Bigeye tuna

[4] Bigeye tuna are found in the open waters of all tropical and temperate oceans, but not in the Mediterranean Sea.

[7] The eyes of bigeye tuna are well developed and with a large spherical lens allowing their vision to function well in low light conditions.

[5] Conventional tagging data and counts of growth increments in otoliths (ear bones) of bigeye tuna have recorded a maximum age of 16 years.

Spawning takes place across most months of the year in tropical regions of the Pacific Ocean, becoming seasonal at higher latitudes when sea surface temperatures are above 24 °C.

[13][19][20][21][22] One study suggested an annual migration influenced by water temperature, specifically that near the surface.

[23] Bigeye tuna primarily feed on epipelagic and mesopelagic fish, crustaceans and cephalopods.

[15][24] Globally, approximately 450,500 metric tonnes of bigeye tuna were caught by commercial vessels in 2012.

Various conservation measures have been introduced by the regional fisheries management organisations which apply to particular sized vessels and fleets and include measures such as spatial and temporal closures, trip duration limits, observer requirements and limits on catches.

[35][36][37][38] Bigeye tuna catch rates have declined abruptly during the past half century, mostly due to increased industrial fisheries, with ocean warming adding further stress to the fish species.

Drawing by Kawahara Keiga , 1829
Bigeye tuna caught with three-pole one-line rig
Global capture production of Bigeye tuna ( Thunnus obesus ) in thousand tonnes from 1950 to 2022, as reported by the FAO [ 25 ]