University of South Alabama Ichthyological Col- 

 lection (USAIC 6278). Measurements and 

 weights are found in Table 1. 



Since most records of C. isodon are of juveniles, 

 there is little information on the reproductive 

 biology of the species. Based on the cited litera- 

 ture and these data, pups appear to be 45-55 cm 

 at birth. However, seasonality is uncertain as the 

 records of Springer (1950) are not in accord with 

 those of either Hoese and Moore (1977) or this 

 report. 



Length at maturity can be closely estimated. 

 One male (112 cm) collected 13 July 1978 was 

 immature — based on incomplete calcification of 

 the claspers and incompletely developed siphon 

 sacs, each sac being 7.5 cm long and 1.0 cm wide. 

 The other two males ( 120 and 127 cm) collected 2 

 July 1979 and 28 June 1978 had well-calcified 

 claspers and fully developed siphon sacs. The only 

 literature on mature males (Springer 1950) listed 

 lengths of 140-152 cm. Males apparently mature 

 between 115 and 120 cm. Maturity in females 

 must be reached at a larger size. The female col- 

 lected in July 1979 was 127 cm, yet was imma- 

 ture with only small undeveloped ovarian eggs. 

 The gravid female reported here was 139 cm, and 

 those reported by Springer (1950) were 147-155 

 cm. 



Carcharhinus isodon was only collected when 

 similarly sized specimens of blacktip shark, C. 

 limbatus, were caught: 3 C. limbatus ( 126-166 cm) 

 with the gravid female, 12 C limbatus (102-117 

 cm) with the 112 cm male, 2 C limbatus (111 and 

 124 cm) with the 127 cm male, and 12 C. limbatus 

 (100-130 cm) with the two specimens caught in 

 1979. If C. isodon is an uncommon straggler into 

 the northern Gulf of Mexico it may be schooling 

 with other sharks of like size. Sharks that school 

 have been noted to do so by sex or size (Ford 1921). 



Literature Cited 



Bass, a. J., J. D. D' Aubrey, and N. kistnasamy. 



1973. Sharks of the east coast of Southern Africa. I. The 

 genus Carcharhinus (Carcharhinidae). Oceanogr. Res. 

 Inst. (Durban), Invest. Rep. 33, 168 p. 

 BIGELOW, H. B., AND W. C. SCHROEDER. 



1948. Sharks. In Fishes of the western North Atlantic. 

 Part one, p. 59-546. Mem. Sears Found. Mar. Res., Yale 

 Univ. 1. 

 Burton, E. M. 



1940. Aprionodon isodon from South Carolina. Copeia 

 1940:140. 



Clark, E., and K. Von Schmidt. 



1965. Sharks of the central Gulf Coast of Florida. Bull. 

 Mar. Sci. 15:13-83. 



COMPAGNO, L. J. V. 



1978. Sharks. In W. Fischer (editor), FAO species iden- 

 tification sheets for fishery purposes: western central At- 

 lantic. Vol. 5, unpaginated. 



Dahlberg, M. C, and R. W. Heard, III. 



1969. Observations on elasmobranchs from Georgia. Q. 

 J. Fla. Acad. Sci. 32:21-25. 

 FORD, E. 



192 1 . A contribution to our knowledge of the life-histories 

 of the dogfishes landed at Plymouth. J. Mar. Biol. As- 

 soc. U.K. 12:468-505. 



Gilbert, P. W., and D. A. Schlernitzauer. 



1966. The placenta and gravid uterus of Carcharhinus 

 falciformis. Copeia 1966:451-457. 



Hoese, H. D., and r. H. Moore. 



1977. Fishes of the Gulf of Mexico, Texas, Louisiana, and 

 adjacent waters. Tex. A&M Univ. Press, College Sta- 

 tion, 327 p. 

 Radcliffe, L. 



1916. The sharks and rays of Beaufort, North Caroli- 

 na. Bull. U.S. Bur. Fish. 34:239-284. 



Springer, S. 



1950. A revision of North American sharks allied to the 

 genus Carcharhinus. Am. Mus. Novit. 1451, 13 p. 



Steven Branstetter 



ROBERT L. SHIPP 



University of South Alabama 

 Dauphin Island Sea Lab 

 P.O. Box 386 

 Dauphin Island, AL 36528 



SHEDDING RATES OF PLASTIC AND 



METAL DART TAGS FROM ATLANTIC 



BLUEFIN TUNA, THUNNUS THYNMUS^ 



In 1971, the International Commission for the 

 Conservation of Atlantic Tunas (ICCAT) recom- 

 mended that a double-tagging experiment be con- 

 ducted on Atlantic bluefin tuna, Thunnus thyn- 

 nus, to determine whether plastic or metal dart 

 tags were more efficient and to estimate im- 

 mediate and instantaneous tag shedding rates. A 

 knowledge of shedding rates is necessary so that 

 appropriate adjustments can be made when es- 

 timating mortality rates from tag return data. 

 This study was begun in 1971 by the National 

 Marine Fisheries Service (NMFS), the Woods Hole 

 Oceanographic Institution (WHOI), and the 

 Fisheries Research Board of Canada (FRBC). The 



^Southeast Fisheries Center Contribution Number 80-14M. 

 FISHERY BULLETIN: VOL. 78, NO. 1, 1980. 179 



