CLIMATE AND THE DISTRIBUTION OF MARINE ANIMALS 



339 



season is progressively higher from the siiore sea- 

 ward all around tiie Gulf, not only at any given 

 level but downward over the bottom as well, it is 

 safe to say that in no winter since 1948 has any 

 animal living as deep as 20 to 40 meters (whether 

 on tlie bottom or in the mid-depths) anywhere in 

 the Gulf been in danger of chilling if resistant to 

 temperatures as low as 34° to 35° F., while any 

 animal resistant to 38° to 40° has been safe at 

 100 meters anywhere in the open basin of the 

 Gulf. A majority of the members of the fauna, 

 whether bottom-dwelling or free-swimming, living 

 along the middle Atlantic coast and shelf at these 

 depths are no doubt as hardy as this or they would 

 not maintain permanent populations there. 



Consequently, there is nothing apparent in win- 

 ter temperatures such as may be assumed to have 

 prevailed in the Gulf during the last 5 years or so 

 to hinder the free interchange in shoal water of 

 animal populations of the Gulf of Maine and of 

 the coastal belt along southerly New England, 

 Xew York, and perhaps Xew Jersey. This is in 

 line with Parr's findings (1933, p. 87), based on a 

 great number of temperatures taken at lighthouses 

 and lightships, 1928 to 1930, that in winter the 

 shallow belt along the mid-Atlantic coast was 

 "equally in open continuity with the waters north 

 of Cape Cod." This despite the fact that the 

 mean temperature of the coldest month of the 

 year at Boston was 3° to 4° lower during the 

 period covered by Parr's observations (32.9°-33.6° 

 F.) than during the past 5 years, 1948-52 (35.9°- 

 37.6°). 



Notwithstanding this continuity of conditions 

 and the increase in winter temperatures, the quali- 

 tative composition of the fish fauna is not uniform 

 from north to south around Cape Cod in winter. 

 We find, for example, that of some 30 species re- 

 ported in the commercial landings in the New 

 York-New Jersey area in January and February, 

 1952-54, only 8 are found north of Cape Cod in 

 winter and they are permanent residents. Of the 

 7 leading species in these landings, only 1, the 

 whiting {MeiiuccivM hilinearis) is reported in com- 

 mercial lancHngs north of Cape Cod in winter. On 

 the other hand, 4 of these 7 species are common 

 north of the Cape in summer and the other 3 have 

 been reported north of the Cape at one time or 

 another. Tliere is, then, little evidence that the 

 increase in winter temperatures has altered the 

 general distributional pattern of the fisli fauna in 



the Gulf, with the possible exception of the whiting 

 which has appeared in the commercial catches in 

 winter only in recent j^ears (p. 329). 



On the other hand, we do not know of any ani- 

 mal native to the Gulf, even among the cold- 

 season spa\v^lers, that requires a temperature lower 

 than 34° to 36° or so, either for its successful re- 

 production or for any other stage in its life his- 

 tory. Winter temperatures higher now than 

 formerly can thus be classed as an improvement, 

 from the faunistic standpoint, except perhaps for 

 accidental strays from more-northerly seas that 

 might reach the Gulf more often during colder 

 periods, and might survive longer there, for 

 instance, the Greenland shark and the capelin. 



Since it is not possible to deteimine whether 

 some whiting have always wintered in the deeper 

 parts of the Gulf, we cannot say that any marine 

 animal formerly not found north of the Cape in 

 winter has become a year-round resident under 

 category 1 (p. 338). Sea temperatures and the 

 commercial-landing data (p. 329), however, indi- 

 cate that the whiting falls within category 4, since 

 it appears safe to assume that this fish has always 

 been a permanent resident of the Gulf. 



Evidence, too varied for analysis here, makes it 

 likely that the spread of some animal populations 

 from the south and west past Cape Cod toward 

 the north and east into the Gulf of Maine is 

 bounded more effectively by the distribution of 

 temperature during the warmer part of the year 

 than by regional differences in the degree to which 

 the coastal waters chill in winter. Since the great 

 majority of the adult animals of our middle At- 

 lantic seaboard can survive in water that is as 

 cool as the western side of the Gulf in summer, if 

 not as cool as the nortlieastern side, the critical 

 need here is for water warm enough for normal 

 numbers to reproduce successfully. The oyster, 

 surviving in a temperature close to the freezing 

 point for a considerable period but requiring a 

 temperature of 68° F. or higher for spawning, 

 illustrates this category; the quahaug, or hard 

 clam {Venus mercenaria), spawns successfully 

 only in a temperature of about 68° to 70° but 

 winters successfully where the water chills to 

 34° to 35°. 



Despite tlic liiglicr temperatures that have pre- 

 vailed of late, tlie fauna of the Gulf — shoal water 

 as well as deep — is composed today of much tlie 

 same assemblage of species of fisli and of inverte- 



