Pacific tuna tagging: what to do with the numbers?
12 March 2010, Secretariat of the Pacific Community (SPC) - Twenty scientists gathered recently at an International Tuna Tagging Workshop held at the Secretariat of the Pacific Community's (SPC) headquarters in New Caledonia, reports www.megafishnet.com with reference to SPC.
The world's largest ever tuna tagging project has released over 250,000 tagged tuna into the equatorial Western and Central Pacific Ocean and 35,000 tags have already been recovered. The data being collected will help in sustaining and protecting the world's largest resource of tuna.
The joint SPC/PNG National Fisheries Pacific Tuna Tagging Programme started in August 2006 in Papua New Guinean waters, where 15% of the world's tuna is caught. In 2007, funding from the New Zealand government (NZD 5 million) and European Union (EUR 1.56 million) enabled the operational area of the project to be extended to cover the whole of the equatorial Western and Central Pacific Ocean. The last tagging cruise ended in October 2009. For around 90 days at a time, a 30-strong team of experienced Solomon Islands fishermen and SPC biologists roamed the seas on a pole-and-line fishing vessel, gently easing the fish on board to measure, tag and return them to sea within 15 seconds.
Most tags are thin rods inserted under the tuna's dorsal fin. Bigger fish were given express surgery and sent back to swim with an archival tag. The thin tags carry only a serial number, but the hi-tech archival tags keep track of geographical movement. In simple terms, the tag measures the light throughout the fish's journey. The data is then interpreted based on sunrise and sunset schedules for each time zone.
A vast communications operation was rolled out to inform fishermen, tuna canneries and fishery agencies around the globe about the tagging project. Posters in 16 languages promised a reward for every tag sent back to SPC. The recovery rate, close to 14%, has improved on rates attained during similar campaigns in the 1970s (4%) and 1990s (11%). Tony Lewis, Programme Coordinator, says, "We had one person working half time on communications. Next time, we need to dedicate more effort to this crucial task."
From field to laboratory
The results of the tagging project will provide information on various biological and fishery processes such as exploitation rates, mortality, movement, growth rates, and spatial and temporal variability.
The SPC team met last week with representatives from the Indian Ocean Tuna Commission, the Inter American Tropical Tuna Commission and PNG National Fisheries. They were joined by independent leaders in the field of data analysis from the USA (University of Hawaii, National Oceanic and Atmospheric Administration, National Marine Fisheries Service) and New Zealand (National Institute of Water & Atmospheric Research) for an analysis workshop. The agenda for the week centered on modelling approaches, with the main aim being to prioritise the use of the tagging data for the Western and Central Pacific Ocean to answer critical fisheries management questions.
The output of this meeting will be a work plan for the months ahead for transforming statistics into useful information for fisheries. As Brian Kumasi from PNG National Fisheries puts it, "The growth of the tuna industry in the Pacific over the last decade has occurred in parallel with the growing use of FADs (fish aggregating devices). It is really exciting that we now have data that can measure the impact of these FADs on the quantity and quality of tuna in the region. This information, in addition to the other analyses that are planned, will lead to better management of our shared fishery resource."