1571 



Ropes, John W. 1971. 



Maryland's hard clam studied at Oxford Laboratory. Coiran. Fish News, Md. Fish 

 Wildl. Admin. 4(6): 2-3. 



Bays and estuaries of the Atlantic Ocean side of the Delmarva Peninsula have 

 averaged 1.5 million pounds of meat production per year from Mevcenavia 

 mevcenavia in the decade 1960-69; Chesapeake Bay only about 800,000 pounds. 

 The hard clam industry was presented with two alternatives: to increase 

 selective fishing pressure on smaller, more valuable, clams, or to grow young 

 clams artificially in hatcheries under controlled conditions. It was feared 

 that present markets for small clams might destroy brood stocks needed for 

 natural replenishment. To identify sex of a hard clam, thin sections of tissue 

 must be examined under a microscope. During spawning, sex cells are carried to 

 the surrounding water through the siphon. Sex products are forced out 

 rhythmically by the powerful adductor muscles. A few clams ripened by mid- 

 June, but spawning was delayed until late June-early July after water temp had 

 dropped to 25°C, then rose to 29°C. Spawning probably continued through July. 

 Threshold temp for spawning in Chincoteague Bay is 25° to 30°C. Spawning 

 temps are lower farther north, suggesting the Chincoteague Bay quahogs are 

 different phsiologically . This could add to the cost of artificial 

 propagation. - J.L.M. 



1572 



Ropes, John. 1976. 



NMFS studies new offshore clam resource: The ocean guahog. Coram. Fish. News, 

 Md. Dept. Natural Resources 9(6): 1, 4. 



Describes in some detail what is known about Avotica islandiaa, the ocean 

 quahog, including spawning, temp requirements, distribution, and history of 

 the fishery. Meveenaria mevcenavia is mentioned. - J.L.M. 



1573 



Ropes, John W.,and Charles E. Martin. 1960. 



The abundance and distribution of hard clams in Nantucket Sound, Massachusetts, 

 1958. U.S. Dept. Interior, Fish Wildl. Serv. , Spec. Sci. Rept. - Fish. 354, 

 12 p. 



At the request of the Atlantic States Marine Fisheries Commission, a survey 

 was made of Venus (Mevcenavia) meveenaria stocks in Nantucket Sound. The gear 

 was a hydraulic dredge such as was used in the surf clam fishery. Population 

 densities were very low. No hard clam less than 6 mm long was taken, even 

 with a fine lining in the dredge, or with a clam-shell bucket. No new hard 

 clam beds of commercial importance were found. Sizes were very uniform and 

 large, average length 111 mm (4 3/8 inches), and 95% were between 94 and 

 127 mm. Average population densities for the 3 major areas were 0.7, 0.6, 

 and 0.5 clams/100 f t 2 . Greatest density in any single tow was 11 clams/11 ft 2 . 

 Estimated ages were 15 to 30 yrs . Growth was slow. It was concluded that this 

 stock was an accumulation of a few offspring that survive each year. A 

 commercial fishery was possible only because the hydraulic dredge is so 

 efficient. Densities of hard clam stocks reported in the literature 



(abstracted elsewhere in this bibliography) for Chincoteague Bay, Md. and 

 Narragansett Bay, R.I. were much higher. Bottom water temps in Nantucket 

 Sound seldom reach 69°F, which has been reported as the minimum temp for 

 spawning. Thus, spawning in the Sound may occur only in those rare years 

 when water temp rises above this level. Sampling showed that the following 

 hard clam predators were present: Busycon eanaliculatum and B. oavica, Lunatia 



(Polinices) hevos and P. duplicatus, Astevias sp. and Limulus polyphemus . 

 The future of the hard clam fishery in Nantucket Sound was judged uncertain. 

 - J.L.M. 



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