“Indian Ocean Tagging Program Achieves 7,000 Tags Returned” ff

A lot of countries depend on tuna fish.  But are we fishing it sustainably? To attempt to provide answers to this vital question, a major tagging project is underway in the Indian Ocean. It involves tagging tens of thousands of fish, putting them back in the ocean, and – most importantly - recovering them. Up to date a total of 120,000 tropical tuna (Yellowfin, Bigeye tuna and Skipjack) has been tagged and 7,000 of these tags have been recovered and reported to the project.

A publicity recovery and reward scheme is in operation in every coastal country of the region and beyond to encourage those who recover tagged tuna to provide reports and to ensure a smooth return of the recaptured tuna to the RTTP.  This system is based on the setting up of a network of National counterparts that help the project with the implementation of a strong publicity campaign and an efficient tag recovery and tag return system.

Finders are asked to provide tag number, fish fork length, address, tuna species and date/location of catch and in return are awarded a prize that can go from a T-shirt for the return of YELLOW tags and respective information, to cash prizes for the return of fish that carries a WHITE or a RED tag.

Recoveries distribution between fishing gears show’s the overwhelming importance and participation of the purse seine fleet with 95.6% of total recoveries. The remaining 4.4% mainly comes from the recoveries made on board the project tagging vessels (poll and line fisheries) and from artisanal fleets, 15 recovered using troll line (mostly from Comoros), 10 from gillnet (Sri-Lanka, Maldives and Oman) 5 from hand line fleets (from Kenya and Tanzania) and. To date, only 7 tags have been reported by longliners operating in the Indian Ocean but the project hopes that the reporting rate for this fleet will increase in the future.

Until now, 67% of the total recoveries have been reported by the stevedores when unloading or trans-shipping the catch, while 12% have been recovered by the fishing crews while at sea fishing and 9% have recovered in the canneries while sorting, ranking, butchering and cleaning the fish.

Recovery species composition is presently dominated by skipjack recoveries making up to 65% of the total recoveries, yellowfin tuna follows with 29% and in last with 6% comes the bigeye tuna recoveries. This trend is expected to change when the purse seine fleet moves to the yellowfin spawning grounds, between Chagos and Seychelles, from December 2006 to March 2007.

Tagged fish total time at liberty overall distribution shows a large proportion of long-time recoveries without any remarkable differences between the three species (please note that the following data and figure are very preliminary[1]), with a proportion of recoveries after 120 days of more of 61 % for yellowfin, 68 % for bigeye and 65 % for skipjack tunas.

Recoveries at sea for which date and position of recovery are known offer the possibility to build maps with a straight line between the tagging and the recovery positions. These maps suggest a strong north-east movement for all species from the Tanzania area along the coasts of Somalia and also some movements from Tanzania towards the Mozambique Channel.

Figure 1: “Time-at-liberty” of all the recoveries

Figure 2a:Theoretical travel between tagging and recapture for the Bigeye recovered at sea in 2005 and 2006

Figure 2b: Theoretical travel between tagging and recapture for the Yellowfin recovered at sea in 2005 and 2006

Figure 2c: Theoretical travel between tagging and recapture for the Skipjack recovered at sea in 2005 and 2006