495 



Dow, Robert L. 19 73. 



Fluctuations in marine species abundance during climatic cycles. Mar. 

 Tech. Soc. J. 7(4): 38-42. 



Hard clam abundance is directly related to sea temperature. Three major 

 year classes (1937, 1947, 1952) have occurred in Casco Bay, Maine. In 

 those years mean annual surface water temperatures were 9.0°, 9.2°, and 

 10.1°C. Growth and survival to commercial size depend on favorable 

 temperatures. Continued high temperature in the mid-1950s led to high 

 mortalities, from crab predation. Records of hard clam catches in Maine 

 do not exist prior to 1931. Since that time greatest catches of hard 

 clam have coincided with high mean annual water temperatures. Since 

 1939 the minimum has been 6.4°C in 1939, the maximum 11.1°C in 1953. 

 (Abstracter's note: A correlation between two such sets of data does 

 not necessarily prove cause and effect. The data presented for clam 

 catches are for the same year as the mean annual temperatures. If the 

 correlation has meaning, this would mean a direct kill of adult clams, 

 or that temperature functions in some way to make clams of legal size 

 less available to diggers. It could not be a temperature effect on 

 spawning or on eggs, larvae, and young. The table in which temp and clam 

 data are given contains information also on production of oysters (3 yrs 

 later), lobsters (same yr) , 3-yr-old bloodworms, 3-yr-old sandworms, 

 scallops (6 yrs later) , soft clams (5 yrs later), and shrimp (4 yrs later) . 

 Aside from the statistical questionability of the correlation method of 

 establishing cause and effect, this evidence of data manipulation makes 

 the conclusions questionable.) - J.L.M. 



496 



Dow, Robert L. 19 75. 



Reduced growth and survival of clams transplanted to an oil spill site. 

 Mar. Poll. Bull. 6(8): 124-125. 



Experiments were conducted with My a arenavia. Mevcenav-La mercenaria is not 

 mentioned. - J.L.M. 



497 



Dow, Robert L. 1977. 



Effects of climatic cycles on the relative abundance and availability of 

 commercial marine and estuarine species. J. Cons. Internatl. Explor. Mer 

 37(3): 274-280. 



The northern Gulf of Maine, normally the habitat of boreal species, is 

 intruded by vertebrates from the south in periods of relatively high sea 

 temp, in sufficient numbers to support commercial fisheries. Abrupt and 

 spectacular changes also occur in abundance of resident warm-water 

 invertebrates, including Meraenaria mevcenavia. Relationships between 

 sea surface temp and landings of various commercial species in Maine were 

 examined by simple linear correlation. Cause and effect were inferred. 

 Except for the anomalous Gulf of St. Lawrence, the Gulf of Maine is the 

 northern limit of the range of hard clam. The species is relatively 

 abundant only when water temp is high enough to permit successful spawning 

 and survival of progeny. In cold periods a nucleus of survivors, mostly 

 old clams, continues in deeper waters. Some may be 25 yrs old or more, 

 and intervals between commercially important survival of progeny may 

 exceed 20 yrs. Hard clam was exhausted commercially in the area by 1937, 

 when the first of 3 important year classes (1937, 1947, 1952) resupplied 

 the fishery and extended the life of the fishery to 1962. Recently, an 

 increase in annual mean water temp to 9.4°C has led to modest recovery of 

 the stock and resumption of harvesting. From 1939 to 1962 inclusive a 

 positive correlation of 0.80 (r 0> oi= - 52 ) was found between hard clam 

 landings and annual mean water temp in the same year. Similar correlations, 

 some positive, some negative, were found for 23 other species. It was 

 concluded that sea temp has been the principal environmental regulator of 

 species abundance and availability in the Gulf of Maine. (Abstracter's 

 note: it is puzzling that a positive and allegedly significant correlation 



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