PLANKTON OF THE GULF OF MAINE 



325 



and early May of 1920, and at all four of the stations on the continental slope. The 

 localities for the gulf proper (fig. 90) are all from the deepest trough, as is the one 

 autumn record for the eastern basin just mentioned, and most of the captures have 

 been in hauls from considerable depths, as follows: 



The single September specimen was from a tow at 130-0 meters, while the June 

 specimens off southern Nova Scotia (station 10295) were from 500-0 meters. The 

 reader will note that there are only two records (a total of two specimens) from tows 

 shoaler than 100 meters, one of which was taken over much deeper water and may 

 have been brought up from its normal habitat by some local upwelling; the other was 

 on Georges Bank. 



Associated with the considerable depth of the records, we have usually found 

 S. maxima in water of the relatively high salinity of 33.5 to 34 per mille, or more, 

 though on the rare occasions when it is swirled up toward the surface it may stray 

 into less saline strata of water (32.36 per mille at station 20081 ; 32.6 per mille on 

 Georges Bank). Its general distribution farther north, and especially its failure to 

 colonize the Gulf of St. Lawrence (Huntsman, 1919), suggests that it is unable to 

 survive in water of low salinity, irrespective of temperature. 



S. maxima is at home only in comparatively low temperatures. We have never 

 found it in temperatures warmer than about 6.5° within the gulf, but, on the other 

 hand, it usually lies below the coldest level in waters of 3.5 to 5°, the only records from 

 temperatures lower than 3° being its sporadic appearances in the upper levels, in about 

 1.63° at station 200S1 and about 2.6° at station 20066. The captures of S. maxima 

 along the continental slope have been in temperatures of 3 to 6° and salinities of 

 34 to 34.9 per mille. It occurred under about these same conditions over the con- 

 tinental shelf abreast of Shelburne in March, 1920 (stations 20074 and 20076). 

 Occasionally, however (whether or not as a result of upwelling is not clear) , we have 

 taken it in decidedly warmer water at our outermost stations ; for example, in 7 to 8° 

 temperature at station 20129 and one specimen in 9° or warmer at station 20044. 



In north European seas S. maxima is equally characteristic of cold but highly 

 saline water layers (Apstein, 1911), and probably it is this rather precise relationship 

 to the physical state of the water which bars it from the Gulf of Maine in summer but 

 allows it access there in winter; for while the trough of the gulf is sufficiently salt for 

 it throughout the year and cold enough — say, 5° to 6° below 100 meters — in winter and 

 early spring, the bottom water may well be too warm for it in some summers if not in 

 all. At such times any maxima that drift inward through the eastern channel 



