306 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



250 meters at a station in the southeastern part 

 of the basin in July 1914 and of 46.7° and 47° at 

 190 meters in the northeastern part in August 

 show that the temperature of the slope water 

 moving inward at some intermediate level via the 

 channel between Georges and Browns Banks is 

 often higher than the reading recorded near the 

 bottom. Readings near the bottom have ranged 

 from 42.9° to 45° (average, 44.2°) at 4 stations in 

 March and April 1920, July 1915, and July 1914. 



Table 4. — Mean temperatures recorded in Gulf of Maine at 

 depths of 160 to 330 meters, by season 



(Recorded in 1912-16, 1919-21, 1923, and 1926. Temperatures in °F.] 



Month 



Feb.-Mar. 

 Apr.-May 

 June-July- 

 Aug.-Sept 

 Nov .-Jan. 



Western part of 

 basin 



Mean 

 tempera- 

 ture 



41.2 

 41.8 

 42.0 

 43.1 

 41.4 



Number 



of 

 readings 



Eastern part of 

 basin 



Mean 

 tempera- 

 ture 



41.0 

 41.4 

 45.9 

 43.7 

 44.5 



Number 



of 

 readings 



R 

 7 

 11 

 1 



Since it is the actual temperature with which we 

 are primarily concerned in the present discussion, 

 it is sufficient to add that the 71 readings taken at 

 160 to 330 meters in various parts of the basin, 

 summarized in the preceding table, ranged be- 

 tween 38.4° and 47° F., with 54 of the 64 readings 

 falling between about 40° and 44°. There is 

 nothing in the record to suggest that the tempera- 

 ture of the deep bottom water within the basin of 

 our Gulf has fallen appreciably below these limits, 

 or risen above them, in any year since Gulf tem- 

 peratures have been recorded. 



TREND IN WATER TEMPERATURES BETWEEN 

 1912-26 AND 1953-54 



For the period 1926 to 1953, our most instruc- 

 tive sources of information as to ups and downs of 

 temperature around the shoreline of the Gulf of 

 Maine are the mean montlily temperatures that 

 have been reported by the United States Coast 

 and Geodetic Survey for Boston since 1922 and 

 for Eastport since 1930 (U. S. Coast and Geodetic 

 Survey, 1951; with subsequent data contributed 

 in advance of publication); the mean monthly 

 temperatures for St. Andrews, Now Brunswick, 

 1921 to 1947, tabulated by Hachey and McLcllan 

 (1948, p. 357); and the mean annual temperatures 

 for that same port, 1921 to 1953, published by 



Lauzier (1954, p. 8, fig. 1). Lauzier (1952, p. 6), 

 has already pointed out that "St. Andrews water 

 temperatures reflect general water conditions over 

 a large section of the Atlantic coast" of Canada. 

 On geographic grounds, a shift in either direction 

 at Boston that persists through several years may 

 be expected to prove an equally reliable index to 

 any upward or downward shifts that may have 

 taken place in the western part of the Gulf in 

 general. 



At Boston, the mean temperature for the coldest 

 month of the year did not show any long-term 

 trend, either upward or downward, from 1922 

 through 1936. Wiiile it was higher for the winters 

 of 1029 to 1933 (33°+) than for those of 1922 

 to 1926 (below 32°), it was again lower than 32° 

 in 1934, 1935, and 1936, with means as low as 

 29.8° for 1934 and 1936. But the mean for the 

 coldest month, whicli had averaged 31.7° for the 

 8-year period 1922-29, averaged 33.1° for the 

 period 1930 to 1937, 32.6° for 1938 to 1945, 33.8° 

 for 1946 to 1948, 36.7° for 1949 to 1951, and 36.5° 

 for 1952 to 1954. Furthermore, there has not 

 been a winter since 1944 when the mean water 

 temperature for the coldest month has fallen below 

 32° in Boston Harbor, though this happened in 11 

 of the preceding 21 years. 



Summer air temperatures, also, liave clearly 

 tended upward in Boston Harbor during the past 

 30 years (1922-53), whetlier expressed as the 

 departure from the mean for July-September or 

 as the mean for tlie warmest month for successive 

 4-year periods (table 5). Indeed tliere has not 

 been a summer during the 13-year period 1941-53 

 when the mean temperature for the warmest 

 month was not higher than it was in 8 of the 18 

 years from 1922 to 1940; while there has been only 

 one summer (1948) since 1941 when the mean 

 temperature was not at least as high as 66.6°, a 

 level equalled only 6 times during the 19-year 

 period 1922-40. Similarly, the mean tempera- 

 ture for the 2 warmest months combined, which 

 was not above 65.3° for any 2 consecutive years 

 between 1922 and 1941 (average, 64.1°) has been 

 66.5° or higher (mean, 67.1°) in every subsequent 

 year, with the sole exception of 1948. 



The mean water temperature for the year as a 

 whole also has tended upward at Boston and by 

 about the same amount (table 6). And while 

 mean annual temperature is of little ecological 

 significance in regions wiiere water temperatures 



