How Richmond River fish stocks are being assessed
May 9, 2008
This is part of the equipment being used to assess fish stocks in the Richmond River following the flood-induced fish kill in January this year.
The camera is one of two being used by researchers at Southern Cross University.
It’s called a ‘Seadog’, a remotely controlled vehicle (or ROV). ‘Seadog’ has a manipulator arm that can hold a bait stick and release it should any large predators take the bait.
Far North Coaster joined Dr Daniel Bucher (pictured with the camera), and his team this morning on the Richmond as they carried out their studies.
Dr Bucher, senior lecturer in fisheries and marine biology at the university, and his student researchers lay the camera on the river bed and, as fish feast on a bait of pilchards and squid, images are relayed back to an on-board computer.
Dr Bucher said it was a difficult task to gauge the extent of the fish kill.
However, there is something of a measuring standard: Dr Bucher said that the fish kill in the Ballina Quays area alone in January was the equivalent of a year’s catch by professional fishermen.
The NSW Department of Primary Industries 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, Chantelle Ianna, conducted surveys of fish populations in the lower estuary using baited remote underwater video,” Dr Bucher said.
“This pre-flood data set is one of few taken prior to the major fish kill event.
“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.”
Dr Bucher said the results would provide another useful data set to examine how fish stocks in the lower estuary are fairing after the fish kill in January 2008 which, like the 2001 kill, was caused by deoxygenated water following flooding.
It will take several months for the data to be processed and findings released.
PICTURES: Daniel Bucher with the seadog camera, the on-board computer, and the camera’s shots of fish feeding.