GROWTH OF THE OCEAN QUAHOG, ARCTICA ISLANDICA, IN 



THE MIDDLE ATLANTIC BIGHT 



Steven A. Murawski, John W. Ropes, and Fredric M. Serchuk 1 



ABSTRACT 



In situ growth rate of the ocean quahog, Arctica islandica, was investigated at a site 53 m deep off 

 Long Island, New York, during 1970-80. Specimens notched during summer 1978 and recaptured 

 1 and 2 calendar years later yielded information on shell growth and the periodicity of supposed 

 annual marks. Growth of specimens recaptured after 1 year at liberty (n = 67, 59-104 mm shell 

 length) was described by SL,.\ =2.0811 +0.9802 SL,, where SL is shell length in millimeters at 

 age t. Average shell length of marked specimens recaptured during summer 1980 increased 1.17 

 mm (w = 200), approximately twice that of ocean quahogs recaptured in 1979 (0.56 mm). Band for- 

 mation on the external surface of small ocean quahogs (less than about 60 mm) was apparently an 

 annual event since small specimens recaptured in 1979 formed one such mark during the interval 

 between release and recapture. Small specimens sampled during summer exhibited relatively 

 wide marginal growth from the last external mark to the shell edge, while winter samples had 

 formed new annuli at the shell margin, thus, external bands were formed during early autumn- 

 early winter. Internal banding in shell cross sections of small ocean quahogs correlated in number 

 and position with external features. An equation representing back-calculated growth, based on 

 external banding patterns of small unmarked specimens (19-60 mm) captured during summer 

 1978, was: SL = 75.68-81.31 (0.9056)', where tis age in years. Length-frequency samples were avail- 

 able for the vicinity of the marking study from routine dredge surveys of clam resources during 

 1970-80. Growth rates inferred from progressions of length-frequency modes in 1970 and 1980 sam- 

 ples were similar to those computed from mark-recapture and age-length equations. Ocean quahogs 

 are apparently among the slowest growing and longest lived of the continental shelf pelecypods; 

 annual increases in shell length were 6.3% at age 10, 0.5% at age 50, and 0.2% at an estimated age of 

 100 years. 



Research on the population dynamics of the 

 ocean quahog, Arctica islandica, has become in- 

 creasingly important in recent years. An inten- 

 sive fishery for the species developed off New 

 Jersey and the Delmarva Peninsula during the 

 mid-1970's. The resulting increases in U.S. land- 

 ings were dramatic: from 588 1 of shucked meats 

 in 1975 to a record 15,748 1 by 1979. Estimates of 

 the growth rate and longevity of ocean quahogs 

 inhabiting the Middle Atlantic Bight are neces- 

 sary to assess potential impacts of various har- 

 vesting strategies on the resources (Murawski 

 and Serchuk 2 ; Mid-Atlantic Fishery Manage- 

 ment Council 3 ). 



■Northeast Fisheries Center Woods Hole Laboratory, Na- 

 tional Marine Fisheries Service, NOAA, Woods Hole, MA 

 02543. 



2 Murawski,S. A., and F. M. Serchuk. 1979. Distribution, 

 size composition, and relative abundance of ocean quahog, 

 Arctica islandica, populations off the Middle Atlantic Coast of 

 the United States. ICES/CM. 1979/K:26, Shellfish Comm., 

 22 p. 



3 Mid-Atlantic Fishery Management Council. 1979. 

 Amendment No. 2 for the surf clam and ocean quahog fishery 



Several early studies alluded to the age and 

 growth rate of Arctica islandica, yet citations 

 were largely anecdotal and generally did not re- 

 flect critical evaluations of the rate of growth or 

 the validity of aging criteria. Turner (1949) 

 reported an observation by G. Thorson that 

 "European investigators who have studied the 

 chemical composition of the shell found reason to 

 believe that it took six years or more for mahog- 

 any (ocean) quahaugs (quahogs) to reach average 

 size." Loosanoff (1953) stated that ocean quahogs 

 he examined for reproductive studies "were 

 adults, several years old, and averaged 3% to 4 

 inches (89-102 mm) in length." Jaeckel (1952) 

 noted Cyprina (=Arctica islandica) could per- 

 haps attain ages up to 20 "Sie kann hohes Alter 

 (Vielleicht bis zu 20 Jahven) erreichen." Skula- 

 dottir 4 did not elaborate on aging methodologies 



Manuscript accepted August 1981. 

 FISHERY BULLETIN: VOL. 80. NO. 1. 1982. 



management plan and final supplemental environmental im- 

 pact statement. Mid-Atlantic Fishery Management Council, 

 Dover, Del., 114 p. 



4 Skuladottir, U. 1967. Kraffadyr og skeldyr (Crustacean 

 and mollusks). Radstefna Isl. Verkfraedinga. 52:13-23. 



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