Migrations of Spiny Dogfish & Squalus acanthias & and Recapture ...

TEMPLEMAN: Spiny Dogfish Migrations from Tagging51TABLE 3. Number of tagged spiny dogfish recaptured in various areas and months from tagg ing in Newfoundlandwaters in 1963-65.Area of recapture May Jun Jul Aug Sep Oct Nov Dec TotalRecaptures in calendar year of taggingWest Newfoundland 1 2South Newfoundland 42 5 3 5 58East Newfoundland 1 1 2 5Total Nfld region 44 6 5 2 5 2 65Recaptures 1-19 years after tagging yearWest Newfoundland 1 1 9 5 2 4 22South Newfoundland 2 12 44 9 12 7 4 90East Newfoundland 4 2 5 4 15Total Nfld region 3 13 57 16 19 11 8 127 aRecaptures south ofLaurentian Channel 4 4 2 12aIn addition, there was one recapture from Halibut Channel in January.TABLE 4.Monthly recaptures of tagged spiny dogfish by depth, from taggings in Newfoundland watersduring 1963-65. (Depths of recapture were usually reported in fathoms.)Depth(m) Jan May Jun Jul Aug Sep Oct Nov Dec Total0-18 1 3 16 2 1 2419-37 5 44 8 13 1 1 7238-55 2 3 13 5 6 3 4 3656-73 1 1 3 1 2 4 1274-91 1 1 2 3 4 1192-137 1 1 2 5138-183 5 1 1 8184-247 1 3Total 4 13 84 19 22 12 14 2 171during the summer and autumn, with peak returns forJuly (Table 3). There were no returns from the westcoast after October, although 185 dogfish were taggedat Bonne Bay and Lark Harbour in November. On theeast coast, recaptures occurred from July toNovember, implying delayed migration northwardfrom southeastern Newfoundland. There was onerecapture by otter trawl in Halibut Channel south ofNewfoundland in January. No inferences about thetimes of northward and southward migrations of spinydogfish can be made from the recaptures south of theLaurentian Channel in May-September.Recaptures occurred mainly in shallow coastalwaters during the summer and at greater depths duringthe autumn (Table 4), the trend being coincidental withthe cod fishery which peaks in summer at shallowerdepths and declines to a low level in autumn as the codretreat from the coast into deeper water.Growth from tagging and recapture recordsAn 85 cm female spiny dogfish, tagged on 26 May1965 on northwestern St. Pierre Bank, was 94 cm (totallength) when recaptured off S1. Pierre on 27 October1975. Two other reliable growth records for femalespiny dogfish tagged in Newfoundland waters werereported by Templeman (1958, 1975): one fish was 73cm when tagged and 81 cm when recaptured 10 yearslater, and the other was 74 cm when tagged and 87 cmwhen recaptured 11 years later. These growth recordsindicate slower growth than that of female spiny dogfishin the western North Atlantic, based on estimationof ages from dorsal spines (Soldat, 1982).Tag returnsDiscussionThe overall retu rn rate of 9.4% from the spi ny dogfishtaggings reported in this paper compares favorabIywith we st ern At Iantic tag returns of 5.0 %(Templeman, 1954), 3.0% (Jensen, 1969) and 2.5%,omitting returns from the last year of tagging (Shafer,MS 1970), and with eastern Atlantic returns of 8.8%(Holden, 1965) and 10.8% (Aasen, 1964). Apart fromthe Newfoundland records, some of these percentages