Secret life of rare fish shows a soft side

Scientists have used underwater cameras and radio tracking to spy on an endangered native fish species as they attempt to save it from extinction.

NSW Department of Primary Industries scientist, Gavin Butler, said the aim was to return the eastern freshwater cod (EFC) to the river systems they once inhabited.

“We’ve been studying the behaviour and preferred habitat of the EFC, tracking where they travel and filming their daily activities,” Mr Butler said.

According to Mr Butler the most surprising finding has been the role of the male EFC in raising their off-spring.

“Underwater footage has revealed that once females mate and spawn they leave the eggs in the care of the male,” he said.

“Male EFC aggressively guard the eggs until they hatch and protect young cod until they are old enough to fend for themselves. Unfortunately this territorial behaviour means the male is vulnerable to anglers.”

The Clarence and Richmond Rivers once teemed with this rare fish which is now found naturally in just two isolated tributaries of the Clarence.

A relative of the Murray cod, EFC was first identified as a distinct species in the 1980s and studies now show the fish likes to travel.

“We’ve tracked a number of fish in the wild and some have travelled more than 30 kilometres, over waterfalls and barriers to mate and feed.

“In future, this work will help us identify and remove obstacles in the river so they can freely move through the whole system.”

Mr Butler said results of his studies have been integrated into the EFC Recovery Plan which aims to secure existing populations and return cod to the rest of the river systems by improving aquatic habitat.

“Now that we have improved our knowledge of the EFC we’re in a much better position to ensure their future survival.”

The recovery plan provides a comprehensive list of actions and strategies to aid the recovery and natural viability of EFC populations by reducing threats, gaining a greater understanding of their biology and monitoring the results.