges. We know it will be costly, but at least it can be managed.”

Big Fish Eat Little Fish Who Eat Plants
What is the science that underpins these projected changes? Although the Pacific Ocean is vast and its processes dynamic and complex, the global models predicting these changes are based on the simple principle that fish follow their food.

Migratory pelagic fish like tuna and swordfish prey on micronekton, which are small, swimming organisms like crustaceans, cephalopods, and tiny fish, typically less than half an inch to about four inches in size. Micronekton eat zooplankton–microscopic animals, like pelagic worms, krill, and sea snails. Fish larvae and most zooplankton eat microscopic ocean plants called phytoplankton.

Scientists study and map concentrations of phytoplankton in oceans because these provide clues to where larger fish, like tuna, are spawning and feeding. They examine ocean surface chlorophyll concentration, which can be detected by remote sensing satellites, as a proxy for phytoplankton presence in the oceans.

“Phytoplankton production is really an essential energy source in the oceans,” said Dr. Jamison Gove, a research oceanographer for the Pacific Islands Fisheries Science Center, in a presentation of Hawaiʻi’s 2022 ecosystem status report. “It dictates marine ecosystem trophic structure and drives global fisheries.”

Climate change is bringing increasing temperatures in the ocean. Warmer surface waters hinder the mixing of water layers, reducing the transfer of oxygen from the atmosphere to the ocean’s deeper layers, and the cycling of nutrients from the deeper layers to the surface.

Like their flora counterparts on land, phytoplankton need nutrients like nitrates, sulfur, and phosphates. One way these elements accumulate in the oceans is by rivers delivering sediments from weathered and eroded rocks on land. Some nutrients also come from decaying plant and animal matter sinking down the water column and settling on the seafloor. So, areas of the ocean with the highest concentrations of dissolved nutrients tend to be close to land or deep in the ocean. According to the Intergovernmental Panel on Climate Change, when climate change alters ocean mixing, nutrient cycling is affected, altering the presence of plankton in different parts of the ocean.

The 2018 study that forecasted the shift of skipjack and yellowfin tuna to the eastern Pacific region used a numerical model, called spatial ecosystem and population dynamics model, that combines zooplankton, phytoplankton, and nutrient data with pelagic fish species’ known behaviors and needs. It analyzes how these interact with different climate change scenarios to forecast where the fish will likely go and how they will thrive.

Already Happening
The study also compared historical tuna fish yields in 1981 to 1990 and 2001 to 2010, and found that all four commercial tuna species had already begun to move gradually eastward. “This stuff has already happened,” Fitchett said.

Average sea surface temperatures in the western Pacific Ocean have increased by about 0.7 degrees Celsius since 1900 and are expected to keep rising. Under a high fossil fuel emissions scenario, average sea surface temperatures would be 1.2 to 1.6 degrees Celsius higher by 2050 and 2.2 to 2.7 degrees Celsius higher by 2100, relative to the 1980 to 1999 average.

Marine heat waves, which are lasting longer, have become more frequent and intense during the past few decades. The heat waves stress corals, causing them to lose their photosynthesizing symbionts, bleach, and possibly die. Coral bleaching endangers nearshore fish that spawn and live in these reefs.

Researchers at the Pacific Islands Fisheries Science Center found that, in a business-as-usual scenario of fossil fuel emissions, ocean warming will continue to cause severe coral bleaching, similar to what the Hawaiian Islands experienced in 2015. They also showed that severe coral bleaching could happen every year across much of Hawaiʻi in 2048.

This affects Hawaiʻi’s nearshore fishery, a mix of commercial and non-commercial fishers that catch pelagic and smaller reef fish. They sometimes sell these through the United Fishing Agency auction in Honolulu, but keep some of their catch to share with family and friends, or give away during important occasions.

Small boat commercial fishers in Hawaiʻi who fish near shore have reported declines in their catches. A survey by the Pacific Islands Fisheries Science Center showed a 53 percent decline in total catch of all pelagic fish from the mid-1990s to 2019. That’s from a peak of 7 million pounds in the 1990s to just 3 million pounds in 2019.

They also reported a steady decline in “deep 7 bottomfish”— so-called because they are seven species that live near the seafloor off the coast of Hawaiʻi and are important to the islands’ culture and economy. Total reported catch declined by 47 percent over the 30-year period, from a peak of 360,000 pounds in 1990 to around 190,000 pounds in 2019.

Finally, the total reported commercial catch of all nearshore fish increased from 1990 to 1998 but steadily declined by 68 percent the following years. The high was 1.9 million pounds in 1998, which decreased to just 600,000 pounds in 2019.

Scientists don’t currently have a clear understanding of what exactly has caused these changes. “There are many potential underlying reasons,” Gove said. “While total catch declined for the majority of fish groups within each of the fisheries over the past three decades, catch per trip did not show a commensurate drop. This is an area of active research that we will continue to pursue in the future.”

Invest, Divest, and Adjust
With so many changes expected to happen, how are Hawaiʻi and USAPI preparing? Fitchett says the WP Council is scheduling scenario-planning sessions this year and the following years, to be held in Hawaiʻi, American Samoa, and the Commonwealth of the Northern Mariana Islands. The council plans to involve scientists, longline operators, local fishing communities, and fish sellers and buyers.

“The objective is to look at viable possibilities for fishery resources, and how we can plan scientifically, but also logistically,” Fitchett said. “Should we start investing in fishery infrastructure elsewhere or should we start considering maybe divesting in certain species?”

For nearshore fishers, Gove at the Pacific Islands Fisheries Science Center has a more hopeful roadmap. When investigating the future onset of severe coral bleaching, Gove and his colleagues found that an effective global policy of reducing fossil fuel emissions gives much of Hawaiʻi a decade more before yearly severe bleaching hits its coral reefs.

“Our research showed that global climate policy may benefit coral reefs in Hawaiʻi by lengthening the time they have to adapt and acclimate to climate change,” Gove said. “The reality is though, most resource managers are not involved in writing global climate policy. But many local managers are directly involved in supporting or writing local policies, which can make a difference under ocean warming.”

In a recent study published in Nature, Gove and his colleagues showed that local management matters in conserving Hawaiʻi’s reefs and reef fish. Using data from the 2022 ecosystem status report, they showed that reefs that had increased coral cover over time had high fish biomass, particularly fish species that feed on fast-growing fleshy seaweeds. These healthier reefs also experienced lower levels of land-based stressors, like wastewater pollution and urban runoff. Reefs that declined in coral cover were exposed to much higher levels of land-based stressors and had low fish biomass.

“Our research found that simultaneously reducing local land- and sea-based human impacts benefits coral reef ecosystems under ocean warming,” Gove said. “Indigenous Hawaiian resource management stretched from the mountains (mauka) to the sea (makai) and was inclusive of the entire watershed, or ahupuaʻa. Our findings support the need for reintegrating both land and sea within coastal ocean management, akin to long-standing Indigenous stewardship of island ecosystems.”

Hawaiʻi and other Pacific Islands would also benefit from lessons learned by other countries and communities. A case study analysis of 18 small to large scale fisheries worldwide showed three attributes of climate-resilient marine fisheries. They harvested species with broad environmental tolerance and resilience to change. They had government systems that were responsive to change, operated efficiently, and were equitable and inclusive. Finally, they had access to a wide range of economic opportunities and were fairly flexible when it came to changing the way they used infrastructure, like boats and fish harvesting equipment.

The United Nations FishSCORE, a United Nations Ocean Decade Programme, is taking those lessons and co-developing a roadmap for fisheries to get to climate resilience. Claire Enterline, who leads the project, says it needs global collaboration and will take a decade to achieve.  She said, “The broader goal is to sustain fisheries as a source of food and jobs, while protecting ocean systems in the face of a changing climate.”

 

Browse Ka Pili Kai issues HERE