LIFE HISTORY OF THE SPINY DOGFISH 



By Albert C. Jensen, Fishery Biologist (Research)' 

 U.S. Bureau of Commercial Fisheries Biological Laboratory, Woods Hole, Mass. 



ABSTRACT 



The spiny dogfish, a small shark, is a costly nuisance 

 to commercial fishermen off both coasts of the United 

 States. Data on the species' life history were gathered 

 from the literature and from original studies and 

 assembled in one report as a basis for possible future 

 management. The species reaches a maximum length 

 of 100-124 cm. and a maximum weight of 7-10 kg. 

 The females are slightly larger than the males. Dogfish 

 are known to migrate in large schools and, occasionally, 

 to travel long distances. Tagging studies suggest they 

 move offshore in the winter and inshore in the summer. 

 They are opportunistic feeders with a diet list that 

 includes fishes and crustaceans. Age determinations 

 from interpretation of spine markings indicate the 

 dogfish are long lived with some individuals living for 



20 or 30 years. The species Is ovoviviparous and mating 

 takes place in the cold months. After a nearly 2-year 

 gestation period, a female gives birth to 3-11 pups, each 

 about 25 cm. long. Natural mortality rate apparently 

 is low, and the species has few natural enemies. In 

 1944 more than 40 million pounds of spiny dogfish were 

 landed as a source of vitamin A. Today about 2 million 

 pounds are landed. In the United States the species 

 has limited value as an industrial fish and even less value 

 as a food fish. It is edible, however, and is valued as 

 food in some European nations. Management of the 

 spiny dogfish off North America is indicated to reduce 

 the damage it causes to more valuable commercial 

 fisheries. 



The spiny dogfish Squalus acanthi as L., a small 

 shark of the family Squalidae, has been one of the 

 most intensively studied fishes, but one in which 

 extensive knowledge is lacking. The species is 

 studied by college students in zoology, ichthyology, 

 comparative anatomy, and vertebrate taxonomy 

 and is a favorite experimental animal for physio- 

 logical studies including pharmacological toxicity 

 tests. Few T comprehensive biological studies of 

 this fish have been made, however, except for 

 Ford's (1921) study at Plymouth, England, Tem- 

 pleman's (1944) study in Newfoundland, and the 

 studies made by Bonham, Sanford, Clegg, and 

 Bucher (1949) in the State of Washington. In 

 general, most of the published reports represent 

 isolated observations or extremely specific studies. 

 As a result, we know, for example, the function 

 of the rectal gland of the spiny dogfish (Burger 



1 Present address: Institute of Marine Science, University of Miami, Fla. 

 Note. — Approved for publication February 9, 1965. 



and Hess, 1960), but we do not know the winter- 

 ing grounds of the species ; we know the mechanism 

 controlling movements of the spiral intestine 

 ( Sawyer, 1933 ) , but we do not know the relation- 

 ship between the groups of dogfish in any one area. 



This paper is an attempt to organize and sum- 

 marize the available information, to which I have 

 added additional original data from recent studies 

 of the spiny dogfish in the Northwest Atlantic. 

 This report is undoubtedly incomplete, brat will 

 serve as a starting point for other studies and help 

 the researcher who is not completely familiar with 

 the literature to interpret future observations. 



As a convenient method of handling the infor- 

 mation, the various phases of the life history of 

 the fish are taken up in turn. Because the species 

 is distributed throughout the Northern Hemi- 

 sphere (Bigelow and Schroeder, 1948), I have 

 reviewed reports from both the Atlantic and Pa- 

 cific Oceans. Some consideration has been given, 



FISHERY BULLETIN! VOLUME 65, NO. 3 



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