FISHES OF THE GULF OF MAINE 49 



indeed, as well as about the Isles of Shoals, hook-and-line fishing is often actually 

 prevented during the period of summer plenty unless cockles be used for bait, 

 for dogfish do not take these. When schools of dogfish rush headlong into net 

 or seine, as often happens, they so snarl the twines that disentanglement and re- 

 pair may be the work of days, and it has been estimated that they do no less than 

 $400,000 worth of damage annually to fishing gear and to fish caught by such 

 gear off the Massachusetts coast alone — probably no less along the shores of Maine, 

 so that in the aggregate they are a heavy debit in the economic scale. Rumor 

 has it, even, that packs of dogfish have been known to attack swimmers and liter- 

 ally bite them to pieces, but we can not vouch for this. At one time or another 

 they prey on practically all species of Gulf of Maine fish smaller than themselves, 

 and squid are also a regular article of diet whenever they are found. Dogfish 

 are also known to take worms, shrimps, prawns, and crabs, and when they first 

 arrive at Woods Hole from the south in May they are often found full of 

 Ctenophores, being one of the few fish that eat these watery organisms. It would 

 be pure guesswork to attempt to estimate the actual numerical strength of the 

 dogfish, but they must be plentiful, indeed, when they can often be caught as fast 

 as they can be hauled in, when line trawls with 1,500 hooks have brought in a 

 dogfish on nearly every hook, and when as many as 20,000 have been recorded in 

 a single draught of a seine in British waters. 



Breeding habits. — -From time immemorial fishermen have known that the spiny 

 dogfish is viviparous. Aristotle, indeed, describes its manner of bearing young. 

 The eggs are large, well stored with yolk, and during early stages of develop- 

 ment those in each oviduct (the so-called "uterus") are contained in a horny 

 capsule that later breaks down, leaving the embryos lying free in the 

 "uterus" with which they have no placental attachment. Ford's studies, men- 

 tioned above, suggest about 10 to 11 months as the period from fertilization 

 to birth, which takes place when the young are 9 to 12 inches (23 to 31 cm.) long, 

 and as they are then practically of adult form with the yolk almost wholly ab- 

 sorbed, strong and active, their chance of survival is excellent. Ordinarily a female 

 has 3 or 4 young to a litter — sometimes as few as 1 or as many as 8 to 11 — and 

 while the embryos are developing in the uteri a fresh set of ovarian eggs is growing, 

 ready to take their place. It has often been suggested that the dogfish may give 

 birth to 2 or 3 litters — -that is, upwards of 20 pups — annually, but if Ford's estimate 

 of the duration of gestation is correct one litter per year would be the rule. State- 

 ments as to the season at which the young are born are conflicting. At Plymouth, 

 England, this takes place from January until March, according to Garstang; from 

 August until December, according to Ford. This, of course, suggests two dis- 

 tinct breeding seasons, and we believe that, similarly, among the dogfish that visit 

 the Gulf of Maine some females give birth to their young in late autumn, others 

 in late winter or early spring. For the evidence on which we base this view we 

 are indebted to Dr. H. V. Neal, whose acquaintance with dogfish on the Maine 

 coast is very intimate. It has long been known that when the dogs first appear 

 on the Massachusetts coast in May or June many of the females contain embryos 



