Tuna tagging 'even more important' during Covid-19 pandemic

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MAJURO — The tagging of over 6,000 tuna in the central Pacific over the past seven weeks is being hailed by scientists for the data it will provide to ensure accurate assessments of tuna stocks in the region.

 “The western and central Pacific is the only area in the world where tunas are sustainably harvested,” said Dr. Simon Nicol, the Pacific Community’s principle fisheries scientist who oversees stock assessments in the region. “Without the information from tagging, we wouldn’t be in a position to be confident that bigeye tuna is being sustainably harvested. Tagging data is fundamental in assessing the skipjack population. Without it, the assessment would be highly uncertain.”

The western and central Pacific tuna fishery — which involves fishing for skipjack, bigeye, yellowfin and albacore — is worth $6 billion annually.

Most islands depend on a combination of fisheries and tourism revenue to fund national budgets, but the coronavirus pandemic has largely halted tourism. “With global tourism effectively shutdown due to Covid-19, the income derived from tuna is even more critical for Pacific economies,” said Graham Pilling, the Pacific Community or SPC deputy director for the Oceanic fisheries program.

Nicol said the current tuna tagging effort, which started in August and is scheduled to finish this weekend, was of even more importance than usual because Covid-19 border closures have forced a halt to the use of independent fisheries observers on all purse seine and some longline vessels fishing in the region, reducing the flow of data that scientists use for stock assessments.

SPC has sponsored a tuna tagging program for two decades, with an estimated 450,000 tuna tagged and over 81,000 of those tags returned to the SPC, which is based in New Caledonia, for evaluation. SPC pays a reward for returned tags, many of which are returned by cannery workers, stevedores handling tuna transshipment in island ports, and artisanal fishers. The main challenge is getting return of tags, particularly the electronic ones. SPC offers a $250 reward for return of the electronic tags and $10 for the plastic tags.

 “We use the returned tags to infer the level of harvest by the commercial fishery,” said Nicol. “The return rates of 10-to-20 percent are very useful to determining fishing mortality.” SPC combines the data gleaned from tuna tags with fisheries data from industry and independent fisheries observers to generate regular stock assessments used by island fisheries departments for management of the resource.

 “Tuna is being fished well within sustainable limits,” Nicol said.

A small yellowfin tuna with an electronic tag protruding from its belly just before it was put back in the ocean by an SPC tuna tagging team. SPC photos



The SPC charter vessel Gutsy Lady on a visit to Majuro in the Marshall Islands during an earlier tuna tagging voyage.



Crew on board the SPC-chartered Gutsy Lady implant an electronic tag into the belly of a large yellowfin tuna during its current tagging voyage in Kiribati waters. Electronic tags record data on the ocean environment and behavior of fish that help scientists with assessments of tuna stocks in the region.

The crew onboard SPC’s chartered vessel the Gutsy Lady have tagged 6,387 tuna on a seven-week voyage in Kiribati and the Phoenix Islands Protected Area that ends when the vessel returns to Honolulu Saturday.

They have been using two types of tags. One is a conventional spaghetti-style plastic dart tag and the more sophisticated electronic tags that are surgically implanted, said SPC fisheries scientist Dr. Joe Phillips.

 “The electronic tags record information about the fish and the ocean environment,” said Phillips. “When the tags are returned, we evaluate the data stored on these electronic tags.” Scientists are able to learn things from the data stored on the electronic tags such as how much time tuna spend around fish aggregating devices or FADs, and school cohesion around the FADs.

The scientists said tagging is critical to show exactly how fishing pressure, climate change and improvements in fishing technology affect the health of the fishery.

Nicol said key to the success of the current tagging voyage is cooperation with the fishing industry. “This is one of the most successful trips,” he said, adding this reflects the “fantastic collaboration with industry, which has been providing daily updates from their electronic monitoring (of tuna schools) to direct us (crew on the Gutsy Lady) to areas of expected high tuna abundance.”

Phillips said good support from the Kiribati government facilitated the voyage in Kiribati’s vast exclusive economic zone. The collaboration with the tuna industry and Tuna Commission members in the region is what makes the tuna tagging program work. “The tagging benefits everyone,” Phillips said.

Because of the volume of tuna caught annually and the value to industry and the islands, credible stock assessments are essential to ensuring fishing rules and harvest limits can be made based on solid information, the two scientists said. “By our estimate, the stocks are in good shape,” said Phillips.

November 2020 pssnewsletter

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