Reproduction of the sandbar shark, Carcharhinus plumbeus, in the Northwest Atlantic and Gulf of Mexico
Mature female sandbar shark ovary. Image © Florida Program for Shark Research
Recent stock assessments of the Sandbar shark have shown their population levels are severely depressed. Updated data on the reproduction of the C. plumbeus
is currently needed. This study is focused on determining the reproductive cycle of both male and female sandbar sharks. Specimens for this study have been collected through fishery-dependent and -independent bottom long-line fishing since 2003. Sandbar shark reproductive tracts have been dissected in the field and preserved in formalin for analysis in the lab. Morphological measurements of the testes, epididymides, seminal vesicles, ovaries, nidamental glands, and uteri have been taken for approximately 800 specimens. Further, histological preparations of reproductive tissues have been used for additional analysis on a subset of samples. Preliminary results indicated a distinct seasonal trend in reproductive activity. Uterine content data suggest a gestation period of 12 months. Ovulation and parturition occurs in late June and early July. Peak mating activity appears to occur during the month of June. Ovarian oocyte data suggest a protracted female reproductive cycle that merits further analysis. The reproductive data gathered in this study will be used to update stock assessment models to better conserve this overly exploited species.
Reproduction of the great (Sphyrna mokarran) and scalloped (S. lewini) hammerhead sharks
Uterus of a scalloped hammerhead shark. Image © Florida Program for Shark Research
To date, no study has examined the reproduction of the scalloped hammerhead shark in U.S. waters or the great hammerhead shark in any habitat. Accurate reproductive knowledge of these sharks is paramount for effective fisheries management. We are analyzing reproductive tracts of male and female hammerhead sharks caught both in fishery-dependent and -independent long-line fishing. To date we have analyzed 140 hammerhead shark reproductive tracts. Analysis of the gonad size, accessory sex organs and uterine continents will allow us to determine the size of maturity and the timing of reproductive events. Data from our previous and ongoing age and growth studies will allow us to determine the age of maturity. The results from this study will be used to develop better stock assessment models for these sharks.