Conservation & Environment

August 17, 2022 — The following was released by NOAA Fisheries:

Following international action to end overfishing of Pacific bluefin tuna, a new stock assessment shows that the species is now increasing and includes many younger fish that will help accelerate its rebound. The new assessment was presented at a recent plenary meeting of the International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean (ISC).

The assessment confirmed that the stock surpassed the first rebuilding target in 2019. It is projected to likely increase beyond the second rebuilding target established by the Inter-American Tropical Tuna Commission and Western and Central Pacific Fisheries Commission later this year. This is well ahead of the internationally agreed schedule.

“The new findings demonstrate the resilience of a species that can multiply quickly when given the chance,” said Kevin Piner, a research fishery biologist at NOAA Fisheries’ Southwest Fisheries Science Center who led work on the stock assessment for the United States. It also reflects the strength of the current stock assessment and projections that incorporate decades of information on Pacific bluefin biology and fisheries. It also demonstrates coordinated management action by nations including the United States, Japan, Korea, Chinese Taipei and Mexico.

“The species has responded exactly as we predicted it would given the actions that were taken,” he said. “This is an amazingly resilient fish and it is now showing us that.”

He noted that while the trend is positive and accelerating, monitoring must continue to ensure the stock meets the second rebuilding target. Pacific bluefin tuna support U.S. commercial and recreational fisheries off the West Coast. However, the U.S. catch represents a small share of the combined international catch.

Coordinated Action Takes Hold

Many fish such as bluefin are assessed based on their unfished spawning stock biomass—the theoretical amount of fish if there was no fishing. Catches reduced the bluefin biomass through the late 1990s and 2000s to only a few percent of its potential unfished biomass. Recent stock assessments predicted that reducing fishery catch on younger fish would lead to a rebound in biomass within just a few years.

“We had confidence that the coordinated international actions to manage fishing impacts based on what the science showed us would put us on the right track,” said Ryan Wulff, who leads the U.S. delegation to the Inter-American Tropical Tuna Commission, and serves as Assistant Regional Administrator for Sustainable Fisheries for NOAA Fisheries’ West Coast Region. “This is why we invest in research to understand the species and we take a Pacific-wide approach.”

Beginning in 2011, the Western and Central Pacific Fisheries Commission began management measures that reduced the catch of smaller bluefin and limited the catch of larger bluefin. This allowed more fish to grow to maturity. These measures reflected the U.S. interest in rebuilding the stock while also recognizing that some communities rely on bluefin and need continued fishing opportunities.

The Inter-American Tropical Tuna Commission adopted a similar resolution to limit catches a year later in its management area. Since then, the two Commissions have coordinated across the Pacific, using the best available science to inform management decisions across the entire range of the species. In 2013, based on the 2012 ISC stock assessment, NOAA Fisheries determined that Pacific bluefin tuna were overfished and subject to overfishing.

In 2016, increasing concern about declining biomass levels led to a petition to list the species as endangered. NOAA Fisheries determined that while the population was near historical lows, the roughly 1.6 million fish was sufficient to avoid risk of extinction and protect against the effects of small populations.

NOAA Fisheries formed a team to consider the status of the species in light of the petition. The team determined that international agreements and management changes should reduce the impact of commercial and recreational fisheries, particularly the impact on younger fish. That would reduce landings and help rebuild the population, the team found.

Younger Fish Accelerate Growth

The new stock assessment confirmed what past stock assessments predicted. After declining from 1996 to 2010, the spawning stock biomass has increased since 2011. Fishing limits allowed younger fish to multiply, reaching the first rebuilding target adopted by the Western and Central Pacific Fishery Commission in 2019. The more numerous younger fish will grow in size, increasing the rate at which the biomass will increase and could reach the second rebuilding target as soon as this year.

The stock is recovering faster than anticipated, and met the initial rebuilding target, 5 years ahead of the 2024 deadline, said Dr. Huihua Lee, a research mathematical statistician at NOAA Fisheries’ Southwest Fisheries Science Center. She helped develop the stock assessment. “The success reflects the coordinated science-based management measures to reduce catches of young fish and the strong resilience of the species,” she said.

The rebuilding strategy applied what fisheries managers had learned from research into the life history, genetics and migration patterns of the iconic species, noted Kristen Koch, director of the Southwest Fisheries Science Center and acting Chief Scientist of NOAA Fisheries. “That legacy of science showed us how we needed to work across boundaries and really across the Pacific Ocean to effectively turn things around for the species,” she said.

Read the full release here

August 17, 2022 — The following was released by NOAA Fisheries:

Conservation and management of shark populations is increasingly important on a global scale because many species are vulnerable to overfishing. Internationally protected shark species remain at risk due to bycatch in commercial fisheries. In the western Pacific Ocean, oceanic whitetip and silky shark populations are overfished. Oceanic whitetip sharks are also experiencing overfishing, and were listed as threatened under the U.S. Endangered Species Act in 2018. Recent research has shown that switching to a new type of fishing gear can drastically reduce bycatch for these species.

What is Bycatch?

Bycatch is when non-targeted or protected species are accidentally captured during commercial fishing operations. It threatens seabirds, sea turtles, whales, dolphins, sharks, and rays globally. Oceanic whitetip and silky sharks are inadvertently caught as bycatch in pelagic longline fisheries targeting tuna, like the Hawai‘i deep-set longline fishery.

Bycatch Reduction Measures in the Pacific

Several regional fisheries management organizations have undertaken steps to reduce bycatch-related mortality of oceanic whitetip and silky sharks. This includes measures implemented by the Western and Central Pacific Fisheries Commission that prohibit fishermen from retaining these sharks or their fins and require sharks be handled and released as soon as they are brought alongside the vessel in a manner that minimizes harm.

Hawai‘i deep-set longline fishing vessels are now required to use leaders composed of monofilament material, rather than wire, to reduce mortality of captured oceanic whitetip sharks. The fishermen are also required to remove the hook, or, if they are unable to do so, to cut the fishing gear as close to the hook as possible. Cutting monofilament leaders is much easier than cutting wire leaders. This gear and operational change was initiated by the Hawai‘i Longline Association, whose members, more than 90% of the Hawai‘i longline fleet, voluntarily transitioned to monofilament leader material before the regulations went into place. Researchers found that sharks could bite through monofilament gear and free themselves more quickly and easily than if they were caught on wire leaders.

Gear Modification Research

Drs. Molly Scott, Melanie Hutchinson, and Jennifer Stahl at the Cooperative Institute for Marine and Atmospheric Research tested different gear configurations for Hawaii longline fishing vessels with co-authors from the University of Hawai‘i. The goal was to reduce injury and mortality to bycaught species. They compared catch rates and condition (e.g., alive, dead, level of injury) of target and non-target species after capture on either wire or monofilament leaders. They also tested different configurations (size, diameter, shape, metal type, and leader material). This helped determine the amount of strength required to either break or open the hook, and the time taken for trailing gear to deteriorate.

Their research was recently published in the journal of Marine Policy. They found that switching from wire to monofilament leaders reduced the mortality rate of sharks by approximately 41 percent and still maintained catch rates of target species (bigeye tuna). Branchlines with wire leaders began to deteriorate after approximately 60 days, but hooks with monofilament leaders did not break apart, even after 360 days. Additionally, the breaking strength of fishing hooks was greater for larger, forged stainless steel hooks typically used in U.S. Pacific longline fisheries.

This study suggests that using a combination of monofilament leader material with smaller, galvanized, unforged hooks can reduce the amount of force required to straighten or open a hook by up to 70 percent. Dr. Scott shared, “This combination of gear can substantially reduce injury and mortality of sharks and many other species, including protected species such as false killer whales. We strongly support the Hawai‘i Longline Association and their voluntary transition from wire to monofilament leaders. We also want to highlight the importance of removing as much trailing gear as possible from the animals (including the weights) to prevent further injury.”

Read the full release here