Anatomy and physiology Tunas in general, and especially bluefin, are champion swimmers. Every part of their inner and outer anatomy is fine-tuned for fast and efficient swimming, from their streamlined bullet shape and dragreducing finlets to oversized bands of aerobic red muscle (the “blood line”) for sustained distance swimming. All that swimming generates heat from muscle contractions, and tuna have special counter-current exchangers that trap the heat and focus it in their core and head. This type of partial “warm bloodedness” makes their muscles more efficient and powerful, boosts metabolism, and even improves their vision for feeding down deep in cold water and low-light conditions1. What this means for targeting bluefin: Stay mobile. Just because bluefin were in spot one day doesn’t mean they’ll be there the next week, or even the next day. They have no problem swimming dozens or even hundreds of miles in just a day or two. 68
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Be patient if they totally disappear. They could be in the same area and just down deep for a day or two, especially if the bait also sinks out. Since they can keep their body temps warmer than the surrounding water, it’s easy for them to feed deep in the low-light zone where bait is trying to hide. Make your gear invisible. Bluefin have excellent vision and are notoriously line-shy. For fishing live bait, use light line, a fluorocarbon leader, and the smallest hook you can get away with for the size of the bait. The tradeoff is that the bluefin’s hyper-efficient metabolism means you’ll be in for a long, hard battle. You can get away with using heavier gear at dawn or dusk when the low light makes your line harder to see. And of course, fly a kite! It keeps your line out of the water where bluefin have a harder time seeing it, meaning you can get away with heavier line and stand a better chance of actually landing the fish. Chill out. All that heat in the bluefin’s core rapidly degrades the quality
of the meat after the catch, and it increases the rate of bacterial growth. Getting your fish cold quickly will dramatically improve the end product you put on the table. Bleed your catch as soon as it hits the deck to remove a major source of heat from the core of the fish. Spike the brain to stop muscle contraction and prevent additional heat generation. Gut your fish to remove warm organs, and stuff the gut cavity with ice. A little seawater in your ice helps create a slurry to chill the fish even more. Plan to carry at least ¾-1 pound of ice per pound of bluefin you hope to catch per day, plus a quality insulated kill bag or cooler big enough to fit it all.
Diet Bluefin eat a wide variety of fishes and invertebrates based on what’s available. They’ve been known to eat mackerel, saury, juvenile rockfish, squid, red crab, and even krill2, and they’re locally famous for busting up on big spots of anchovy and chasing down flying fish. This wide variety of prey types spans a big range in how
