Rare giant ocean wanderer has secrets to tell
Scientists are preparing to bring a rare sharp-tailed sunfish out of the big chill, with hopes it will shed new knowledge on the elusive ocean-dwelling species. Matt Stewart reports.
THEY have been described as the ‘‘tropical vagabonds’’ of the sea and now one of them is living, or rather thawing, at Te Papa. The 2.1-metre, 230kg sharp-tailed sunfish will come out of the deep freeze on Tuesday and give scientists a rare opportunity to study its anatomy and feeding habits.
Te Papa sciences collection manager Andrew Stewart says it is a prime specimen of the rarest known species of sunfish.
‘‘Usually they turn up like a thick, leathery suitcase with nothing inside but with this one we know all the internal organs are intact. This is very, very rare and it’ll probably cause quite a stir internationally,’’ Mr Stewart says.
The sunfish, gender unknown, is now being held at the national museum’s autopsy room in Tory St, Wellington.
Tomorrow the thawing process begins. For scientists, the acquisition of this well-preserved specimen is a huge opportunity to add to the scant knowledge of these rarely spotted giants, which roam the ocean from the equator to the Tasman Sea and halfway to South America.
This particular sharp-tail was first spotted in the shallows at Omaha Beach, north of Auckland. Beachgoers, boaties and surfers tried to nudge it back into the open ocean but the massive fish beached itself and died.
Auckland Museum fish expert Tom Trnski was alerted and, having ‘‘dropped everything’’, was at the beach within an hour. ‘‘I wasn’t initially that interested but as soon as I saw the photos I realised how important it was,’’ Dr Trnski says.
When he arrived, rescuers had already put a tarp over the fish, preventing seagulls from eating the corpse. With the help of about eight people, it was loaded on to a trailer and sent to Auckland.
However, the fish proved too big for Auckland Museum and so was instead sent south to Te Papa.
The Omaha specimen is just the second sharp-tail recovered in New Zealand waters for use by museums. The first was a less complete carcass found off Wairarapa in 1981, which is also held by Te Papa.
A live sharp-tailed sunfish was also captured and released in June in Northland.
‘‘Sharp-tailed sunfish are very rare in collections and very little is known of their biology,’’ Dr Trnski says.
Because of their size, sunfish are mostly left to themselves, although they can draw unwanted attention from bigger predators, including killer whales, tooth whales and large sharks.
‘‘By the time you’re that big very few animals want to take you on,’’ Mr Stewart says.
The Omaha specimen has no obvious battle scars so it remains a mystery how it died, at least until it thaws.
‘‘We’re really keen to deter- mine the cause of death because there’s no external marks and it was quite sick when it washed up.’’
To begin the big thaw, the sunfish will be hosed and kept damp with a cloth.
Scientists will then open its gut to uncover more about its diet. After it is weighed, measured, dissected, biopsied and its gender is determined it will be put in a formalin solution to kill bacteria.
After three months it will be transferred to a 1600-litre steel tank.
But while sunfish are rare in New Zealand waters for now, this may be changing. Mr Stewart says more of these ‘‘tropical vagabonds’’ could beach on our shores if the pattern of hot summers and mild winters continues.
Te Papa is still deciding if the Omaha specimen will go on public display. At the very least, a video of scientists carrying out research will be exhibited.