Underwater video to check fish stocks

Published 8 May 2008

A video survey will be done by researchers at Southern Cross University to assess several fish stocks in the Richmond River before and after the January 2008 fish kill.

The NSW Department of Primary Industries (DPI) has provided funding to Southern Cross University to repeat a small study of fish populations in the lower estuary so that the data can be compared with pre-flood results.

The work follows on from the results of fish surveys, conducted in February by the NSW DPI and commercial fishers, which found that fish stocks were at sustainable levels allowing the river to be reopened to fishing.

“In 2004 an honours student at Southern Cross University’s School of Environmental Science and Management conducted surveys of fish populations in the lower estuary using baited remote underwater video (BRUV). This pre-flood data set is one of few taken prior to the major fish kill event,” said Dr Daniel Bucher, senior lecturer in fisheries and marine biology at the University.

“The method involves lowering a digital camera in an underwater housing into the water with a bait held in front of the lens on a long stick attached to the housing. Fish abundance can be compared by measuring how long it takes to attract a certain number of fish to the bait in a defined time period.

“The camera was deployed in four habitats in 2004 – ‘shallow rocky habitat’ (near Mobb’s Bay training wall), ‘deep rocky habitat’ (along South Wall and near the Ballina aquatic centre), ‘shallow sandy habitat’ (sand banks off the Ballina RSL) and ‘deep sandy habitat’ (the main channel in front of the RSL club). Each deployment lasted 45 minutes. The method was repeated three times at each habitat type.”

In 2004, the fish attracted to the baits were mostly bream at the rocky sites and whiting at the sandy ones, but other species included puffers, trumpeters and stingrays.

Southern Cross University researchers will repeat the survey in the same locations, this time using two different types of video camera. One camera being used is ‘Seadog’ a remotely controlled vehicle or ROV. ‘Seadog’ has a manipulator arm that can hold the bait stick and release it should any large predators take the bait.

While a standard digital camera stores its footage on a tape to be viewed on retrieval, the ‘Seadog’ camera transmits the images back to the boat where they can be monitored live and recorded.

The results will provide another useful data set to examine how fish stocks in the lower estuary are fairing after the fish kill in January 2008.

Photo opportunity: Researchers will be conducting the survey from the Baysail boat ‘Discovery’ on Friday, May 9. Media are invited to join the researchers on the boat, which will be leaving the Fawcett Street wharf at Ballina at 9am.

Media contact: Zoe Satherley, Southern Cross University media officer, 6620 3144 or mobile 0439 132 095 or Phil Bevan, NSW DPI, Wollongbar 6626 1350 or 0429 458 053.