Chasing elusive octopuses in the dead of night


Julian Finn and John Ahern remove a light trap from the waters near Lizard Island.
Image: Gary Cranitch.

 

Tuesday 17 February 2009
 
WHILE the rest of the CReefs team on Lizard Island sleeps, Julian Finn is hard at work.
 
To catch his prey, Julian needs to be out on the reef in the cover of darkness, specimen bag in hand.
 
It's hard work, but it's what needs to be done in order to catch an octopus.
 
Julian works at Museum Victoria and has just finished his PhD on ocean octopuses He is being assisted by John Ahern, from Melbourne University's Zoology Department.
 
As well as chasing octopus, the pair is after other cephalopods such as cuttlefish and squid; however the main focus is finding the 14 types of octopus recorded around Lizard Island.
 
Included in that 14 are species that have only been examined several times, and one that has only been identified from a single photograph.
 
Julian said his aim for this trip was to expand the knowledge base about the Lizard Island species.
 
"We want to collect enough specimens to really understand the species, but also for other things like genetic analysis," he said.
 
Unfortunately for Julian and John, octopuses like dark crevices and safe hiding spots – which coral reefs offer in abundance.
 
Thus the night reef walks.
 
Hoping to catch an octopus strolling across a reef at night isn't the only weapon at Julian's disposal, however.
 
He and John have also laid light traps, which attract octopus larvae, and octopus pots, which offer the creatures a place to hide.
 
But what works in temperate waters doesn't always work in the tropics, as the cephalopods have less reason to wander into a trap.
 
"In a coral reef system they're generally hard to find because of the amount of cover [available]," Julian said.
 
Still, Julian and John have found some of what they've been looking for and have set up some tanks with their finds.
 
They've so far targeted the inter-tidal octopuses, which come out at night during a low tide, but will continue to look for all 14 types.
 
Julian said he hoped to be able to continue the research into the cephalopods across the rest of the CReefs sites.
 
He said the three sites – Lizard, Ningaloo and Heron Island – had 39 recorded species of octopus, with 19 of them undescribed.