Conservation Comment: Monsters of the Deep

Carcharocles megalodon tooth. Photo / Supplied

This week, Kaupapa Moana - Seaweek will be celebrated all around Aotearoa New Zealand.

This annual celebration is focused on our relationship with the ocean and all marine life. All kinds of activities along the coastline are organised, encouraging participants to enhance and protect our marine environment.

Most New Zealanders live within a few hours' drive of the sea. Many of us have spent happy hours pottering around shorelines, investigating rockpools, dabbling in shallow water, playing in waves and fishing.

Despite its beauty and attractions, the sea can be treacherous. One of the dangers lurking beneath the waves are the apex predators, sharks. A recent very narrow escape from great white shark, which lunged at a surfer off Matakana Island, is a scary reminder that humans can easily be mistaken for the favourite seal meal of great whites.

Bay of Plenty locals report a noticeable increase in the numbers of these sharks in their area. Bronze whalers, mako and blue sharks are often spotted during summer, but great whites were formerly a rare sight.

If the species Carcharocles megalodon, star of the recent movie The Meg, still existed, swimming in the ocean would be unthinkable. The megalodon, which lived millions of years ago in the Miocene period, went extinct when the oceans cooled.

"The Meg" is estimated to have been larger and more deadly than a T-Rex, although it's hard to be sure, as the only part of a shark that is hard enough to fossilise are the teeth, some of which are almost 20cm long.

Despite the occasional shark attack, it is actually sharks that are in great danger from people.

Cruel and unsustainable fishing practices include live-finning, where a captured shark has its fin cut off to sell at a high price for shark-fin soup, then the maimed and bleeding animal is thrown back into the ocean to die. As a result of overfishing and environmental degradation, many sharks, including the majority of hammerhead species, are now critically endangered.

Hammerhead sharks are amazing. Their hammer-shaped heads, with protruding eyes enables them to have 360-degree vision, useful for hunting out their favourite meal of stingray, as well as other fish.

Most of the time, hammer-head sharks congregate in large schools, especially when seeking a mate and when migrating to cooler waters for breeding. Hunting is for nighttime. Solitary and deadly. They will even eat each other, given the chance.

The solitary nature of the hunting hammerhead inspires a popular Māori kowhaiwhai pattern used for decorating wharenui. The mangopare, or hammer-head shark pattern signifies strength, determination, fighting spirit and a strong will.

However, there's no great need to fear the hammerhead if you go for a daytime swim in the ocean. There are a few records of unprovoked attacks on humans, but not of deaths.

The hammer-head's mouth is not as large as the deadly great white, and it is not going to swallow you whole like the extinct megalodon could have. It will save that for a tasty stingray, on a solitary night-time hunt.

Margie Beautrais is the educator at Whanganui Regional Museum