between hard clam landings and water temp in the same year should be taken 

 as evidence of a temp effect. Several years elapse between birth and 

 attainment of commercial size, and this time lag could be expected to be 

 at a maximum in the cold waters of the Gulf of Maine. Regardless of this 

 fact, however, correlation analysis per se cannot prove cause and effect, 

 although the method has been used at times, especially by fishery biologists, 

 to draw conclusions about environmental effects. Often results are obtained 

 by repeated trials, using different combinations of data, and this in- 

 validates conclusions about statistical significance. This paper does not 

 state that the results reported were obtained by trial and error, but the 

 results reported in the tables lead one to suspect that this was done. 

 Correlation coefficients are reported for data matched for the same year, as 

 for hard clam and other species, and for pairs of data lagged by as much as 

 8 yrs . For most species, the rationale by which data were matched is not 

 stated. The importance of temp in determining success of spawning and other 

 biological variables at the northern limit of the species range is so well 

 known that it is not necessary to draw on a questionable technique like 

 correlation analysis to "prove" it.) - J.L.M. 



498 



Dow, Robert L. 19 78. 



Size-selective mortalities of clams in an oil spill site. Mar. Pollution 

 Bull. 9(2): 45-48. 



Mixed no. 2 fuel oil and JP5 jet fuel from an oil spill in Long Cove, 

 Searsport, Maine became concentrated locally at levels up to over 250 ppm in 

 intertidal sediments 15 to 25 cm beiow the surface. The spill was in 

 March 1971, and oil continued to kill successive annual sets of Mya arenaria 

 as they burrowed through overlying clean sediments into the oil concentration 

 beneath. Nearly all dead clams were faster growing and larger than those 

 that had survived for a longer time. Juvenile clams setting on the clean, 

 redistributed surface sediments survived through 3 or more growing seasons. 

 As they grew, they burrowed more deeply until they finally reached heavier oil 

 concentrations. (Abstracter's note: Mercenaria mercenaria apparently was not 

 involved. It could be assumed that, because quahogs do not dig as deeply, 

 they might have been less affected.) - J.L.M. 



499 



Dow, Robert L. (no date - probably early 1970s) . 



Maine law affecting marine resources. Chapter 12 in Problems Influencing 

 Use of Renewable Marine Resources. Partial report under a study carried 

 out under the joint sponsorship of: The School of Law of the University of 

 Maine and the National Science Foundation Office of Sea Grant Programs , p. 

 743-787. 



Prior to World War II shellfish were looked upon as a standby food for hard 

 times, a food not in keeping with American culture and affluence. In Maine 

 the resource was considered primarily the property of all residents, and 

 not as a resource to be exploited commercially. All that has changed, 

 although traditions linger. For the most part management has not been 

 based on scientific facts. Some kitchen middens have alternating layers of 

 soft and hard clams, suggesting that the two species may alternate in 

 abundance reciprocally. Temperature is suggested as the cause, based on 

 recent observations that appear to show that hard clams thrive at higher 

 water temperatures than soft clams. Optimum sea surface temperature for 

 hard clam is 50.2°F., for soft clam 46.1°F. At extremes of temperature 

 hard clam populations have fluctuated of the order of 18,000 to 1. In one 

 3-acre area (Brighams Cove) over a 10-year period yield of hard clams per 

 acre per year was 6,600 lbs. In warm years, when hard clam production 

 rises, conditions are apt to be optimum for two major predators also, 

 green crab, Caveinus maenas , and rock crab, Canaer irroratus . Survival of 

 the hard clam year class of 19 52 was greatly reduced by crab predation and 

 winter mortality. Hard clams were reared in hatcheries in 1951 and 1952. 

 Recently, artificially reared juveniles were planted in growing areas, pro- 

 tected from predation by fences. To prevent freezing juveniles should be 

 planted in subtidal waters. Hard clam aquaculture should be feasible in 

 Maine. - J.L.M. 



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