Students discover fish's mystery hunting skill

Students discover fish's mystery hunting skill

As far as fieldtrips go, it was a memorable one for Northcote College students who documented a previously unknown airborne hunting technique used by a New Zealand native fish.

Teacher Kit Hustler and students Ben Whittington and Zac Martin, year 12 and 11 respectively, filmed the freshwater banded kokopu leaping out of the water to snare an insect on the banks of the pool at Le Roy's Bush where it lived.

Their finding has been published in the New Zealand Journal of Zoology and could account for unexplained differences between the kokopu stomach contents and expected diets.

Previous studies showed the nocturnal species, which have poor night vision and whose diet consists of terrestrial insects, were able to detect insects which had fallen into the water.

It was thought the species were more opportunistic hunters, but until now the fish's stomach contents and stream drift samples didn't match up. The difference between the two in one study was equivalent to a 40 percent deficit in energy.

The group were at the stream in January as part of an NCEA assessment when they first noticed the jumping behaviour. Unsure of what the fish was aiming for, they came back in February and placed wax moth larvae on the side of the pool.

Each time, in less than two minutes, the fish leapt from the water and took the bait.

It shows rather than being passive nocturnal feeders, banded kokopu are active hunters.

Mr Hustler says Ben and Zac are excited to be published in a journal before they've left school and Northcote College is trying to get students involved in studying native species on their doorstep.

"The fact it's been seen in the middle of Auckland in a stream which is heavily polluted, by some people who happened to be there is a bit of a coincidence," he says.

"There's a lot of stuff to be discovered out there."

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