In 2008, NOAA Fisheries implemented a catch share program for groundfish fisheries in the Bering Sea and Aleutian Islands, directly allocating the catch of several groundfish species, including rock sole, among sectors of trawl fishermen. This program allows fishermen in a specific trawl catcher/processor sector to harvest their shares together in a “cooperative.” This program has significantly improved retention and utilization of fishery resources, encouraged fishing practices with lower bycatch and discard rates, and helped increase the value of harvested species.
- Ocean perch
- Sea Bass
- Turbot (Greenland)
Lepidopsetta bilineata (Southern) and
L. polyxystra (Northern)
ALSO KNOWN AS:
Sole, Flounder, Rock Flounder, Two-lined Flounder, White-bellied Flounder
U.S. wild-caught from Alaska to California (but mainly Alaska)
- FISHING RATE
- HABITAT IMPACTS
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Southern rock sole. Rock sole is sometimes called roughback because of the rough scales on its back.LAUNCH GALLERY
Rock sole is not true sole, which is found only in the Atlantic, but is more closely related to flounder. In general, sole and flounder are delicate, mild-tasting fish. Rock sole’s roe is highly valued in Japan, so to supply this market it is mainly harvested in February and March, when females are bearing eggs. Alaska accounts for majority of the worldwide harvest of rock sole. In fact, along with yellowfin sole, the rock sole fisheries off Alaska are the largest flatfish fisheries in the United States. Most of their catch is shipped to Asia – females with roe go to Japan and males mainly go to China for processing and re-export to the United States.
There are actually two species of rock sole, northern and southern, found and harvested in U.S. waters of the North Pacific Ocean. Once heavily fished by foreign fleets in the 1960s, rock sole populations have recovered and are now well above target population levels. Scientists continue to actively monitor the abundance of both species of rock sole in the Bering Sea and Aleutian Islands region and the Gulf of Alaska. Managers use the latest estimates of abundance to set sustainable catch limits for the next fishing season. In the Bering Sea and Aleutian Islands, managers allocate the annual catch limit among participating permitted fishermen according to their historic harvest patterns and future harvest needs to improve retention and use of the available fishery resource. Catch is monitored throughout the fishing season to ensure it doesn’t exceed harvest limits or limits on bycatch of prohibited species (halibut, salmon, and crab).
LOCATION & HABITAT
There are two species of rock sole found in the North Pacific Ocean, a northern species (Lepidopsetta polyxystra) and a southern species (L. bilineata). Northern rock sole are found from Puget Sound through the Bering Sea and Aleutian Islands to the Kuril Islands (north of Japan). Southern rock sole are found from the southeast Bering Sea to Baja California.
Larvae are found in the upper 100 feet of the water column and juveniles move into deeper waters as they grow larger. Juveniles and adults live on the bottom and are found in shallow-water bays over the continental shelf as deep as 2,400 feet, but are uncommon below 985 feet. Adults and juveniles prefer sandy or gravel bottoms on the coast of the contiguous U.S. and also like steep rock slopes in Puget Sound. Some rock sole also prefer soft bottoms.
Rock sole are relatively sedentary. Immature rock sole reside in shallow waters and move to shallower waters in coastal areas in the spring and summer. Juveniles move into deeper water as they grow larger. Adults migrate to deeper waters in the winter to spawn and return in the summer to feeding grounds in shallow waters over the continental shelf.
Rock sole grow moderately slowly. They grow up to 2 feet long and can live for more than 20 years. They’re able to reproduce when they reach 4 to 7 years old. Northern rock sole spawn in midwinter and spring, and southern rock sole spawn in summer. Both populations spawn over a variety of surfaces, from rocky banks to sand and mud. Females lay eggs near the bottom, and the eggs stick to the surface on which they land. They hatch between 6 and 25 days later, depending on water temperature.
Larvae eat plankton and algae. Early juveniles eat zooplankton. Late juveniles and adults prey on bivalves, polychaete worms, amphipods, mollusks, and miscellaneous crustaceans. Larger fishes, including rock sole, feed on larval and juvenile rock sole. Sharks, marine mammals, and larger fishes feed on adults. The rock sole’s coloring and movements on the sea floor often confuse predators.
The rock sole is a flatfish. Most flatfish have both eyes on one side of their head. The southern rock sole’s blind (non-eyed) side is white with glossy highlights, but the northern rock sole’s blind side is creamy white, with no glossy highlights. Rock sole is sometimes called roughback because of the rough scales on its back.
Every 1 to 2 years, scientists in the NOAA Alaska Fisheries Science Center assess the abundance of flatfish such as rock sole in the Bering Sea and Aleutian Islands and Gulf of Alaska. The Science Center also runs an observer program for the Alaska groundfish fisheries. This program places fisheries observers on commercial fishing vessels to monitor and record catch and critical biological data (such as fish length, sex, and weight). This information improves our understanding of fishing activities and helps provide accurate accounts of total catch, bycatch, and discards associated with different fisheries and fish stocks.
In the Bering Sea–Aleutian Islands area, abundance of northern rock sole is very high, at over twice the target level. In the Gulf of Alaska, estimated abundance of both species is well above current catch levels.
Harvesting Rock Sole
Two species of rock sole—northern and southern—are caught within U.S. federal waters. The northern species (Lepidopsetta polyxystra) is more common in the Bering Sea and Aleutian Islands, where their catch exceeded 60,000 tons in 2011. Both species are found in the Gulf of Alaska and the southern species (L. bilineata) is also found off the West Coast.
Almost all of the U.S. commercial harvest of rock sole comes from Alaska, mainly the Bering Sea and Aleutian Islands area. Here, fishermen primarily use bottom trawls (a cone-shaped net towed across the bottom) to harvest rock sole. Because rock sole roe is highly valued in Asian markets, the majority (around 70 percent) of the harvest is caught in February and March when females are bearing eggs.
Who’s in charge? NOAA Fisheries and the North Pacific Fishery Management Council
Current management: Bering Sea and Aleutian Islands and Gulf of Alaska Groundfish Fishery Management Plans
- In Alaska, rock sole fisheries are managed separately, but similarly, in the Bering Sea and Aleutian Islands and in the Gulf of Alaska.
- Fishermen must have a permit to participate in these fisheries, and the number of available permits is limited to control the amount of fishing.
- Every year, managers determine how much rock sole can be caught.
- In the Gulf of Alaska, rock sole is managed as part of the shallow-water flatfish group along with several other flatfish species.
- In the Bering Sea and Aleutian Islands, over 10 percent of the catch quota is allocated to the Community Development Quota Program, which benefits fishery-dependent communities in western Alaska. The rest is allocated among the various fishing sectors based on gear type, vessel size, and ability to process their catch. Catch is monitored through record keeping, reporting requirements, and observer monitoring.
Only a small amount of rock sole is harvested incidentally in groundfish fisheries operating off the West Coast. The Pacific fishery management Council has included the species in the Pacific Coast Groundfish Fishery Management Plan, but it is neither assessed nor directly managed.
In the Bering Sea and Aleutian Islands, yearly domestic catches have averaged 47,600 tons for the past 2 decades. Rock sole remain moderately harvested in this area – the 2011 estimated catch of 60,400 metric tons was around 70 percent of the annual catch limit of 85,000 metric tons.
In the Gulf of Alaska, rock sole are lightly harvested. Annual harvests of northern and southern rock sole are usually less than 5,000 metric tons. In general, the flatfish fishery is limited by bycatch limits for Pacific halibut.
A small amount of rock sole are harvested incidentally in fisheries for other groundfish off the West Coast.
Approximately 80 to 90 percent of the sole harvested in the Alaska groundfish fisheries is shipped to Asia. Rock sole are the target of a high-value roe fishery, which accounts for the majority of the annual catch in the Bering Sea–Aleutian Islands area. Rock sole with roe are exported to Japan, where they are sold whole with their roe as a supermarket staple.
Male rock sole are exported to China, where they are filleted and exported back to the United States. Chinese re-processors tend to export fillets of small rock sole and yellowfin sole in the same pack.
Rock sole have a mild, sweet flavor with small tender flakes and a medium texture. Like all flatfish, its fillets are thin.
Rock sole is an excellent source of low-fat protein, calcium, and other important nutrients.
|Serving Weight||100 g|
|Fat, total||1.19 g|
|Saturated fatty acids, total||0.283 g|
|Sugars, total||0 g|
|Fiber, total dietary||0 g|
Rock sole table of nutrition
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