Shark mothers provide critical life support for newborn pups


The Dusky shark (Carcharchinus obscurus). Image: Dennis King.

Sharks have experienced widespread overfishing in recent decades, with coastal and pelagic species undergoing substantial declines in many areas. Yet much concerning the basic life history of sharks is unknown and successful efforts to rebuild their populations require substantially improved understanding of their reproductive cycles.

Live born shark pups are found in litters ranging from 10-20 individuals that are released from the womb with no post-partum maternal care. The first few weeks of life are critical as they entail the highest risk of mortality and are a time when shark pups must learn to forage for food.

The pups are not without help however; a collaborative team from AIMS, the University of Bangor (Wales), and the Natal Sharks Board (South Africa) analysed 40 years of catch records from shark control nets in South Africa to demonstrate that shark mothers provision their pups with enlarged ‘super livers' that the pups utilize for energy during the first few weeks of life.  The study also revealed that the reproductive output of female sharks peaks below their maximum size, indicating that larger, older sharks are not necessarily the most fecund. This suggests that key size ranges can be targeted for conservation to maximize the reproductive potential of many coastal shark species.