727 



Abstract— Reproductive organs from 

 393 male and 382 female porbeagles 

 (Lamna nasus), caught in the western 

 North Atlantic Ocean, were examined 

 to determine size at maturity and 

 reproductive cycle. Males ranged in 

 size from 86 to 246 em fork length 

 (FL) and females ranged from 94 to 

 288 cm FL. Maturity in males was best 

 described by an inflection in the rela- 

 tionship of dasper length to fork length 

 when combined with clasper calcifica- 

 tion. Males matured between 162 and 

 185 cm FL and 50% were mature at 

 174 cm FL. In females, all reproduc- 

 tive organ measurements related to 

 body length showed a strong inflection 

 around the size of maturity. Females 

 matured between 210 and 230 cm FL 

 and 50% were mature at 218 cm FL. 

 After a protracted fall mating period 

 (September-November), females give 

 birth to an average of 4.0 young in 

 spring (April-June). As in other 1am- 

 nids, young are nourished through 

 oophagy. Evidence from this study indi- 

 cated a one-year reproductive cycle and 

 gestation period lasting 8-9 months. 



The reproductive biology of the porbeagle shark 

 (Lamna nasus) in the western North Atlantic Ocean 



Christopher F. Jensen 



North Carolina Department of Environment and Natural Resources 



Division of Marine Fishenes 



PO Box 769 



Morehead City. North Carolina 28557-0769 



E-mail address Caltimuscdta'aol com 



Lisa J. Natanson 



Harold L. Pratt Jr. 



Nancy E. Kohler 



National Marine Fisheries Service, NOAA 



28 Tarzwell Dr 



Narragansett, Rhode Island 02882 



Steven E. Campana 



Marine Fish Division 



Bedford Institute of Oceanography 



PO Box 1006 



Dartmouth, Nova Scotia 



Canada B2Y 4A2 



Manuscript accepted 29 May 2002. 

 Fish. Bull. 100:727-738 (2002). 



The porbeagle {Lamna nasus), a pe- 

 lagic shark in the family Lamnidae, 

 inhabits the cold temperate waters of the 

 North and South Atlantic, South Pacific, 

 and southern Indian Oceans, as well as 

 the subantarctic region of the Southern 

 Ocean (Svetlov, 1978; Compagno, 1984). 

 In the western North (NW) Atlantic 

 Ocean, the porbeagle ranges from the 

 Flemish Cap and the Grand Banks off 

 southern Newfoundland, Canada, to the 

 Gulf of Maine and (rarely) south to New 

 Jersey (Templeman, 1963; Compagno, 

 1984). The porbeagle is most commonly 

 encountered from the Gulf of Maine to 

 the Grand Banks, where it has been the 

 subject of a commercial fishery since 

 1961 (O'Boyle et al.i; Campana et al^^). 

 Seasonal abundance is related to 

 north-south migrations (Aasen, 1963; 

 Campana et al.-^; Aasen''). 



Lamnid sharks are ovoviviparous 

 and nourish their embryos by oophagy 

 (Lohberger, 1910). Early descriptions 

 of porbeagle embryos exhibiting ooph- 

 agy were documented by Swenander 

 (1907) and Shann (1911, 1923), and 

 more recently by Francis and Stevens 

 (2000). Litter size has been variously 

 reported as one to five pups (Dunlop, 



1897; Swenander, 1907; Shann, 1911, 

 1923; Gauld, 1989; Francis and Stevens, 

 2000). Birth size has been reported as 



1 O'Boyle, R. N., G. M. Fowler, P. C. F. Huriey, 

 M. A. Showell, W. T. Stobo, and C. Jones. 

 1996. Observations on porbeagle (Lamna 

 nasus) in the north Atlantic. DFO (De- 

 partment of Fisheries and Oceans) Atl. 

 Fish. Res. Doc. 96/24, 29 p. Marine Fish 

 Division, Bedford Institute of Oceanog- 

 raphy, RO. Box 1006, Dartmouth, Nova 

 Scotia, Canada B2Y 4A2. 



' Campana, S., L. Marks, W. Joyce, P. Hurley, 

 M. Showell, and D.Kulka. 1999. An ana- 

 lytical assessment of the porbeagle shark 

 {Lamna «a.s(/s) population in the Northwest 

 Atlantic. CSAC (Canadian Stock Assessment 

 Secretarate) Res. Doc. 99/158, 57 p. Ma- 

 rine Fish Division. Bedford Institute of 

 Oceanography, P.O. Bo.x 1006, Dartmouth. 

 Nova Scotia, Canada B2Y 4A2 



' Campana, S., W. Joyce, L. Marks, P. Hurley, 

 L. J. Natanson, N. E. Kohler, C.F. Jensen, J. 

 J. Mello, and H. L. Pratt Jr 2000. The 

 rise and fall (again) of the porbeagle shark 

 population in the Northwest Atlantic. 

 Unpubl. manuscr Marine Fish Division. 

 Bedford Institute of Oceanography, P.O. 

 Box 1006, Dartmouth. Nova Scotia, Ca- 

 nada B2Y 4A2 



^ Aasen, O. 1961. Some observations on 

 the biolog)' of the porbeagle shark (Lamna 

 nasus L.i ICES CM. Copenhagen 1961, 

 Near Northern Seas Committee 109:1-7. 



