Smith and Abramson: Leopard shark tag-recovery data from San Francisco Bay 



375 



Progeny as a function of maternal age was then esti- 

 mated by applying the weight-length-age relationships 

 cited above. We assume all nondeformed embryos sur- 

 vive to time of birth. Data were not available for ap- 

 plying the preferable procedure of directly regressing 

 fecundity on age. 



Geographical names and location of the tagged-fish 

 release area are given in Figure 1. 



Results 



Tagging 



A total of 948 sharks were tagged off Hunters Point, 

 San Francisco, in south San Francisco Bay between 

 26 July and 13 September 1979. Most were tagged in 

 August (68%) and September (26%). The hook rate was 

 very high: 22 Triakis per 100 hooks, and a 44% hook 

 rate for all elasmobranchs. Other sharks and rays taken 

 in order of abundance were brown smoothhound Mus- 

 telus henlei (n = 872), bat ray Myliobatis califomica 

 (n=159), soupfin shark Galeorhinus galens («. = 6), 

 sevengill shark Notorhynchus cepedianus {n = 5), and 

 spiny dogfish Squalus acanthias (n = 2). 



The lengths of tagged leopard sharks ranged from 

 51 to 144 cm TL (mean 81 cm, Fig. 2). The male:female 

 ratio was 53:47. Large individuals may have been 

 underrepresented in the tagging, since only 9% of 

 females and 11% of males were over 100 cm. Commer- 

 cial fishermen have reported a higher proportion of 

 large fish in their catches, fishing at the same time with 

 similar gear but in different areas of the south bay (B. 

 Van Gorp and B. Fraser, commercial shark fishermen, 

 pers. commun., June 1980). On the other hand, leopard 

 sharks were probably recruited to our gear at a larger 

 size than would be true for typical sportfishing tackle. 

 Anglers fishing from shore and piers using small hooks 

 would surely take a higher percentage of fish under 70 

 cm than that shown in Figure 2. 



Of the 948 fish tagged, 82 individuals were classified 

 as "injured" and the remaining 866 fish as "healthy." 

 Return rates would presumably be higher for healthy, 

 uninjured fish than for injured fish if the tagging opera- 

 tion caused mortalities; the absence of such a difference 

 could be taken as suggestive of little or no tagging- 

 induced mortality (Gulland 1983). 



Recoveries 



As of 30 September 1988, 108 fish had been recaptured 

 of which 101 had known recapture date and location. 

 A breakdown of all methods of recapture is given in 

 Table 3, and provides an interesting glimpse of the 

 various users of the leopard shark resource. The pro- 



TRIAKIS - SEXES COMBINED 



m 



u 



to 



■H-i 



rfl-. 



80 30 100 110 120 130 140 150 

 TUTAl LENGTH (CMi 



Figure 2 



Length frequency of tagged leopard sharks (sexes combined) released 

 off Hunter's Point in south San Francisco Bay, California, 1979. 



portions reported by each group should approximate 

 the proportions of the natural population harvested or 

 caught by each group. 



