SIZE, AGE, SEXUAL MATURITY, AND SEX RATIO IN 



OCEAN QUAHOGS, ARCTICA ISLANDICA LINNE, 



OFF LONG ISLAND, NEW YORK 



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



ABSTRACT 



Ocean quahogs, A rctica islandica. were collected off Long Island. New York, in 1978 for a determination 

 of sexuality and gonadal condition. A microscopic examination of histologically prepared tissues of 133 

 clams. 19-60 mm in shell length, revealed that 36 were in an undifferentiated condition and could not be 

 sexed. Sexual differentiation was evident in 97 clams; of the latter, 69 were in two types of intermediate 

 development: those with sparse (20) and moderate (49) tubule development. Only 28 clams were fully 

 mature. Age and growth were assessed from acetate peels of shell cross sections. Determinations of sex 

 of these, and of specimens 57-103 mm in shell length collected from the same area in 1980. indicated 

 that the smallest and youngest ocean quahogs were predominantly male, but the largest and oldest 

 were predominantly female. 



Ocean quahogs, Arctica islandica, like most other 

 bivalves, lack external characteristics for a de- 

 termination of sex, maturation, and gonadal con- 

 dition. Sex determination has been made for other 

 bivalves, such as the surf clam, Spisula solidis- 

 sima (Ropes 1979a), from microscopic examina- 

 tions of gametogenesis in histological prepara- 

 tions of gonadal tissues. Similar examinations 

 were lacking for ocean quahogs. The resource has 

 become an important fishery within the past 

 half-decade (Ropes 1979b; Serchuk and Murawski 

 1980 2 ). 



In most bivalves that have been studied, sexual 

 maturity occurs at a young age and small size, but 

 species differences have been observed (Altman 

 and Dittmer 1972). Thompson et al. (1980a, b) 

 found that the ocean quahog is a slow growing, 

 long-lived species which exhibits considerable 

 variability in maturation with respect to size and 

 age. The latter conclusion was based on examina- 

 tions of 39 specimens, 87% of which were 40 mm or 

 longer in shell length. The samples were collected 

 in April-May, 3-4 mo before the spawning period 

 reported for this species by Loosanoff (1953). It 

 seemed reasonable to assume that mature, older 

 quahogs in the sample would produce large num- 



■Northeast Fisheries Center Woods Hole Laboratory. National 

 Marine Fisheries Service, NOAA, Woods Hole, MA 02543. 



2 Serchuk, F M.. and S. A. Murawski. 1980. Evaluation and 

 status of ocean quahogs, Arctica islandica (Linnaeus) popula- 

 tions off the Middle Atlantic coast of the United States. Woods 

 Hole Lab. Ref. Doc. 80-32. 4 p. Northeast Fisheries Center 

 Woods Hole Laboratorv, National Marine Fisheries Service, 

 NOAA, Woods Hole. MA 02543. 



Manuscript accepted September 1983. 

 FISHERY BULLETIN: VOL. 82. NO. 2. 1984. 



bers of sex cells, but it was not possible to deter- 

 mine whether most of the undifferentiated gonads 

 in the sample would do likewise. Their contribu- 

 tion to the reproductive potential of the species 

 was an enigma, and our knowledge of maturation 

 was incomplete. 



In late July and early August 1978, the National 

 Marine Fisheries Service marked large numbers 

 of ocean quahogs at a location near a site sampled 

 in the study of sexual maturity reported by 

 Thompson et al. (1980b). This was an opportunity 

 to collect specimens for a reexamination of 

 gonadal condition at about the time of maximum 

 ripeness, as Loosanoff (1953) had reported finding 

 many ocean quahogs in the partial spawning con- 

 dition in mid-August. The time of collection, then, 

 seemed favorable for obtaining sexually mature 

 quahogs with fully developed, ripe gonads that 

 could be clearly separated from immature 

 quahogs with undifferentiated sex cells in the 

 gonads. 



METHODS 



A commercial clam dredge vessel, MV Diane 

 Maria, was chartered for the marking project dur- 

 ing 25 July-5 August 1978. The hydraulic clam 

 dredge had a 100-in (2.54 m)-wide knife and was 

 modified by lining the inner surfaces with 1/2-in 

 (12.7 mm) square-mesh hardware cloth to retain 

 small clams. Sample tows were of 4-5 min duration 

 and usually resulted in a dredge filled with clams, 

 shells, and bottom substrata. 



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