south or inshore-offshore migration pattern (Jen- 

 sen, 1961). In these experiments, 155 dogfish 

 were tagged near Cape Ann, Mass., in July 1956, 

 and 50 were tagged on Browns Bank in October 

 1957. To date, nine tags have been returned 

 (5.8 percent), eight from the 1956 experiment and 

 one from the 1957 experiment. Most of the tag- 

 ged fish were recaptured relatively close to the 

 areas in which they had been released; six were 

 caught less than 50 miles from the tagging area; 

 one, 73 miles away ; and another, 140 miles away. 

 One, however, at liberty nearly 5 years, was re- 

 captured 200 miles away, on the eastern edge of 

 Georges Bank. In general, the recaptures suggest 

 that spiny dogfish return to the same general area 

 at about the same time of year and the same fish 

 probably school together for long periods of time. 



An interesting recapture was made recently of 

 a dogfish tagged in a later series of experiments 

 carried out aboard the Delaware. The fish was 

 1 of 143 caught on handlines in 18 m. of water, 

 July 22, 1961. It was tagged and released 3 miles 

 off Halibut Point, Cape Ann, Mass., and was re- 

 captured by a commercial otter trawler in 119 m. 

 on December 30, 1961, in the vicinity of the Hud- 

 son Canyon. The fish had moved about 250 miles 

 in 23 weeks and was caught south and offshore of 

 the tagging area. This recovery adds further 

 evidence to support the hypothesis that some of 

 the dogfish that spend the summer in the inner 

 Gulf of Maine migrate south and offshore to spend 

 the winter. 



Table 2 gives the tagging and recapture in- 

 formation for 17 spiny dogfish tagged by person- 

 nel of the Bureau of Commercial Fisheries Bio- 

 logical Laboratory at Woods Hole. The 17 re- 

 present the returns from a total of 844 dogfish 

 tagged in 1956, 1957, 1960, and 1961. 



SEROLOGICAL STUDIES 



An approach to the identification of spiny dog- 

 lisli subpopulations, by blood typing techniques, 

 was made by Sindermann and Mairs (1961). The 

 authors proposed a two-antigen blood group sys- 

 tem. They found that individual dogfish collected 

 in the Gulf of Maine were of blood types Si, S 2 , 

 S,S 2 , or S . Blood groups of pregnant females 

 and their unborn pups were compatible, "... 

 with a simple genetic hypothesis of three alleles, 

 S 1 , S'-'. :uid S°, controlling the system." Continua- 



tion of the work, complemented with tagging and 

 other population studies, will make it possible to 

 determine the existence of reproductively isolated 

 subpopulations of spiny dogfish. In addition sero- 

 logical techniques may clarify the relationship be- 

 tween the various Squakis species and groups 

 throughout the world. 



FOOD HABITS 



Several studies of the stomach contents of spiny 

 dogfish from many parts of the Northern Hemi- 

 sphere have shown that it is primarily a fish eater 

 but will also feed on invertebrates, both swimming 

 and bottom-dwelling forms. In many areas, clu- 

 peoids are important in the diet of the dogfish, but 

 it undoubtedly feeds on whatever species it can 

 capture. 



In the Pacific Ocean three important studies of 

 dogfish feeding habits have been made. One such 



534 



U.S. FISH AND WILDLIFE SERVICE 



