SHARKS 25 



which is found in most subtropical and temperate seas, being 

 especially abundant in the Mediterranean and Atlantic. A 

 Japanese writer has recently described two forms to be found 

 in the seas around Formosa, distinguished principally by 

 differences in the shape of the caudal fin, the size of the eye, 

 and the proportions of the tail and body, but it seems possible 

 that these are only varieties of the same species, the one with 

 the larger eye inhabiting deeper water or even living near the 

 sea bottom, and the one with the smaller eye living at the 

 surface. The Thresher is one of the commonest of the larger 

 sharks found on the British coasts. 



This is a rather formidable looKing shark, although quite 

 harmless to man. It is a great nuisance to fishermen, as it not 

 only destroys their catches, but also becomes entangled in 

 their nets with disastrous results. It is a speedy surface 

 swimmer, feeding almost exclusively upon fishes, especially 

 herring, shad, pilchard and mackerel. In obtaining a meal 

 the Thresher sometimes makes use of a curious and unique 

 method, swimming round and round a shoal of fish in ever- 

 decreasing circles, lashing the water with its tail, and thus 

 driving the prospective victims into a compact mass, when they 

 form a comparatively easy prey. Sometimes a pair of sharks 

 will combine in carrying out this organized method of feeding. 

 Mr. Coles has described one which was feeding in shallow water 

 on the coast of Carolina, which was " throwing the fish to its 

 mouth with its tail, and . . . one fish, which it failed to 

 seize, was thrown for a considerable distance, clear of trie 

 water ". A Thresher taken in the trawl in the Firth of Forth 

 had half a bushel of garfish in its stomach — a good example 

 of its voracious appetite ! Stories of Threshers attacking 

 whales in league with swordfishes are probably without founda- 

 tion, and may be due to faulty observation, the shark being 

 confused with the Killer Whale. Its mouth and teeth are both 

 far too feeble for the achievements in this direction that have 

 been ascribed to it. 



The breeding habits of the Thresher are unknown, but the 

 young are believed to be born during the summer. 



It is of practically no economic value, although the Chinese 

 and Japanese make some use of it. Dr. Day reports that the 

 Greek fishermen are said to have sought the Thresher for food, 



