FISHES OF THE GULF OF MAINE 



429 



On the other hand, none have been reported 

 alive off the Atlantic coast below lat. 37°29' N., a 

 few miles north, that is, of the mouth of Chesa- 

 peake Bay, which makes it likely that the tilefish 

 of southern Florida and of the Gulf of Mexico are 

 isolated populations. 



The onshore-offshore range of the tilefish off our 

 northern coasts, being limited in depth (p. 427), 

 is confined to a bottom belt only some 15 to 25 

 miles wide — astonishingly narrow for so large a 

 fish and one that is so plentiful. And presumably 

 it is a year-round resident wherever it is found 

 there, for its presence has been established north- 

 ward to the offing of southern New England as 

 early in the season as March, and as late as 

 January, while there was no general falling off 

 in the catches in autumn and early winter during 

 the only year (1917-1918) for which monthly 

 data are available. 



Though the tilefish has been reported only once 

 well within the limits of our Gulf, its history and 

 its relationship to hydrographic factors are so 

 interesting that it deserves more attention than 

 its status as a Gulf of Maine fish would warrant 

 otherwise. 



It is astonishing that the very existence of so 

 large a fish so close to our coast should have 

 remained unsuspected until May 1879, when 

 Captain Kirby, cod fishing in 150 fathoms of 

 water south of Nantucket Shoals Lightship, 

 caught the first specimens. Others were caught 

 at 87 fathoms nearby by the schooner Clara T. 

 Friend (Capt. William Dempsey) during the fol- 

 lowing July. And trips by the United States Fish 

 Commission during the next two summers proved 

 that the tilefish were plentiful enough to support 

 an important new fishery. These early investi- 

 gations likewise proved that it occupies a very 

 definite environment, along the upper part of 

 the continental slope and on the outer edge of the 

 shelf where a narrow band of the sea floor is 

 bathed with a belt of warm water (about 47° to 

 53°), varying by only a couple of degrees in tem- 

 perature from season to season, and that it never 

 ventures into the lower temperatures on the 

 shoaling bottom nearer land, nor downward into 

 the icy Atlantic abyss. The balance, in fact, 

 between the physiological nature of the tilefish 

 and its surroundings is so delicate that catastrophe 

 overtook it within three years of its discovery. 

 The first news of this disaster came in March 



1882; throughout that month and the next vessel 

 after vessel reported multitudes of dead tilefish 

 floating on the surface throughout the entire zone 

 inhabited by it north of Delaware Bay, and it has 

 been estimated that at least a billion and a half 

 dead tilefish were sighted. 11 



It has generally been believed that this destruc- 

 tion was caused by a temporary flooding of the 

 bottom along the warm zone by abnormally cold 

 water. 12 Consonant with this is the fact that other 

 species of fish suffered too, and dredgings carried 

 on during the following autumn proved that the 

 peculiar invertebrate fauna that had been found in 

 abundance along this warm zone in previous 

 summers had likewise been exterminated. 



The destruction of the tilefish was so nearly 

 complete that fishing trials carried on off southern 

 New England by the Fish Commission later in 

 1882; in 1883; 1884 (when a particularly careful 

 search was made); 1885; 1886; and 1887 did not 

 yield a single fish. But the species was not quite 

 extinct, as the Gram-pus proved by catching 8 of 

 them off Marthas Vineyard in 1892, and 53 in 

 1893. Tilefish were next heard of in 1897 when 

 a fishing schooner caught 30 fish of 6 to 15 pounds, 

 while long-lining for haddock south of Marthas 

 Vineyard. And tilefish had become so numerous 

 again by 1898 that the Grampus caught 363 

 fish, of K to 29 pounds, on three trips of only 1 to 

 3 days' duration each. 



The length of the period which the fish required 

 to reestablish itself after the mortality of 1882, 

 together with the fact that in 1898 the catch 

 included a considerable number of young fish, is 

 evidence that the replenishment of the stock was 

 chiefly the result of local reproduction, though 

 it may have been been recruited to some extent 

 by immigration from the southern part of the 

 range, where destruction may not have been so 

 complete as it was north of Delaware Bay. 



The tilefish was kept in view during the next 17 

 years by occasional trips to the grounds by the 

 Bureau's vessels. We caught 19, for example, 



u Collins (Rept. U. S. Comm. Fish. (1882], 1884, pp. 237-294A) has described 

 the event in detail, as have many subsequent authors. An account will also 

 be found in Economic Circular No. 19 of the U. S. Bureau of Fisheries. 



u No temperatures were taken on the tilefish ground at the season when the 

 mortality occurred; and the bottom water was nearly as warm there by the 

 end of the following August (48°-49°) as it usually is (about 50°-52°). The 

 temperatures taken in this region during the early years of the Bureau of 

 Fisheries are discussed elsewhere (Bigolow, Bull, Mus. Comp. Zool., vol. 69, 

 1915, pp. 238-241.) 



