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Fishery Bulletin 100(4) 



60-80 cm total length (TLl (54-72 cm fork length |FL]) 

 (Shann, 1923; Compagno 1984, Francis and Stevens, 2000). 

 Bigelow and Schroeder (1948) speculated that females are 

 gi-avid by 152 cm TL (136 cm FL), whereas Aasen (1963) 

 concluded that females mature between 200 and 250 cm TL 

 (193-240 FL) and males mature between 150 and 200 cm 

 TL (146-193 FL). In a more comprehensive study, Francis 

 and Stevens (2000) found that females mature between 165 

 and 180 cm FL in the South Pacific. 



In this study, we present the results of a comprehensive 

 examination of porbeagle reproduction in the NW Atlantic 

 Ocean. We define the sizes and stages of maturity for both 

 sexes and provide insights into the reproductive cycle, as 

 well as embryo sex ratios and litter sizes. These parameters 

 will be useful for the refinement of fishery management 

 plans for the porbeagle shark in the NW Atlantic Ocean. 



Materials and methods 



Porbeagles were collected with pelagic longline onboard 

 both U.S. and Canadian commercial fishing vessels and 

 U.S. research vessels fishing in U.S. and Canadian waters 

 from the Gulf of Maine and Georges Bank ( northeastern 

 U.S.) to the Grand Banks off southern Newfoundland. Sev- 

 eral specimens were obtained at a sport-fishing tourna- 

 ment held on Stellwagen Bank, Massachusetts. Sampling 

 took place between 1979 and 1999, but most of the data 

 were obtained during 1993, 1994, and 1999. 



Morphometries 



For each shark, five lengths were measured over the curve 

 of the body to the nearest half centimeter (cm): interdor- 

 sal length (posterior dorsal fin base to origin of second 

 dorsal fin; IDL); dorsal length (origin of first dorsal fin to 

 precaudal pit; DL); precaudal length (snout to precaudal 

 pit; PCD; fork length (snout to fork of tail; FL); and total 

 length (snout to a perpendicular line from the tip of the 

 upper caudal fin in a natural position; TL). Total length 

 of embryos were measured along a straight line with the 

 tip of the tail fully extended (TL,) because of the difficulty 

 in obtaining over-the-body or FL measurements (or both) 

 in embryos less than 6 cm TL. FL and PCL were taken 

 when possible. FL are reported for all sharks in our study; 

 TL values are presented for embryos with calculated or 

 measured FL in parentheses. TL can be converted to FL by 

 using the following regression (Campana et al.^): 



TLj can be converted to FL for embryos by using the 

 regression 



FL = 0.832(rL )-0.19 



FL=0.885(rL)-i-0.99 



[/•-=0.99,;!=361]. 



All other length and weight conversions can be found in 

 Campana et al.' Aasen's ( 1963) TL values were converted 

 to FL by using the approximate formula: 



FL = 0.947*(Aast'nrL) + 3.64 (Campana^). 



[7-2=0.99, ?! = 131] 



^ Campana, S.E. 2000. Unpubl. data. Department of Fisher- 

 ies and Oceans, Bedford Institute of Oceanography, P.O. Box 

 1006, Dartmouth. Nova Scotia, Canada, B2Y 4A2. 



Whole weight in kilograms (kg) was taken when possible. 

 Literature values of TL were converted to FL for compari- 

 son and the conversions are presented throughout the text 

 in parentheses. The converted values from the literature 

 should be considered good estimates only because of the 

 variation in measurement techniques between studies. 



Maturity Indicators 



A number of measurements, weights, and conditions were 

 taken on reproductive organs in both sexes to develop indi- 

 ces of maturity following Pratt (1979, 1993, 1996). Most 

 specimens were measured fresh; however, some frozen 

 reproductive tracts were also measured. Reproductive 

 tracts were measured on the right side of the specimen. 

 Organ terminology follows Pratt (1979) (Fig. 1, A and B). 



For more detail, uteri were divided visually into anterior 

 and posterior segments. The anterior segment is defined 

 as the portion between the origin of the uterus at the 

 isthmus and the point where both uteri join. The posterior 

 segment is the portion from the junction to the posterior 

 constriction of the uterus (Fig. IB). A length measurement 

 was taken for the anterior uterus, and width was taken 

 midway along this portion of the uterus. 



Active ovulation was defined as occurring if 1) ova were 

 entering the ostium or were present inside the upper 

 oviduct, 2) ova and capsules were present in the oviducal 

 gland, 3) encapsulated ova were present in the isthmus, 

 and 4) encapsulated ova were present in the uterus. 



Prior mating activity was assessed according to the pres- 

 ence or absence of a vaginal membrane (hymen), deter- 

 mined by passing a probe through the posterior end of the 

 uterus into the cloaca. The presence of vaginal mating scars 

 was used to determine if recent mating had taken place. 

 Scars were identified as either healed or recent. Maturity 

 status of both sexes was assigned to each shark based on 

 all reproductive organ characteristics (Pratt, 1979). The 

 size at SO'/r maturity was determined by fitting a logistic 

 regression to a plot of percent maturity versus FL. 



Embryos were either frozen or preserved in 10% buff- 

 ered formalin. Litter size and embryo sex were deter- 

 mined in the field or in the laboratory under a dissecting 

 microscope. Embryo growth was related to month. Linear 

 regressions were fitted to the relationship between mean 

 embryo length and month for samples from the NW At- 

 lantic and southwest Pacific Oceans and compared with 

 analysis of covariance (ANCOVA). 



Results 



Male length at maturity 



Reproductive data were obtained from 393 male porbeagle 

 sharks ranging in size from 86 to 246 cm FL, of which 



