144 KENDALL: NEW ENGLAND SALMONS. 



The 'landlocking' process was not synchronous in all lakes inhabited by the fish in 

 recent times, but in general, pari-passu with the changing conditions northward follow- 

 ing the recession of glacial conditions. Probably not all of recent natural salmon lakes 

 were stocked in this way, for there are some localities where it seems that they must 

 have spread by way of inland water routes. 



That the lake salmon were relatively late arrivals in fresh water is indicated by the 

 fact that in some instances chars and smelts occur in waters above waterfalls which are 

 now insurmountable by any fish and where they could not have gained access at any 

 other time than when the falls were not as formidable as at present. But when salmon 

 appear above such falls possible routes of dispersal are evident. 



If the immediately foregoing theory is in accord with the facts, the nearest to a 

 marine prototype of the lake salmon would be those now found in the most northern 

 regions, as for example the White Sea, Iceland, Greenland, and Ungava Bay, if the 

 salmon actually occurs in the latter locaUty. Smitt in 1886 recognized the White Sea 

 salmon as different from the Baltic salmon and gave it the name of Salmo brevipes. 



Of course it is recognized that this hypothesis is mostly speculation, but it must be 

 admitted that many facts warrant it. To repeat: it is manifestly impossible that the 

 fish should have originated in those fresh waters, which they now inhabit, for the region 

 was once covered by a field of ice thousands of feet thick over a period of thousands of 

 years. The fact that Lake salmon now flourish only in certain cold ' glacial lakes', indicate 

 that their present physiological requirements are the culmination of thousands of years 

 of adaptation to changmg conditions since their preglacial progenitors roamed the seas. 



Since the foregoing was written Dr. Henry B. Ward (1932) has advanced a theory of 

 'The origin of the landlocked habit in salmon' in which he regards temperature as the 

 principal factor. His theory is based largely upon his observations on the effect upon 

 sockeye salmon (Oncorhynchus nerka) produced by a dam erected comparatively recently 

 in Baker River at Concrete, Washington. Although most of the evidence in support of 

 his theory pertains to apparent results of a recent restriction of sockeye salmon to the 

 lake produced by the dam, and the waters above it, Ward extends the theory to apply 

 to landlocking of salmon in general. 



Ward's idea of the landlocking process will be made sufficiently clear by a quotation 

 from what he says under the heading 'Origin of a natural race of Landlocked Salmon' 

 (p. 577) and of his conclusions (p. 578-579). He saj's: 'The question now arises — how 

 do conditions in nature resemble those which were artificially created by the erection 

 of the dam, and do somewhat similar influences ever interfere to prevent the young 

 salmon from completing the journey to the sea? Earher in this paper attention was 

 called to the fact that landlocked salmon planted in certain lakes tend to desert those 

 waters. One mil naturally assume that in such cases some influence is lacking which in 

 other locaUties inhibits the fish from deserting the lake. I am of the opinion that tem- 

 perature is the ruling factor and that changes known to have occurred in the recent 

 geological historj^ of the northern hemisphere are calculated to afford an adequate 

 explanation of the formation of landlocked races of salmon in widel}^ scattered lakes.' 



