Fishes of the Western North Atlantic 117 



size from about 45 mm. in length (in one of 180 mm., Fig. 17) to about 235 mm. (in one 

 of 400 mm.") or to more than half the total length. The throat region of the embryo too 

 is enormously expanded, giving it a most grotesque appearance. Also, the caudal fin is at 

 first much more asymmetrical than in the adult, assuming the lunate form with growth 

 of the embryo, and the young are very large at birth, witness embryos of 19, 24 and 18 

 inches in a five- foot female.^^ A Gulf of Maine female of 10 feet contained a 20-pound 

 embryo.^' Corresponding to the large size of the embryo, gravid females normally contain 

 only one to four young (0-2 per oviduct), although five have been reported." 



Habits. This has been described repeatedly as an active, strong-swimming species 

 when in pursuit of its prey. When hooked, however, it puts up only a very feeble resist- 

 ance, as we have experienced. We have never seen or heard of one jumping in its attempt 

 to escape, as the Mako does (p. 128). Nor is there any difficulty in landing specimens of 

 four to five feet on an ordinary hand-line j in fact, it is as proverbial for its sluggishness 

 under such circumstances as is the Mako for its activity. 



Mackerel Sharks are often seen finning at the surface on calm days; on the other 

 hand, many have been caught on bottom with cod and halibut lines as well as at mid-depths 

 now and then in drift nets in northern European waters, while one is occasionally entangled 

 in a mackerel net. Evidently, then, their depth range is from the surface down to bottom; 

 on the cod fishing grounds that would be to some 70 to 80 fathoms at least; it is not known 

 how much deeper they descend. 



In the waters of northern Europe gravid females have been taken from localities so 

 widely scattered as to show that the species produces young throughout its East Atlantic 

 range. Presumably this is true in the western Atlantic also, although embryos have actually 

 been recorded only from the vicinity of Monhegan Island, Maine, in August, from off 

 Portland, Maine, in November and in January (see p. 119) and from Barnstable, Massa- 

 chusetts, in October (see Study Material, p. 112). In Europe, females with embryos 

 have been reported for the winter months as well as for summer. But the fact that the 

 largest embryos have been found in summer indicates the latter as the chief season of 

 production. 



Lamna nasus preys largely on schools of mackerel, herring and (in the eastern At- 

 lantic) pilchards; also on such ground fish as cod, hake, cusk, and other gadoids, flounders, 

 or any other fish that may be available, and on squid. In the eastern Atlantic its diet also 

 includes whiting (Gadus merlangus), spiny dogfish {Squalus acanthias) and John dory 

 {Zeus jaber). It also has the troublesome custom of foraging on cod, etc., that have been 

 hooked on long lines, biting off the snoods in the process. 



Relation to Man. During the first quarter of the last century the liver oil of this 

 species, mixed with other fish oils, was in considerable demand (chiefly for tanning pur- 



11. Nordgard, K. norske Vidensk-Selsk. Skr. Trondh. (1923— 1924), 1925: 38, fig. 22. 



12. Shann, Rep. Fish. Bd. Scot., 1911: 73, pi. 9. 13. Hubbs, Copeia, 123, 1923: loi. 



14. Lijbbert and Ehrenbaum, Handb. Seefisch. Nordeurop., j, 1936: 278. A shark with 10 embryos reported long 

 ago as this species (Wilder, Science, /, 1880: 236) probably was some other. 



