How to Tell the Sex of a Shark

Ever wondered how to tell the sex of a shark? Distinguishing the sex of a shark is easier than in most marine species. It's all in the shark's external anatomy.

Male sharks have modified pelvic fins called claspers. Females do not have these claspers. As male sharks age, the calcium is deposited in the claspers, so that older males have harder claspers.

In addition to the absence of claspers, females tend to be larger than males, although those differences may not always be obvious, especially in the wild.

Where Claspers Are Located

These claspers are located on the shark's underside, within the shark's two pelvic fins. They look kind of like long fingers that extend underneath the shark's belly. 

Shark Reproduction in Brief

The claspers are used for reproduction. Sharks breed via sexual reproduction with internal fertilization. This involves the sharks usually positioning themselves belly to belly, a process that can involve a lot of biting. The claspers have grooves which are used to transfer sperm from the male shark to the female's cloaca. The sperm is moved through the grooves using seawater. The sperm fertilizes the female's eggs, and voila!—a shark embryo is created. From there, development and birth vary by species. 

In some species, such as bamboo sharks, the female lays eggs outside of her body (oviparous). About 40% of the 400 shark species lay eggs. In ovoviviparous sharks, such as whale sharks, basking sharks, and thresher sharks, the eggs develop inside the female's body, but the young are born live. Placental viviparous sharks give birth in a way similar to mammals—the young shark is nourished inside the female by a yolk-sac placenta, before being born live. Bull sharks, lemon sharks, and hammerhead sharks are examples of species that employ this strategy.