604 ANNUAL REPORT SMITHSONIAlSr INSTITUTION, 1917. 



The Fisheries steamers Albatross and Fisli Rawk, and the 

 schooner Grampus, made a number of trips each year to the former 

 tilefish grounds without taking a single specimen, and in the Report 

 of the National Museum for 1889, the species was listed, provision- 

 ally, as extinct. Professor Verrill made extensive collections along 

 the edge of the Gulf Stream, the habitat of the tilefish, in 1880, 1881 

 and 1882, and in the latter year had occasion to report that " One of 

 the most peculiar facts connected with our dredging this season 

 (1882) was the scarcity or absence of many of the species, especially 

 Crustacea, that were taken in the two previous years, in essentially 

 the same localities and depths, in vast numbei's, several thousand at a 

 time." He was of the opinion that the disaster to the tilefish was 

 accompanied by v/holesale destruction of bottom life, and that the 

 two were due to the same cause, the encroachment of cold waters from 

 inshore on the bottoms formerly bathed by the Gulf Stream. 



In 1889, Prof. William Libbey, in behalf of the United States 

 Fish Commission, undertook an investigation of the physical char- 

 acter of the sea off the south coast of New England. He found 

 that the Gulf Stream was " off soundings," that is, its warm waters 

 did not touch the bottom, but in 1890 and 1891 he found that it was 

 progressively nearer the edge of the continental platform and was 

 able to predict that in 1892 the old tilefish grounds again would be 

 bathed in warm Gulf Stream water, and present a favorable environ- 

 ment for the fish. In July of 1892 the Grainpus proceeded to the 

 locality, set its trawls and caught the fxsh. The explanation of the 

 extraordinary occurrence of March, 1882, appears to be this: 



The tilefish, like the cod, is a bottom dweller ; but, unlike the cod, 

 it is of a family accustomed to the warmer waters of the Tropics. It 

 finds a congenial temperature where the edge of the Gulf Stream 

 touches the sea bottom, on a slope as steep as a mountain side, and 

 there is, therefore, but a narrow strip on which the water is neither 

 too shallow nor too deep. The Gulf Stream is a gi'eat, w^arm, oceanic 

 I'iver flowing between banks of cold water, not fixed like the solid 

 banks of land streams but pushed one way or the other as the path 

 of the stream approaches or recedes from the coast. There is evi- 

 dence that about the time of the decimation of the tilefish the Gulf 

 Stream was receding, and as it moved offshore its warmth no longer 

 reached the bottom and the fish and other animals dwelling there were 

 left in the chilly waters w^hich took its place. It is reasonable to sup- 

 pose that being hal^ituated to a warm and equable submarine climate 

 they were killed by the cold wave which enveloped them. 



When the warm water again touched the bottom the fish migrated 

 from areas in which the mortality had not been so complete. Fur- 

 ther mvestigatious showed that the fish were gradually increasing 



