The National- Tuesday, January 18, 2011
PAPUA New Guinea is keen to set up its own Pacific tuna tagging programme to cover fisheries observers in-post catch sampling and satellite-based supervision of vessels.
The US$3 million programme will be conducted by the secretariat of the Pacific community (SPC) and National Fisheries Authority within the exclusive economic zone for three years.
Tagging projects to better understand various aspects of tuna in the Pacific were done before.
The recovered data informed stock assessments of important tuna species and its main goal was to sharpen the accuracy of the estimates regarding how much tuna can be sustainably fished and help establish scientifically-based catch limits.
As of July of last year, nearly 15% of all tags had been retrieved and recaptures continued at a variety of unloading points.
Some 4,000 fish stomachs were collected and almost 3,000 Fatmeter measurements made to indicate the condition of the fish.
Analysis on about half of the stomachs showed nearly 200 different species out of some 55,000 counted prey.
The SPC’s programme has used almost 1,000 "archival tags" that get placed inside the fish belly and trail a pencil-length antenna on their outside.
The tags then gave precious details pertaining to the tuna’s behaviour, feeding times, depth habits and other factors.
Archival tags were considerably more useful than conventional tags, which offer information on growth, migration and mortality.
Tagged tuna have already been captured as far as 4,500km from the point where they were originally released, and can show up in locations as far removed as Thailand and Ecuador
SPC scientists have also travelled overseas to form collaborative arrangements with members of the tuna sector throughout the region as part of the follow-up to the main scheme.
Thus far, about 10% of the archival tags have been recovered and more are awaited.
This represents about 5,500 days of data for the stock assessment and modelling section of OFP, offering insights into tuna behaviour including:
* Tuna have been found to dive to depths exceeding 1000m, possibly to avoid predators;
* To maintain an ideal body temperature, they adjust their depth;
* Each species possesses a ‘favourite depth,’ evident as well in their diet; and
*Tuna are known to assemble under floating objects; data showed that these tuna remain nearer the surface than those in free schools, such that they become more vulnerable to fishing.