Vulnerable predators

On the 9^th of September this summer two tiny dead hammerhead sharks were found on the rocky shoreline in Porto da Cruz on Madeira’s North-Eastern coast. The baby sharks were very small and must have died almost right after being born. They have been entangled in blue nylon fishing line and their location above the high tide mark indicated them having been caught by anglers who fish from the shore in the coastal waters in that area. The bodies were more or less well preserved, so they could have not been lying there in the rocks for a long time.

Regarding the form of their frontal head without an indentation in the middle of the snout, the little animals were most likely Smooth hammerheads (Sphyrna zygaena). Those sharks are with a maximum length of up to 4 m the second largest of all hammerheads. Only the Great hammerhead (Sphyrna mokarran) is bigger. The Smooth hammerheads occur in subtropical and temperate oceanic waters around the globe. They prefer coastal regions but can also be found in shelf zones and open seas.

Those sharks are viviparous, a female can give birth to more than 20 pups which are around half a meter in length when they are born. Looking at their sizes, the dead ones found on the shore must have died in a very young age. The nursery areas of Smooth hammerheads consist of shallow coastal waters. They are known to give birth around Madeira.

To see the loss of those two baby sharks is very sad. Smooth hammerheads are classified as “vulnerable” by the IUCN and like all sharks reach their sexual maturity relatively late. In their role as predators, they are absolutely essential for healthy marine ecosystems. The populations are globally declining which is mainly caused by human activities. Habitat degradation, marine pollution, overfishing, food scarcity and bycatch are just some of the reasons. We might check whether the canned tuna was fished in a dolphin friendly way but no one seems to care about the sharks. Something we might think about…

by Jan-Christopher Fischer