Weathervane Scallop (Patinopecten caurinus)
Printer Friendly

General Description

The Alaska scallop fishery harvests the weathervane scallop, also called 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 or 'hinge' muscle to maintain this ability. This muscle is what is marketed as a "scallop," although it is only one part of the animal.

Size and sex determination

The biological measurement for scallop size 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 years. They spawn annually during summer and are about 100 millimeters in shell height when they are sexually mature. Sexes can be distinguished by gonad color; female gonads are orange-red to red, 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), broadcast spawners that reproduce by assembling and releasing clouds of gametes (eggs and sperm) which are fertilized in the water column. The signal for scallop spawning is thought to be increasing water temperature, which occurs in May and June in Alaska. Fertilized eggs settle to the bottom where they develop after a few days into a tiny transparent-shelled veliger larvae. Veliger larvae swim in the water column and feed on microplankton (small free-floating plants) for a period of about three weeks before settling to the bottom to begin 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 become commercially harvestable at about four inches shell height and age four to six years. 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; scallops lie on the rounder bottom valve, while the top valve is relatively flat.

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, sand or gravel substrate in depths of 120 to 390 feet. Adult scallops assemble in dense "beds" with a characteristic oblong shape that parallels the direction of the prevailing current.

Status, Trends, and Threats

Status

Commercial fisheries for weathervane scallops in Alaska are currently prosecuted 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. The long-term average harvest for 1993/94–2013/14 seasons is 601,901 pounds. . The federal overfishing level developed in 2012 is 1.29 million pounds of shucked scallop meats and the annual catch limit is 1.161 million pounds.

Threats

Primary threats to this species include habitat damage, ocean acidification, disease, and predation by crabs, seas stars and octopus.

Did You Know?

• The beauty of scallop shells has long been internationally recognized. Images of scallop shells are used to adorn items such as 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 Area, Cook Inlet Area, Kodiak Area, Alaska Peninsula-Aleutian Islands Area, and the Bering Sea Area. 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. Participants are encouraged to contact area offices prior to fishing for information on available fisheries, regulations, and nonsubsistence use areas.

Commercial Fishery

Scallops are captured commercially 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.

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 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 scallops onboard the vessels. Most scallops produced in Alaska are marketed directly by the cooperative. Except in the Cook Inlet Area, all commercial scallop fishing vessels are required by ADF&G to carry trained observers.

Personal Use Fishery

There are personal use scallop fisheries only in select locations of Alaska. A sport 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. Contact area offices for information.

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 Fishery Management Council (NPFMC) under the Magnuson Stevens Act and approved by the National Marine Fisheries Service in July 1995. The FMP was last updated and revised in 2005.

Management of the Alaska scallop fishery 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.

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 is responsible for the management of the onboard scallop observer program as well as conducting surveys using the Alaska CamSled. Homer and Cordova staff is 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 onboard observers to 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 are used to manage the scallop fishery in season, monitor crab bycatch, 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 vital to the management of the resource. In areas where fishery-independent assessment surveys occur, fishery data provides another perspective on 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 on topics such as scallop shell height-meat weight relationships, bottom temperatures, scallop meat quality, scallop genetics, tagging, and observations of marine mammals.

CamSled Surveys

Kodiak staff conducts surveys of scallop populations within beds in the Yakutat, Kodiak and Bering Sea areas using Alaska CamSled. CamSled is a high-speed megapixel benthic imaging system developed by the Alaska Department of Fish and Game. The towed, bottom-tending camera sled features a GigE Vision™ camera with a 1,000×1,200 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. Although CamSledwas developed for scallop stock assessment it is also useful for fine-scale habitat mapping, ground-truthing acoustic data, benthic ecology research, and fishing gear effects studies.

Dredge Surveys

Homer and Cordova staff conducts 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 1.5-inch mesh liner to facilitate 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 species, calculate a guideline harvest level based on the current estimated population size, and 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. 2014. Scallop Observer Training and Deployment Manual. Alaska Department of Fish and Game, Division of Commercial Fisheries, Kodiak.

Alaska Scallop Fisheries Management Plan (North Pacific Fishery Management Council)

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. 2014. Summary of observer data collected during the 2011/12 Alaska weathervane scallop fishery. (PDF 1,179 kB) Alaska Department of Fish and Game, Fishery Data Series No. 14-31, Anchorage.

Spafard, M. A., and G. E. Rosenkranz. 2014. Age and growth of Weathervane scallops Patinopecten Caurinus captured in the Alaska statewide scallop fishery, 1996-2013. (PDF 896 kB) Alaska Department of Fish and Game, Fishery Manuscript Series No. 14-03, Anchorage.

Scallop Plan Team (North Pacific Fishery Management Council)

General Information

• Weathervane Scallop — Wildlife Notebook Series (PDF 81 kB)