Scientists are attempting to reduce the amount of bycatch in the tuna industry by utilizing sonar technology to better understand the number of fish species and the kind of fish that can be targeted, according to new research done under the sponsorship of the International Seafood Sustainability Foundation (ISSF).
In the research report, titled "Acoustic Discrimination of Tropical Tuna," the ISSF team's findings address a chronic challenge for commercial fishing fleets: identifying and harvesting mature, sustainable tuna while limiting bycatch.
“If you're working with land animals, you can walk right up to the herd and count them by size and species. But, typically, fish are out of your reach, hard to see, and constantly moving in three dimensions,” corresponding author Gala Moreno, Ph. D., explained in a press statement.
The new paper noted the potential offered by acoustic techniques to better inform vessels on which drifting fishing aggregating device (DFADS) to target. New technology can ascertain which are the more productive FADS as well as how to discriminate between fish species in the future.
The researchers said fishers face the constant challenge of working with FADs by avoiding fishing pressure on bigeye and yellowfin tuna, but permitting fishing on skipjack tuna.
“This manuscript provides first data on tropical tuna acoustic discrimination to date, that could be used for selective fishing with DFADs. Given the clearly distinct acoustic frequency responses found between skipjack and bigeye tuna, the potential and benefits of applying multi-frequency acoustics to discriminate species with swimbladder (yellowfin and bigeye) from species without swimbladder (skipjack) is confirmed,” the paper stated.
The report noted that these positive results can encourage taking the next step that is needed to obtain the acoustic mask required to determine the proportion of the three main tuna species found at DFADs.
Acoustic technology will be able to support tropical tuna conservation and thus help fishers target catch sustainably. The technology also has "an indispensable fishing tool” that purse seine vessels targeting tropical tunas can use to detect tunas and evaluate school size.
“Our research opens the door to several positive developments," Moreno said. "Faster growth of knowledge about the acoustic properties of tropical tunas; the advantages of close collaboration with commercial operations in support of science; definition of the conditions necessary for applying this technology for selective fishing; and projections of other uses of direct acoustic observations, as direct indices of tropical tuna abundance, to support tuna conservation."
The paper looks into a future that could help purse-seiners selectively target sustainable species, save fuel, and reduce marine-engine emissions by guiding vessels more directly to the right fishing grounds and reducing wasteful bycatch and the mortality of vulnerable species.
