Pacific Tuna Tagging Project

Several PIFSC staff members have been contributing to the work of the Pacific Tuna Tagging Project (PTTP), a major collaborative tuna research initiative in the western and central Pacific Ocean (WCPO). The PTTP is being implemented by the Secretariat of the Pacific Community’s Oceanic Fisheries Program, the National Fisheries Authority of Papua New Guinea, and the members and participating non-members of the Western and Central Pacific Fisheries Commission. Pierre Kleiber, a scientist in the Center’s Fishery Biology and Stock Assessment Division (FBSAD), serves as a member of the PTTP steering committee and has been actively engaged in analysis of PTTP data. Keith Bigelow (FBSAD) and Russell Price (PIFSC Information Technology Services group) have spent time at sea on PTTP tuna tagging cruises.

Beginning in 2006 and extending through 2010, the PTTP has so far accomplished the release of 259,663 tagged skipjack, yellowfin and bigeye tuna over a broad area of the WCPO. The project is the third large-scale tuna tagging campaign undertaken in the WCPO, preceded by the inaugural Skipjack Survey and Assessment Programme (SSAP) from 1977-1981 and the Regional Tuna Tagging Project (RTTP) from 1989-1992. Tag release and recovery counts and locations for the three tagging campaigns are shown in the accompanying graph, which was presented at a PTTP review meeting in February 2010. During the SSAP campaign, WCPO tuna fishing was dominated by pole and line fisheries, while during the RTTP and PTTP campaigns, purse-seine fisheries dominated. Over the span of these tagging campaigns, there was a massive increase in the use of Fish Aggregating Devices (FADs), and the annual WCPO tuna catch increased from 300,000 mt during the SSAP years to 2.4 million mt in recent times.

Skipjack Survey and Assessment Programme (SSAP), 1977-1981
Number of fish released by location during the 1977-1981 Skipjack Survey 
        	and Assessment Programme (SSAP). The colors blue, yellow, and red indicate skipjack (SKJ), yellowfin (YFT), and 
        	bigeye tuna (BET), respectively. Number of fish recovered by location during the 1977-1981 Skipjack Survey 
        	and Assessment Programme (SSAP). The colors blue, yellow, and red indicate skipjack (SKJ), yellowfin 
        	(YFT), and bigeye tuna (BET), respectively.
  Releases Recoveries
SKJ 147,507 93.7% 7,126 4.8%
YFT 9,884 6.3% 281 2.8%
BET 65 0.0% 0 0.0%

Regional Tuna Tagging Project (RTTP), 1989-1992
Number of fish released by location during the 1989-1992 Regional Tuna 
        	Tagging Project (RTTP). The colors blue, yellow, and red indicate skipjack (SKJ), yellowfin (YFT), and 
        	bigeye tuna (BET), respectively. Number of fish recovered by location during the 1989-1992 Regional Tuna 
        	Tagging Project (RTTP). The colors blue, yellow, and red indicate skipjack (SKJ), yellowfin 
        	(YFT), and bigeye tuna (BET), respectively.
  Releases Recoveries
SKJ 98,401 67.1% 12,447 12.6%
YFT 40,075 23.7% 4,950 12.4%
BET 8,074 5.5% 975 12.1%

Pacific Tuna Tagging Programme (PTTP), 2006-2010
Number of fish released by location during the 2006-2010 Pacific Tuna 
       	 	Tagging Programme (PTTP). The colors blue, yellow, and red indicate skipjack (SKJ), yellowfin (YFT), and 
        	bigeye tuna (BET), respectively. Number of fish recovered by location during the 2006-2010 Pacific Tuna 
        	Tagging Programme (PTTP). The colors blue, yellow, and red indicate skipjack (SKJ), yellowfin 
        (	YFT), and bigeye tuna (BET), respectively.
  Releases Recoveries
SKJ 166,152 64.0% 21,667 13.0%
YFT 78,076 30.1% 10,715 13.7%
BET 15,435 5.9% 2,057 13.3%
Numbers of releases and recoveries in the three WCPO tuna tagging campaigns. Release locations are shown in the maps on the left and recovery locations are shown on the right. The colors blue, yellow, and red indicate skipjack (SKJ), yellowfin (YFT), and bigeye tuna (BET), respectively.

A major objective of the PTTP is to improve stock assessments for skipjack, yellowfin, and bigeye tuna in the WCPO. One improvement will be enabled by direct input of tag recovery data into the stock assessment models used to determine the status of the stocks. Another improvement will result from better understanding of tuna movement patterns, which will help scientists to better design the spatial structure of the assessment models and how the models represent fish movement. To investigate movement patterns, scientists have been developing a tag movement model enabling estimation of tuna movement coefficients from the tag data. This involves the rebuilding of a model applied almost two decades ago to the RTTP data on a smaller geographic scale (see graph below). This effort also involves applying yet larger-scale models. With the changes in FAD deployment, it is hoped PTTP data will enable scientists to better understand how FADs might affect tuna movement behavior in the region.

Tag dispersal and recoveries (aggregated by half-degree square) over time from a single set of 
            releases in one month off Papua New Guinea. Arrows depict estimates of north, south, east, and west 
            movement coefficients from the current model. The inner rectangle shows the geographic range of the 
            original model applied to RTTP data.
Tag dispersal and recoveries (aggregated by half-degree square) over time from a single set of releases in one month off Papua New Guinea. Arrows depict estimates of north, south, east, and west movement coefficients from the current model. The inner rectangle shows the geographic range of the original model applied to RTTP data.