FISHES OF THE GULF OF MAINE 33 



Occurrence in the Gulf of Maine. — The most northerly locality on the east coast of 

 the United States where the thresher can he called fairly abundant is off Block 

 Island, where, say Nichols and Murphy, 23 it is the commonest large shark, appear- 

 ing in May, most plentiful in June, and remaining until late in the fall. At Woods 

 Hole, too, it has occasionally been taken in the fish traps from April until late in 

 the autumn. Specimens as large as 20 feet in length have been caught there — 

 three fish of 16 feet each in one trap in a single morning. Although only two 

 specimens have been reported at Nantucket, the thresher evidently enters the 

 Gulf of Maine more often than do most of its tropical relatives (e. g., the blue 

 shark) for it has been recorded repeatedly on the coasts of Maine and Massa- 

 chusetts — at Provincetown, Massachusetts Bay, Boston Harbor, Nahant, off 

 Monhegan, east of Matinicus, off Penobscot Bay where a specimen estimated to 

 weigh 500 pounds was caught in 1911, and off Eastport. It is said to have been 

 taken — even to have been common — in the past in the Bay of Fundy, though there 

 is no recent record of it there, and it has been reported entangled in nets off the 

 Nova Scotian coast and even from the Gulf of St. Lawrence. To these records 

 we can add that of several large threshers seen leaping near the Grampus as she 

 sailed through Pollock Rip on August 4, 1913. In fact, next to the mackerel 

 sharks (p. 35) the thresher is no doubt the commonest large pelagic shark in the 

 Gulf. No doubt it also occurs in the mackerel season on Georges and Browns 

 Banks, though we find no definite record of it there. The thresher is to be expected 

 in our waters only in the spring, summer, and autumn; in the cold season it alto- 

 gether deserts the northern coasts for warmer seas. 



Food and hahits. — The tale that the thresher leagues w T ith the swordfish to attack 

 whales is time honored, but it seems that it must be relegated to the category of 

 myth, for few, if any, experienced whalemen can be found to credit it (except in 

 yarns spun to entertain and awe landlubbers!), and so weak toothed is this shark 

 that the second part of the story — that it makes a meal on its huge victim — is an 

 impossibility. In actual fact the thresher feeds chiefly, if not exclusively, on such 

 schooling fishes as mackerel, menhaden, herring (of which it destroys great numbers) , 

 and, in European waters, pilchard. A pair of threshers often work in concert " herd- 

 ing" a school of fish, and it is to frighten its prey together that its enormously long, 

 flail-like tail is employed. Allen 21 gives an interesting eyewitness account of a 

 thresher pursuing and striking a single small fish with its tail. It is, we may add, 

 perfectly harmless to human beings. 



Commercial importance. — In the Gulf of Maine the thresher is not common 

 enough to be of any importance to fishermen one way or another, or to play a 

 practical role of any moment among the smaller fish. Further south, however, and 

 wherever it is numerous in the Atlantic, it makes itself a great pest, tangling and 

 tearing mackerel nets as well as destroying and chasing away the more valuable 

 fishes on which it feeds. 



13 Brooklyn Museum Science Bulletin, vol. 3, No. 1, 1916, pp. 1-34, pis. 1-3. Brooklyn. 

 11 Science, New Series, Vol. LVIII, No. 1489, July, 1923, pp. 31-32. 



