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2 December 1998 |
Ref 98/281 |
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Hi-tech fish tags have been successfully tested for the first time on black marlin.
The tags are programmed to be released from a fish at a given time and then transmit information to a satellite.
A year ago a female black marlin weighing more than 600 pounds was tagged and released off Cairns, after having been caught by an Australian tuna longliner.
Last week, the Pop-up Satellite Tag disengaged from the fish at the programmed time, floated to the surface and transmitted information to the satellite revealing that the marlin had returned to within 40 nautical miles from where it was tagged and released.
"This is great news because we now know that this cutting-edge technology works, and that the tags can stay on the fish for a long time, in this case a year," says CSIRO Marine Research scientist John Gunn.
Black marlin are targeted by game fishers off Cairns, but little is known about their travels when they leave the coast for the ocean, he said.
"We know that black marlin come to the Coral Sea to spawn between September and January, with some then travelling down the Queensland coast before migrating out to sea between January and February."
"What we don't know is if there is exchange of marlin between the Pacific and Indian Oceans, or whether there are separate stocks."
Any black marlin caught as bycatch by the Australian domestic tuna fishery is required to be returned to the water. Most are returned in good condition.
"Many black marlin fatalities occur in both the Indian and Pacific oceans where distant water tuna fleets catch them as bycatch. This makes information on large-scale migration patterns important for management," he said.
The tag that surfaced last week was the first of two prototype Pop-up Satellite Tags tested on black marlin a year ago.
The research, which also tested Pop-up Radio Tags, was funded by CSIRO and the Fisheries Research and Development Corporation and conducted in collaboration with Julian Pepperell of Pepperell Research.
It involved extensive co-operation with the recreational and commercial fishing industries.
"Now we know that the satellite tag technology works, the next step is to release hundreds of these tags on black marlin, each with different release dates. That way we will end up with a data set of hundreds of points in the ocean showing where these marlin migrate," says CSIRO's Tim Davis who co-leads the research.
"The next advance in tagging technology will be to develop tags that log information on factors such as location (from light measurements), depth, water temperature and time, and then pop-up to the surface," he says.
Prototypes of these tags are currently being developed and will be tested in early 1999.
"Using this technology it will be possible to trace the life of a marlin over a year or more, providing a much clearer idea of marlin migration, and where the greatest fisheries threats are likely to be occurring," says Tim Davis.
More information from:
John Gunn 03 6232 5375
0418-126546
Katherine Johnson 03 6232 5113
(Australia's largest scientific research organisation)
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