626 



BULLETIN OF THE BUREAU OF FISHERIES 



animals) remaining the year round on the shoals may experience a difference of 11° 

 to 12° with the change of the seasons. 



The bottom temperatm-e usually has ranged from 9° to 10° in about the same 

 depth of water off Mount Desert Island in August, but in the cold summer of 1923 

 it was probably about 2° colder there, judging from a temperature of 7.5° at the 

 30-meter level a few miles farther out from shore on August 5 (p. 599). On Platts 

 Bank the bottom water had warmed only to about 6° at a depth of 71 meters by 

 September 3, in 1925, with 4.5° at 80 meters on the 20th of July (p. 1012); but I 

 may anticipate by pointing out that the temperature there does not reach its maxi- 

 mum for the year until October or even later at depths so great. 



ANNUAL VARIATIONS IN SUMMER TEMPERATURE 



Although the temperature of the gulf shows wide fluctuations with the change 

 of the seasons, our data for seven summers, together with earlier records (p. 514), 

 prove that as a rule there is little difference at a given locality, from year to year, for 

 a given month. However, the period of obsei'vation has included the notably cold 

 summers of 1916 and 1923; such also was that of 1882. Conversely, it is to be 

 expected that unusually warm summers do also occur from time to time, though no 

 definite record of such has yet been obtained in the temperature of the gulf. 



On the whole, the bottom of the western side of the gulf had virtually the same 

 temperature in July and August of 1872 (Verrill, 1874 and 1875) as when deep read- 

 ings were first taken there'' in these same months of 1912. Verrill's readings for the 

 northeast comer of the gulf were consistently 0.5° to 1.5° colder in 1873 and 

 1874 than in 1912, but correspond very closely with the state of that region in 1913. 

 The surface values for 1873 likewise correspond as closely with those for 1912 as 

 could be expected, except that autumnal cooling seems to have commenced earlier in 

 the season in the latter year (Bigelow, 1914, p. 92). 



The summer of 1882 (the year that saw the oft-quoted destruction of the tilefish) 

 was colder than normal in the southern parts of the Gulf of Maine, where the FisJt, 

 Hawk (Verrill, 1882 and 1884, p. 654; Tanner, 1884b) obtained the following readings, 

 with reliable reversing thermometers, on bottom to the eastward of Cape Cod: 



Turning now to the more recent records, we find the August temperatures for 

 1912, 1913, 1914, and 1923 differing so little, one from another, at any level that 

 they may be taken as typical for that month. 



The slight differences between the first three of these years have been discussed 

 in earher reports (Bigelow, 1915, p. 246; 1917, .p. 231). Briefly, the eastern part 



"These early readings and the allowance that must be made for the inaccuracies inherent in the type of thermometer used 

 are discussed in detail in an earlier report (Bigelow, 1914, p. 921. 



