Hard to answer for sure.
Much of the market is in Asia; as you know, the largest fleets of long line ships come from that part of the world. What they bring back, they sell and distribute. I think China just surpassed Japan with it's fishing fleet, but they are a bit closemouthed about it.
I was able to find this excerpt about bill fish commerical fishing (not long line specifically..allkinds) in Hawaii.
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Hawaii's Billfish
Four species of billfish are caught in substantial quantities off the Hawaiian Islands:
* Pacific blue marlin (Makaira nigricans), kajiki or a`u;
* Shortbill spearfish (Tetrapturus angustirostris) or hebi;
* Striped marlin (Tetrapturus audax), nairagi or `au;
* Broadbill swordfish (Xiphias gladius) or shutome.
With the exception of shutome, billfish are harvested in the open ocean by the same fleets which land fresh tuna and they enter the same markets as tuna. Seasonality of species is evident, with Pacific blue marlin most available during the summer months, striped marlin most available in the spring and fall, and shortbill spearfish most available in the summer and fall. Shutome is predominant in spring and summer.
The same general procedures for proper care of tuna also apply to billfish. However, a handling problem specific to billfish is their susceptibility to gaping or "cracking" if the fish is bent.
In a gutted billfish, buyers can determine freshness not only by examination of the exposed flesh, but by squeezing the corner of the belly flap between thumb and forefinger. A rubbery texture indicates freshness, but if the fingers penetrate the flesh, quality is lower. Another indicator of lower quality in marlin is whether the small, finely-pointed scales break off or stick out after running a hand across the skin. Gutted marlin, like gutted tuna, will keep better if the belly cavity is well iced. Loined marlin should be bagged to protect the flesh from air and dehydration in cold storage. To extend the shelf life of gutted marlin, the blood line should be completely removed. If oxygen from the blood remains in contact with the flesh for a long time, the flesh may take on a somewhat rancid taste. Blood denatures quickly, so removal of the blood line will also improve the life of fresh fillets.
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The site is: http://www.state.hi.us/dbedt/seafood/intro.html
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and I think the Japanese names for marlin as sushi, suggest they eat it:
Kurokajiki=Kurokawa=Katsuokui (Blue Marlin)
Makajiki=Kajimaguro (Striped Marlin, Pacific Marlin)
and I think "Kajiki" might refer to all marlin in general.
(I think this is right, but if not, someone who knows will correct.)