493 



Dow, Robert L. 1971. 



4. Natural yields of certain species. Second of two articles describing the 

 "Renewable Marine Resource Industry Potential in Maine", under the heading 

 "Dow Sees Maine Aquaculture Worth Far More Than Existing Industries". Natl. 

 Fisherman 51(11): 1-C, 4-C. 



Orr's Cove, Harpswell, surveyed on 25 Aug 1953, had 1952 year-class hard clam 

 concentrations ranging from to 80,000 clams/ft2 of bottom. Two portions of 

 the Cove, about 30,000 ft2 in area, had an average population of about 

 40,000 quahogs/ft2. This was 1.2 billion clams with an average diameter of 

 4 mm. Transplants of quahogs to below mean low water have survived 90% or 

 more annually. Natural concentrations above mean low water survived 10% or 

 less. Survey of Avery's Cove in Sept 1952 gave an estimate of 139.8 million 

 quahogs of the 1952 year class, 3 mm in diameter on the average, on 10.7 

 acres. Survey in Brickyard Cove in Aug 1953 showed residual concentrations of 

 1952 year-class hard clams of 1,000 to 1,400 live clams/ft2 on an area greater 

 than 5 acres. Average size was 6 mm, and the population was estimated at 

 261.36 million clams. In a 3-yr period the 1952 year class of hard clams in 

 Middle Bay produced 429 bu of clams, or 4,719 lbs of shucked meats/acre/yr . 

 From Sept 1955 to Apr 1960 an area at West Bath produced 36,751 lbs of hard 

 clam meats from 6 acres. In addition, 13,600 bu were transplanted to un- 

 occupied growing areas. Spectacular sets of hard clam occurred in many 

 growing areas in Maine in 1947 and 1952. Less than 1% survived from the 

 1st to the 2nd yr in most areas. The northern Gulf of Maine is near the 

 northern limit of distribution of hard clam; survival to juvenile stages is 

 sometimes very high, but mortality may be catastrophic before commercial size. 

 Predators also flourished with the favorable temps that gave strong hard clam 

 year classes. The possibility exists for transplantation to more favorable 

 areas for rearing to market size. Shellfish growing areas of more than 

 70,000 acres are closed by pollution in Maine. Many are among the most 

 promising biologically for aquaculture and later conditioning in clean water. 

 It is estimated that with aquaculture a crop worth $500 million at the 

 producer level could be grown by 1980, and $2 billion by 1990. An editor's 

 note states that the first article, in the issue of the previous month, 

 listed research projects bearing on aquaculture potentials in Maine. He 

 notes that estimates are maxima, but that, even allowing for losses, farming 

 techniques could improve over wild production. - J.L.M. 



494 



Dow, R. L. 1972. 



Fluctuations in Gulf of Maine sea temperature and specific molluscan 

 abundance. J. Cons. Internatl. Explor. Mer 34(3): 532-534. 



Relict hard clam, Mevaenavia mercenaria, populations survive in anomalous 

 warm-water pockets of the northern Gulf of Maine. Extensive soft clam 

 populations occupy the same shallow coves and many other areas too cold 

 for hard clam reproduction and survival. Abundance peaks of the 2 species 

 frequently coincide in geographical location but not in time. Prehistoric 

 kitchen middens adjacent to a major growing area contain 4 alternate strata 

 of hard and soft clam shells, indicating a cyclic and complementary 

 abundance relationship. In the period 1939 to 1970 landings of soft and 

 hard clam meats in Maine varied inversely. Peaks of soft clam production 

 coincided with periods of relatively low sea temp; the peak of hard clam 

 production came at a time of relatively high water temps. Inventories of 

 standing stocks of clams supported the working assumption that landings 

 were a reliable index of abundance during the period of observation. 

 Predation by green crabs also was a factor in determining abundance. 

 Between historic minimum and maximum sea temp limits the extremely unstable 

 hard clam stocks have varied about 18,000:1 in abundance. - J.L.M. 



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