Yellowfin sole is the target of the largest flatfish fishery in the U.S. by volume and it is the smallest commercial flatfish species in the North Pacific with a harvest length around 18". Most yellowfin sole weighs less than a pound so it’s usually sold as thin two- to four-ounce fillets. Yellowfin sole has a firm, delicate texture with small flakes and when cooked and a mild, sweet flavor. It is available throughout the year, primarily as frozen skinless, boneless fillets. It is almost always frozen H&G at sea and processed in China into fillets before being sold in the U.S. Quality of Pacific flatfish, including yellowfin sole, varies greatly so it’s important to look for unbruised fillets that have uniform color. Purchasing whole yellowfin sole should only be done if the buyer has a way to negotiate with the supplier since there can be a high percentage of soft-flesh fish.
Key sustainability sourcing notes for yellowfin sole based on landings from 2013-2016 and the most recent 2014 Seafood Watch assessments (Alaska) and 2015 MSC certification (Alaska - Bering Sea Aleutian Islands):
~100% of yellowfin sole landings from Alaska meet both a Seafood Watch "Best Choice (green)" rating and is MSC-certified
Yellowfin sole from Alaska has been certified by the MSC since 2010 and is currently certified until 2020
Prior to October 2014, yellowfin sole from Alaska had a Seafood Watch "Good Alternative (yellow)" rating
Yellowfin sole landings peaked in 2013 at ~350 million lbs., and landings in 2016 saw a decrease of ~15% compared to 2013
Yellowfin sole are a flatfish with a small mouth and both eyes located on one side of their body. Yellowfin sole get their name from their yellow-colored fins. These fins also have faint dark bars, with a narrow dark line at the base. Their bodies are typically rounded with a rounded tail fin. The upper side where their mouths and eyes are located is an olive to dark brown with dark mottling and their underside is pale. Rough scales cover both sides of the body. Yellowfin sole can grow up to over 1.5 feet long and can weigh upwards of a pound. The species is also long-lived, with a lifespan of up to 39 years.
Adults spawn in the spring and summer months, migrating from the outer continental shelf to the shallow waters along the inner shelf. These shallow waters act as nursery grounds for settled juveniles. During spawning periods, females have a high reproductive potential and can produce between one and three million eggs. Females are able to reproduce around the age of 10.5 years (when they are approximately one foot long).
Yellowfin sole are opportunistic feeders and their diet depends on their life stage. Larvae and early juveniles feed on plankton and algae. Late-stage juveniles and adults eat bivalves, amphipods, mollusks, krill, shrimp, brittle stars, sculpins, and various other crustaceans. Pacific cod and halibut prey on juvenile yellowfin sole.
Yellowfin sole are distributed off the Pacific coast of North America from British Columbia to the Bering Sea and north to the Chukchi Sea. The majority of the US stock occurs on the eastern Bering Sea shelf and, subsequently, the major yellowfin sole fishery occurs there. They also can be found across the Pacific, off the coast of South Korea to the Sea of Japan and to the Sea of Okhotsk. Adults are benthic and live on soft, sandy ocean bottoms up to depths of 2300 feet (700 meters) – though most are found around 299 feet (91 meters) deep. Yellowfin sole occupy different winter, spawning, and summer distributions on the eastern Bering Sea shelf. Adults will spend the winter months near the outer shelf margins in deeper waters and will move to the inner shelf and to shallow waters less than 98 feet (30 meters) in the spring to feed and spawn.
Science & Management
Yellowfin sole is one of the more abundant flatfish in Alaska’s waters and thus have been well-studied by the Alaska Fisheries Science Center (AFSC). Much of the center’s research currently focuses on estimating biomass of yellowfin sole through the use of mathematical models. The AFSC hopes to address how uncertainty affects various model parameter estimates and study how much catch rates have changed over the past 28 years.
The AFSC also conducts stock assessments for yellowfin sole using information on catch data, biomass estimates, and age composition of catch data and biomass estimates. Studies on the status of the yellowfin sole in the Bering Sea show that the species is not overfished and biomass has remained high and stable in recent years. Scientists are also using new technological advances that measure fishing vessels’ catch to begin to compare fishery weight-at-age datasets.
Yellowfin sole are considered to be one of the most abundant flatfish species in the Bering Sea where they are the target of the largest flatfish fishery in the U.S.. NOAA Fisheries and the North Pacific Fishery Management Council (NPFMC) manage the yellowfin sole fishery in the Bering Sea under the Fishery Management Plan (FMP) for Groundfish of the Bering Sea/Aleutian Islands. In addition to yellowfin sole, the FMP sets management measures for Pacific cod, Alaskan pollock, other soles, and various flounder and rockfish species. Yellowfin sole, along with rock sole, flathead sole, arrowtooth flounder, Alaska plaice, and other flatfish species are caught using bottom trawl gear in this fishery. Amongst management measures included in the plan for yellowfin sole include:
An annual total allowable catch (TAC) limit for yellowfin sole – with a proportion of this TAC (10.7 percent) set aside to a community development quota program;
Requirements that all yellowfin sole caught be retained; and,
Monitoring and catch reporting requirements including observer coverage.
Additionally, there are bycatch limits in place for the groundfish fishery for halibut and crab. Should this limit be exceeded by the groundfish fishery, fishery managers will close the fishery for the rest of the season. Fishers must also abide by closed areas that have been established by NOAA and the NPFMC to protect sensitive habitats from bottom trawling. According to a 2016 stock assessment, yellowfin sole in the Bering Sea/Aleutian Islands are not overfished nor subject to overfishing.
Yellowfin sole are also managed under the FMP for Groundfish of the Gulf of Alaska. While yellowfin sole dominates the flatfish fishery in the Bering Sea, they are considered to be relatively scarce in the Gulf of Alaska. They are; however, still included in the FMP for Groundfish of the Gulf of Alaska as part of the shallow water flatfish complex. Only a small amount of yellowfin sole are caught in Gulf of Alaska, and that is made up entirely of incidental catch. The shallow water flatfish complex in the Gulf of Alaska is not overfished nor subject to overfishing according to a 2016 stock assessment.
Yellowfin sole is a type of flounder that is slow growing, long-lived and greatly affected by changing environmental conditions, making it vulnerable to fishing pressure. However, its wide distribution over much of the North Pacific helps counterbalance these traits somewhat.
Yellowfin sole, which is primarily harvested in the United States, is the largest flatfish fishery in Alaska due to its abundance. Although yellowfin sole was harvested heavily in the 1950s and ’60s, its population has recovered to above target levels.
Habitat impacts (Wild)
Factory trawlers in the Bering Sea off Alaska are the primary means of catching yellowfin sole. Trawling tends to be highly destructive to seafloor habitats but yellowfin sole typically dwell in sandy, muddy bottom habitats that require little rebuilding to recover compared to rocky or reef areas.
Bycatch in the yellowfin sole fishery is considered low, and does not include overfished species. Restrictions are in place to keep bycatch low, and according to the Environmental Defense Fund, better gear design is helping trawlers avoid areas where bycatch will be more likely.
Successful management measures helped yellowfin sole reach high levels of abundance. Substantial fishery management measurements remain in place in the North Pacific, including close catch and bycatch monitoring, calculated catch limits, and independent population assessments.