perhaps the strongest evidence supporting the re- 

 ported age determination studies. 



LENGTH-WEIGHT RELATION 



As with many fishes, female spiny dogfish grow 

 longer and heavier than the males. Templeman 

 (1944) reported that the immature females are 

 slightly heavier than the males at all sizes. Mature 

 and pregnant females are significantly heavier 

 than either mature males or immature females. 

 He presents a length-weight graph and lists the 

 following lengtlis and average weights for dogfish 

 from the Newfoundland area: 



Pugsley (1939) reported that Pacific dogfish 

 females tend to be heavier per unit of length than 

 males. He includes a length- weight graph that 

 shows this relation for males, females, and preg- 

 nant females. 



Some length-weight data were collected from 

 210 dogfish at Point Judith, R.I., as part of a study 

 of the Southern New England industrial fishery. 

 These data (sexes combined) were used to calculate 

 the length-weight relation presented in table 3. 



Table 3. — Length-weight relation for spiny dogfish, sexes 

 combined, Point Judith, R.I., October 1965 



POPULATION STATUS 



The total population of the spiny dogfish is not 

 known, although there is no doubt that it is rela- 

 tively abundant and may be subject to long-term 

 Hurt nations in abundance. In the spring of 1846 

 they were so numerous around Gay Head, Mass., 



that 600 were caught on hooks in 1 day by the crew 

 of a single boat (Storer, 1867). 



Collins (1884) relates an eyewitness report from 

 a fisherman who observed a school of mackerel at 

 the surface of Wood Island, Maine, that was being 

 harried by an immense school of dogfish in August 

 1880. The fisherman estimated there were about 

 "100 barrels of dogfish" in the school. The dogfish 

 surrounded the mackerel ". . . in such a manner 

 as to inclose the mackerel on all sides and under- 

 neath, completely preventing their escape." 

 Many of the mackerel were seen with their tails 

 bitten off and with wounds in their flanks. 



Cod as well as mackerel suffered from the at- 

 tacks of the dogfish. Earll (1880) considered the 

 dogfish to be the principal enemy of the cod and 

 reported that adult cod in the market were seen to 

 have teeth marks and spine wounds in their flesh, 

 a result of attacks by dogfish. "The arrival of a 

 school of dogfish in any locality," Earll noted, "is 

 the signal for all other species to leave; and in this 

 way the work of the fisherman is often suddenly 

 terminated." 



Bowers (1906) reported good groundfishing in 

 Boston Bay in July and August 1903, but in 1904 

 ". . . horned dogfish [were] present in such great 

 numbers that it was impossible to catch anything 

 else." 



Dogfish were much more numerous in Massa- 

 chusetts Bay during the last quarter of the 19th 

 Century and during the early 1900's than they had 

 been previously, although in the Woods Hole re- 

 gion they were more plentiful before 1887 than 

 they have been at any time since (Bigelow and 

 Schroeder, 1953). These authors felt that per- 

 haps the period 1904-05 marked a peak in the cycle 

 of dogfish abundance. 



It may be, however, that the population of dog- 

 fish does not fluctuate greatly but that in their sea- 

 sonal migrations the main body of fish may visit 

 one area this year and other areas next year. Our 

 lack of knowledge about the nature of the popula- 

 tion (s) makes it difficult to come to any firm con- 

 clusion regarding the absolute or relative numbers 

 of fish involved. 



As a result of his early studies of the dogfish 

 around Newfoundland, Templeman (1944) said, 

 "It is obvious . . . that dogfish migrate rapidly 

 and for long distances, and since they swim chiefly 

 in the upper layers of water there are no hinder- 



538 



U.S. FISH AND WILDLIFE SERVICE 



