We came across this dead juvenile Smooth Hammerhead shark (Syphyrna zygaena) at St Helier’s beach, Auckland, New Zealand on New Year’s Day. I was intrigued about it. They are such unusual looking creatures. There was a large gash in one side just behind the gills so I suspect perhaps it was a foul hooked or a propeller injury that was the cause of death but I can’t be sure. Te Ara: The Encyclopedia of New Zealand has this to say about them
“The distinctive skull of the hammerhead shark (Sphyrna zygaena) is believed to help detect prey, and to add lift like a hydrofoil, counteracting the downward push of the tail. Hammerheads are olive to dark grey, with a white underbelly, and grow to 4 metres. Large individuals can be dangerous to people.
Known in Māori as kakere or mangōpare, hammerheads are regular summer visitors to North Island waters, venturing as far south as Cook Strait. Juveniles as small as half a metre are sometimes seen in the Hauraki Gulf – it is possible that the species gives birth around New Zealand. They are found worldwide in temperate and tropical waters, from the coast to continental shelves.”
Unfortunately there doesn’t seem to be very much more information about these bizarre looking creatures. A quick literature search revealed lots of studies of their abundance and distribution along with other shark fauna. For example they make up 1% of the shark species caught by long line tuna fishing on the West coast of India and 5% around the Andaman and Nicobar Islands (John & Varghese 2009). In a study of sharks caught in nets protecting swimming beaches in KwaZulu-Natal, South Africa they had a low probability of being entangled in plastic or having ingested plastic compared to some other shark species (Cliff et al 2002). However this doesn’t necessarily tell us they are better at avoiding plastic – they might just be less likely to get caught in nets if they’re badly effected by plastic.
The oldest study I was able to find (there are possibly older ones to be found with more searching) was published in 1907 and is well worth reading (Gudger 1907). It’s a great short story. I love the detail and the modest amount of feeling which is all but impossible with today’s word limits and specifications on scientific papers.
If you know more about this shark or study them then please comment or provide a link to more information.