How do sharks reproduce?

Oviparous sharks deposit tough collagenous egg cases, sometimes called mermaid’s purses. Tendrils or ridges can anchor a case to reef, algae or seafloor. The embryo develops outside the mother using yolk, and incubation can last many months. Finding an empty case on a beach reveals a reproductive strategy, not necessarily a dead baby shark.

In lecithotrophic viviparity, embryos are retained in the uterus and rely mainly on yolk before live birth. Other species supplement that supply through uterine secretions, a yolk-sac placenta or additional unfertilized eggs. Lamnid sharks such as makos and white sharks practice oophagy, in which developing embryos consume eggs produced by the mother.

Older sources often use “ovoviviparous” for eggs that hatch inside the mother. Modern reproductive biology separates the mechanisms more precisely because maternal provisioning matters. Two species that both give birth to live pups may have very different placental anatomy, gestation length and energetic costs.

Many large sharks grow slowly, mature late and produce small litters at long intervals. Those traits work in stable ecosystems with naturally high adult survival, but they make populations vulnerable when fishing removes mature animals faster than they can be replaced. Conservation plans therefore need species-specific life histories, not a generic “fish reproduce quickly” assumption.