Bigeye/Yellowfin Info

[Spoonplugger]

This info is not copyrighted.

The info sheds a little light on the habits of these 2 species and the quantity caught commercially.

Quote:

PICES XIV FIS_Paper-2518 Oral

The vertical and horizontal distribution of bigeye (Thunnus obesus) and yellowfin tuna (Thunnus albacares) related to ocean structure
Eun Jung Kim1,2, Suam Kim1, Dae-Yeon Moon2 and Jeong-Rack Koh2

1 Department of Marine Biology, Pukyong National University, Busan, 608-737, Republic of Korea. E-mail: eunjung.kim@gmail.com

2 Tuna Lab. National Fisheries Research & Development Institute, Busan, 619-902, Republic of Korea

To delineate the relationship between tuna populations and their ecological characteristics in the tropical and subtropical ocean, Korean longline fishing data on bigeye (Thunnus obesus) and yellowfin (Thunnus albacares) tuna were analysed. The National Fisheries Research and Development Institute of Korea collected totals of 211 sets in the Central East Pacific Ocean during August 1999 – October 2000, and TAO array information was used to understand vertical structure of water properties in surface layer. The depths of hooks in longlines indicated that the vertical catch rates of bigeye and yellowfin tuna were different, and the thermocline seemed to be important factor to determine the vertical habitat of two species: High densities of bigeye tuna were found between 9°C-13°C, just below the thermocline (>290 m), while yellowfin tuna resided in broad range (10°- 20°C) of temperature above the thermocline (150 – 300 m). There was no strong seasonal difference in vertical distribution, but different depths of the mixed layer in eastern and western Pacific caused different vertical location of tuna species. The bait was also analysed for selectivity. Five kinds of main baits are used in this tuna fishing – mackerel, horse mackerel, squid, sardine and herring. Among the baits, sardine and horse mackerel were more frequently chosen by both species. Understanding the relationship between bait animals and physical environments is important for better fishing efficiency.

PICES XIV FIS_Paper-2444 Poster

Stock assessment of bigeye tuna (Thunnus obesus) in the Pacific using the AD model builder
You Jung Kwon1, Dae Yeon Moon2 and Chang Ik Zhang1

1 Pukyong National University, Daeyeon3-dong, Nam-gu, Busan, 608-737, Republic of Korea. E-mail: cizhang@pknu.ac.kr

2 National Fisheries Research & Development Institute, Busan, 619-902, Republic of Korea

The bigeye tuna (Thunnus obesus) inhabit warm, temperate, and very deep waters throughout the world. Most bigeye tuna are caught in the Pacific Ocean, but they are also found in the Indian and Atlantic Oceans. In 2003 total annual catch of bigeye tuna was 51,600 mt, and the catch by Korea was 14,400 mt, accounting for 28% of the total catch. The annual catch of bigeye tuna tends to increase recently, but the stock condition is still unknown at this stage. In spite of the increasing demand for conservation and rational management for this species, stock assessment has not been attempted yet in Korea. In this study, we conducted a preliminary stock assessment of bigeye tuna in the Pacific using the AD model builder. A strong management action for the bigeye tuna is urgently needed for the conservation and sustainable use of this species, based on the result of stock assessment.

Unquote

[Pilar]

High densities of bigeye tuna were found between 9°C-13°C, just below the thermocline (>290 m)

600 to 1000 ft, light stick and squid.

[ron m]

Thanks Jerry.

[Reef Diver]

Good Read
Now...how do we catch one?
Next time we get into Humbolt Squid out of Port Orford
I'll know what their good for.
Thanks Jerry

[TillamookChinook]

Maybe you can give the Dogs a report on the high densities of Big Eye Tuna in deeper water below the thermocline.

Good Luck!!

TC

[Spoonplugger]

Originally Posted by TillamookChinook

Maybe you can give the Dogs a report on the high densities of Big Eye Tuna in deeper water below the thermocline.

Good Luck!!

TC

The quoted gives a very good report, however, disturbing:

"In 2003 total annual catch of bigeye tuna was 51,600 mt, and the catch by Korea was 14,400 mt, accounting for 28% of the total catch. In this study, we conducted a preliminary stock assessment of bigeye tuna in the Pacific using the AD model builder. A strong management action for the bigeye tuna is urgently needed for the conservation and sustainable use of this species, based on the result of stock assessment."

My conclusion:
51,600 metric tons is a huge volume! It appears that Korea, who caught 28% of that, could care less at this point in time about conservation. The report definitely indicates a depletion.