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Weathervane Scallop (Patinopecten caurinus)
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Did You Know?

There are around 350 species of scallop in the family Pectinidae.

General Description

The Alaska scallop fishery is based upon the weathervane scallop, also called the giant Pacific scallop, scientific name Patinopecten caurinus. Unlike most bivalves (clams and mussels), scallops cannot burrow to escape predation, but instead they detect predators with primitive 'eyes' and have limited ability to swim away by rapid opening and closing of their shells. Scallops require a very large adductor, ‘hinge’ muscle, to maintain this ability. This muscle is what we think of as a "scallop," although it is only one part of the animal.

Size and sex determination

The biological measurement for scallops is shell height. This is measured from the base of the hinge to the edge of the scallop shell. Weathervane scallops sexually mature around age 3 or 4. They spawn annually, usually in early summer and are about 100 millimeters in shell height when they are sexually mature. The sexes can be distinguished by the color of the gonads; female gonads are orange-red to red in color, and male gonads are creamy white. Otherwise, male and female gonads are similar in size and shape.

Similar species

There are other scallop species in Alaskan waters, but none as large as the weathervane scallop. These include: Pacific pink scallop, Chlamys rubida; spiny pink scallop, C. hastata; white scallop, C. albida; arctic pink scallop, C. behringiana; C. islandica; purple-hinged rock scallop, Crassadoma gigantea; Vancouver scallop, Delectopecten vancouverensis; and Alaska glass-scallop, Parvamussium alaskense.

Life History

Growth and Reproduction

Scallops are dioecious (have two sexes), are broadcast spawners, and reproduce by assembling and releasing clouds of gametes (eggs and sperm) which are fertilized in the water column. The signal for scallops to assemble and spawn is thought to be increasing water temperature, and in Alaska spawning occurs in May and June. Fertilized eggs settle to the bottom where they develop after a few days into a tiny transparent-shelled veliger larvae. The veliger larvae swims into the water column where it feeds on microplankton (small free-floating plants) for a period of about three weeks before settling to the bottom to begin its life as a benthic (bottom-dwelling) filter feeder.

Weathervane scallops begin to reproduce at three or four years of age at a shell height of about three inches, and are of a commercially harvestable size at about four inches shell height and six to eight years of age. Scallops reach a maximum age of approximately 28 years in Alaska. Like other bivalve mollusks, scallops are aged by counting the rings on their shell, which are formed by alternating periods of slow and fast growth associated with seasonal changes in temperature and food availability. The two valves of scallop shells are not identical, and the scallop body lies on the bottom valve, which is more rounded in shape, while the top valve is flatter.

Range and Habitat

Weathervane scallops are distributed from California to the Bering Sea and as far west as the Aleutian Islands. Scallop beds in Alaska are located on mud, clay, sand or gravel substrate in depths of 120 to 390 feet. Adult scallops assemble in dense "beds"; these have a characteristic oblong shape, with the longer axis parallel with the direction of the prevailing current.

Status, Trends, and Threats

Status

Commercial fisheries for weathervane scallops in Alaska are currently prosecuted in offshore waters from Cape Spencer in Southeast Alaska to north of Unimak Island in the Bering Sea.

Trends

Historical harvest of weathervane scallops in Alaskan waters peaked at 1.85 million pounds of shucked scallop meats in the 1969/70 season. A second peak of 1.79 million pounds occurred in the 1992/93 season. The long-term average harvest for 1967–2010/11 seasons is 703,590 pounds, and the 40, 30, 20, and 10-year averages are 703,590; 669,024; 697,854; 714,080; and 476,117 pounds respectively. An optimum yield of 0 to 1.8 million pounds of shucked scallop meats was established in 1996. In 1998, optimum yield was redefined as 0 to 1.24 million pounds. The 2012 Scallop Stock Assessment and Fishery Evaluation Report found that statewide scallop harvests have not exceeded the upper limit of optimum yield and thus are not overfished.

Threats

The primary threats to this species include habitat damage, ocean acidification, overfishing, and predation by crabs, seas stars and octopus.

Did You Know?

  • The beauty of scallop shells has long been internationally recognized. The image of scallop shells is used to adorn everything from postcards, stamps, family crests, oil company logos, and trail signs along the Camino de Santiago walking pilgrimage in Spain.
  • There are around 350 species of scallop in the family Pectinidae.

Uses

Subsistence Fishery

Alaska Administrative Code, Chapter 2 provides for subsistence harvest of scallops in state waters of Southeast Alaska, Prince William Sound, Cook Inlet, Kodiak Area, Alaska Peninsula-Aleutian Island Area, and the Bering Sea Area. Bag limits and seasons are generally more liberal and gear requirements less restrictive than for personal use or sport fisheries. Unlike personal use fishery catch, which may be shared only with immediate family members, subsistence fishery catch may be shared with all members of the community.

Commercial Fishery

Scallops are captured using standard New Bedford style scallop dredges that are on average 15 feet wide and weigh about 2,600 pounds. The frame provides a rigid, fixed dredge opening to which a steel ring bag (consisting of 4-inch rings linked together) is attached to collect the scallops as the dredge is towed. In response to an influx of vessels from the east coast, a vessel moratorium was implemented in state waters in 1997; eight vessels currently hold vessel-based entry permits. In a further effort to increase economic efficiency, permit holders created a scallop fishing cooperative in 2000. Some cooperative members opted to remove their boats from the fishery and arranged for their shares to be caught by other members of the cooperative, providing the remaining vessels with additional fishing opportunity. In recent seasons, only four vessels on average have participated in the fishery. This fleet of 70 to 120-ft vessels each has a crew of eight to twelve, who shuck and freeze the scallops onboard the vessels. Most of the scallops produced are marketed directly by the cooperative. Except in the Cook Inlet area, all commercial scallop fishing vessels are required to carry trained observers.

Personal Use Fishery

There are personal use scallop fisheries around the state of Alaska. A sports fishing license is required for participation. There is no closed season, but permits are required in some areas while bag and possession limits are established for others.

Management

The scallop fishery in Alaska is jointly managed by the State of Alaska and the federal government under the Alaska Scallop Fishery Management Plan (FMP). Most aspects of scallop fishery management are delegated to the state, while limited access and other federal requirements are under jurisdiction of the federal government. The FMP was developed by the North Pacific Fisheries Management Council (NPFMC) under the Magnuson Stevens Act and approved the National Marine Fisheries Service in July 1995. The FMP was last updated and revised in 2005.

In season, management of Alaskan scallop fishery harvest is achieved using "guideline harvest levels" (GHLs), which are established at the beginning of each fishing season. In addition to GHLs, most scallop fisheries have crab bycatch limits. Fisheries are closed when either GHLs or bycatch limits are met. Large areas of productive scallop habitat are also closed to scallop dredging as an additional precautionary measure to maintain fishery productivity.

The management regime requires preseason, in season, and long-term information. Preseason information on population size and health is needed to set biologically appropriate GHLs. In season, observers regularly submit information on scallop harvest and crab bycatch which is used to close the fishery when limits are met. Information on scallop biology (growth rates, size at maturity, and maximum age) is needed to help evaluate stock condition and productivity to further refine regulations.

Research

Research on weathervane scallops is conducted by ADF&G staff in Kodiak, Homer and Cordova. Kodiak staff are responsible for the management of the onboard scallop observer program as well as conducting surveys using the Alaska CamSled. Homer and Cordova staff are responsible for conducting surveys in Kamishak Bay in lower Cook Inlet, and at Kayak Island in the Gulf of Alaska using an 8-foot wide dredge.

Onboard Observer Program

Onboard observers have been required on all commercial vessels fishing for weathervane scallops in Alaska waters excluding Cook Inlet since 1994. Scallop fishery observer coverage is funded by industry through direct payments to independent contracting agents who provide the onboard observers to the vessels. ADF&G coordinates observer activities including training, deployment, briefing, debriefing, and certification, and maintains a database of observer-collected data at the Kodiak office. Data collected from the scallop fishery are used to manage the fishery in season, monitor crab bycatch and ensure established crab bycatch caps are not exceeded, provide for regulatory enforcement, and answer a host of questions about catch composition, bycatch, habitat, and the health of the scallop resource. These data are necessary to achieve the requirements set out in the Magnuson-Stevens Act and the Alaska scallop FMP including the sustained yield of the shellfish resource without overfishing. In most areas of the state, the department does not conduct scallop stock assessment surveys, so observer-collected data are even more vital to the management of the resource. In areas where fishery independent assessment surveys do occur, fishery data provides another perspective on the health of the stock. The scallop observer program also provides an opportunity for various research projects to be conducted. Depending on the research goals, observers are assigned special projects to collect data for topics such as scallop shell height to meat weight relationships, bottom temperatures, weak scallop meats, scallop genetics, tagged animals, endangered birds and observations of marine mammals.

CamSled Surveys

Kodiak staff conduct surveys of scallop populations within beds in the Yakutat, Kodiak and Bering Sea areas using the Alaska CamSled. The CamSled is a high-speed megapixel benthic imaging system developed by the Alaska Department of Fish and Game with design assistance from Wood's Hole Oceanographic Institution's HabCam project. The towed, bottom-tending camera sled features a GigE Vision™ camera with a 1360×1024 pixel sensor that streams 16 MB/s of image data to the tow vessel over commercial off-the-shelf Gigabit Ethernet hardware and an armored fiber optic tow cable. The camera images a 1.1 x 0.83 meter area of the bottom four times per second under strobe lighting that eliminates blurring in the images (motion artifacts) while towing at 5 to 8.5 km/h. The camera sled was developed for scallop stock assessment but is also useful for fine-scale habitat mapping, ground-truthing acoustic data, benthic ecology research, and fishing gear effects studies as well.

Dredge Surveys

Homer and Cordova staff conduct biennial area-swept dredge surveys on the north and south scallop beds in Kamishak Bay, and on the east and west scallop beds at Kayak Island using an 8-foot wide dredge with a retainer bag fitted with a 1.5-inch mesh liner to facilitate the retention of small scallops. Survey objectives are to assess scallop abundance and biomass, document scallop age and shell height compositions, estimate scallop meat recovery rates, determine the relative catch of king and Tanner crab and other non-scallop species, calculate a guideline harvest level based on the current estimated population size and also to evaluate changes in scallop distribution and density over time. The first scallop survey in Kamishak Bay was conducted in 1984 and since 1996, surveys have been conducted in Kamishak Bay and at Kayak Island on alternating years.

Get Involved

Alaska Board of Fisheries

Management of fisheries in state waters is achieved through regulations promulgated by the Alaska Board of Fisheries (BOF). The BOF holds regular meetings to revise old regulations or promulgate new ones and takes input from stakeholders at these meetings. For BOF meeting schedules, agendas, proposals, forms, and contact information please visit the Board of Fisheries webpage.

More Resources

Licenses and Permits

For commercial fishing licenses and permits including crewmember, catcher-seller, direct marketers, buyers, exporters, processors, transporters, and reporting, please visit the Licenses & Permits section of our website.

For commercial fishing entry permits, and intent to transfer forms please visit the Alaska Commercial Fisheries Entry Commission (CFEC) website.

Fishery Openings/Updates

For commercial fishing regulation announcements, news releases, and emergency orders, please visit our Regulation Announcements, News Releases & Emergency Orders page.

To search for scallop-specific news releases on this webpage, choose "Shellfish-Misc" from the drop down menu under the Species Group search criteria.

References

Alaska Department of Fish and Game Shellfish Observer Program. 2012. Scallop Observer Training and Deployment Manual. Alaska Department of Fish and Game, Division of Commercial Fisheries, Kodiak.

Alaska Scallop Fisheries Management Plan

Gustafson, R. L., and K. J. Goldman. 2012. Assessment of weathervane scallops in Kamishak Bay and at Kayak Island, 2004 through 2012. (PDF 2,077 kB) Alaska Department of Fish and Game, Fishery Data Series No. 12-62, Anchorage.

Rosenkranz, G. E., and M. Spafard. 2011. Summary of observer data collected during the 2009/10 Alaska weathervane scallop fishery. (PDF 1,888 kB) Alaska Department of Fish and Game, Fishery Data Series No. 11-70, Anchorage.

Scallop Plan Team

General Information

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