Male and female sandbar sharks only interact during mating; otherwise the sexes swim in separate schools. To initiate mating, male sandbar sharks follow and bite the dorsal fins of females until they flip over. Once flipped over, the male inserts one clasper into the cloaca. Sandbar sharks are considered polygynandrous, meaning females will reproduce with multiple males.
Mating System: polygynandrous (promiscuous)
Sandbar sharks mate in the warm months of the year and females only give birth every 2 to 3 years. The gestation period for sandbar sharks ranges between 9 and 12 months and they may give birth to litters ranging from 1 to 14 pups. The gestation period, litter size, and time of the year when pups are born vary depending on geographic location. Males reach sexual maturity at 160 to 165 cm total length or when claspers are fully developed and have reached the proper hardness. Female sharks reach sexual maturity at 165 to 170 cm total length. Sex differentiation research has shown that levels of steroid hormones may be responsible for development of gonads and secondary sex organs. When near birth, females will enter nursery grounds. At birth, pups range in length from 56 to 75 cm, but some sources have found pups as small as 40 cm. Pup size may be related to mother size, environment, and litter size. Sandbar sharks are the slowest growing and latest maturing of all sharks.
Breeding interval: Sandbar sharks breed every 2 to 3 years, usually in the warmer months.
Breeding season: Mating occurs in warm months; months vary due to geographic location.
Range number of offspring: 1 to 14.
Average number of offspring: 5-12.
Range gestation period: 9 to 12 months.
Average time to independence: 0 minutes.
Average age at sexual or reproductive maturity (female): 7.5 - 8.2 years.
Average age at sexual or reproductive maturity (male): 8.2 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
There is little information regarding any parental investment of sandbar sharks after birth. However, females invest heavily in protecting the young during their development before birth.
Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
- 2009. "International Union for Conservation of Nature and Natural Resources" (On-line). The IUCN Red List of Threatened Species - Carcharhinus Plumbeus. Accessed February 03, 2010 at http://www.iucnredlist.org/apps/redlist/details/3853/0.
- Compagno, L., M. Dando, S. Fowler. 2005. Sharks of the World. Princeton: Princeton University Press.
- Joung, S., C. Chen. 1995. Reproduction in the Sandbar Shark, Carcharhinus plumbeus, in the Waters off Northeastern Taiwan. Copeia, 3: 659-665.
- Joung, S., Y. Liao, C. Chen. 2004. Age and Growth of Sandbar Shark, Carcharhinus plumbeus, in Northeastern Taiwan Waters. Fisheries Research, 70/1: 83-96.
- Portnoy, D., A. Piercy, J. Musick, G. Burgess, J. Graves. 2007. Genetic polyandry and sexual conflict in the sandbar Shark, Carcharhinus plumbeus, in the western North Atlantic and Gulf of Mexico. Molecular Ecology, 16: 187-197.