Big Eye Tuna

Big Eye Tuna

Rob & Scott Naysmith

I asked my son Scott to give me a hand with this article for two reasons, firstly to give both an old world and new age perspectives on the fishery.  Secondly for my own pride in seeing a young angler take the knowledge I gave him, expand on it, and then watch him share his knowledge with others.   That’s what angling should be about. 


I caught my first Big Eye tuna way back in the early 80’s, growing up in Natal we never caught these beasts so to be able to add one to my species list was quite an achievement.  I thought I’d gone a few rounds with George Forman when I was booked to fight the local bully.  It looked much like a Yellowfin, a fish we tried to avoid in those days, but there were a few anomalies and the fight was quite different.  Only back at the dock did the “fishiado’s” confirm that it was in fact a Big Eye, and to prove it they hauled out it’s liver.   In those days catching a Big Eye was a fairly rare occurrence, hard to identify and a fluke more than skill.   But times have changed, and we’ve learned so much about the species, it’s habits, and its beautiful oily steaks, that it is now possible to specifically target them.  But I urge everyone reading this article to use this knowledge sparingly and responsibly.


To target any species of fish, success comes from knowing and understanding the quarry, and the Big Eye Tuna is no exception.  So, let us start by describing the Big Eye, how you can identify it and the characteristics you can use in your favour.


The Big Eye (Thunnus obesus) is a tuna species spread across all oceans of the world.  Preferring cooler waters than the Yellowfin and Skipjacks, it is more likely to be found where the Longfin Tuna roam.  Rarely found in our waters with a surface temperature over 20 degrees C it appears that their optimum temperature range is between 10 and 15 degrees C, usually found below 40 meters. That said, an echo-sounder with the ability to show thermoclines becomes an added advantage when hunting Big Eye.


This species derives its common name from the unusually large eye compared to other Tuna species.  Now that is a vital clue in understanding and targeting Big Eye.  The big eye suggests that the species spends a major portion of its hunting life in the deeper, darker waters, which in turn indicates it can tolerate colder temperatures.  Now you’re beginning to understand where the Big Eye gets its ability to effortlessly empty a reel going straight down, through cold thermoclines all the way to the ground.   In fact, the Big Eye spends only about 5% of its day feeding in the top 40 meters of water, and that being predominantly early morning and late afternoon.


Another indicator of the amount of time these fish spend down in the cold depths of the ocean, is the high fat content of their flesh.  This makes them highly sort after by the sushi market and one of the tastiest eating Tuna in the world.


At first glance a Big Eye looks a lot like a Yellowfin however in younger fish, with their proportionally longer pectoral fin, they can be mistaken for a young Longfin until you look closely.  This pectoral length ratio reduces as they get bigger and the fin reaches between the first and second dorsal in adults.  The dorsal and anal sicycles do not get as long as those of a big Yellowfin and the finlets running from the top and bottom fins to the tail, are not bright yellow but more of a dusty mottled colour.  Of course, the eye is disproportionately larger than a yellowfin and it is generally a much more rounded fish, though I have caught some really fat Yellowfin as well.  The big tell-tale is the liver which is crinkle-cut as opposed to smooth. 


The Big Eye primarily feeds on cephalopods (squid, cuttlefish, etc.), crustaceans (shrimps, crabs, etc.) and almost any fish species it can find. Although fishing methods have become more refined, I still find squid to be their best bait, followed closely by a whole Skipjack.   However, when not specifically targeting them, most bait caught fish are taken on Pilchard in a chum line while fishing for Yellowfin.


The Big Eye caught in our Cape waters are often of a bigger class than our Yellowfin, with fish well over the 100kg mark being not uncommon.  Erwin Bursik holds the World and All Africa records for a fish of 156.5kg caught off Ghana, while Donavan Cole regularly catches smaller class Big Eye on a handline out in the deep off Angola, again showing the vast areas these fish roam.    The increasing catches of fish over the 120kg mark in Cape waters is an indication of the dedication to learning and understanding the species by the younger generation of anglers.



As a recreational angler, I found the best time of year for a Big Eye was from April through to June, our Autumn months when the water was cooling down.  In hindsight with what we have learned since those days, this would have been an obvious conclusion.  However, there a few of our younger anglers who have followed the progress of their friends and fellow skippers on the Tuna line and pole boats.  This has led to a much better understanding of the species and resulted in a more refined targeting with consistently better catches.


Now we have learned to start targeting the Big Eye from late September and early October, through to when the water gets too warm in mid to late November.   I’m sure that if we braved the cold weather and winter seas, we would find them in July and August as well.


The period April to June still stands as a productive time and being a calm period of year in the Cape, it makes Big Eye fishing much more pleasurable.


Fishing methods:

Before the introduction of chumming for Yellowfin behind Long-liners and trawlers, we located the Tuna by trolling.  Our target species was the Longfin in preference to Yellowfin, Yellowfin were a nuisance unless you were in a competition. But now and again you’d hook a Big Eye and curse until it either came to the boat or broke off. 


The general observation amongst the more accomplished anglers was that surface lures, predominantly Jetheads, (I’m talking before all the new designs came about), of a pink or brown colour, were most productive.  Diving lures caught a few fish, but surface lures were better.  Today I make use of slant faced and flat faced kona type lures in a pink / dark blue or pink / medium brown colour combination, action as the trick.  After dedicating a tanker load of fuel into figuring out what makes these fish tick, I finally discovered that ‘Big T’ in Plett make the best lures for targeting Big Eye. A lure which I call Smoking 30 (there is a market name for it) is deadly, my go-to lure every time … well there’s one secret gone.


However, the latest trend, and one which was never pursued until recently amongst recreational anglers, is the bait and drift method.   Maybe our lust for the Big Eye wasn’t what it is today that led to the delayed advancements in this method, who knows, but I must confess, it’s definitely the most productive way to target them.  Here is where our young anglers like Scott come to the fore, they practice this method and are way more successful than we older generation ever were.


The constantly rising prices for quality Sushi Tuna on the world market has led to massive strides in catch, production and preservation methods, through endless studies by some of the top scientists in the field.  This brought about a massive refinement in our approach to targeting Big Eye Tuna.  First were the Tuna Longliners, then came the trawlers, each taking increasing numbers of fish from the oceans resulting in International controls being implemented through bodies such as ICCAT, which monitors the Atlantic, our fishing ground.  And this is where our younger generation takes over ….


As a recreation angler we chat with, listen, watch and learn from our friends and skippers on the commercial boats, they know, through years of record keeping, when and where to target specific Tuna species.  From this we’ve learned to make use of baits in preference to lures, we’ve also learned that there are far more Big-Eye Tuna down below the thermocline than on the surface and that, at certain times of the year, they prefer certain baits to others.


Back to the biologic make-up of a Big Eye Tuna.  The primary indicator is the large eye, which is better suited to hunt in conditions of low light rather than bright sunlight … think Swordfish.  The flesh has a very high fat content, a result of spending long periods in cold water temperatures.   We know that they love squid and fish at certain times of the year … for the rest they like tiny crayfish type things and our crayfish didn’t last that long with my crew …  so, let’s leave that one.


Our conclusion, and reason we’re often successful … squid baits drifted just below the thermocline, almost Swordfish style, are the way to go.  Big Eye show a preference for Lolligo squid but will eat a Potter.   We’ve refined the traces and use 8/0 to 10/0 Mustad carbon circle hooks; hook-up rates are increased, and the fish stay on.  We use soft mono and don’t bother with fluoro-carbon, it’s a waste and hard.  Use 1.5mm to 2mm line sanded with 600 water-paper to take the shine off.   Balloons are handy so that you can control the distances between baits, as you drop deeper different currents come into play.  Fluorescence is a big key to attracting fish in the dark depths.


Bait fishing during the day can be good and an alternative when there’s nothing happening on the surface, but night-time is the most productive, and this is where you could run into either a Swordfish or a Big Eye.  They both come closer to the surface at night, depending on the brightness of the moon.  Day fishing requires that you fish deep, often below 60 meters, where the fish will almost come to the surface on a dark night.   Bright nights are from 10 meters to 30 meters.  Swords and Big-Eye feed deeper on a Full moon and shallower on a New moon … work out the depth accordingly.


Put the rod in the gunwale and be patient, it happens, and the game is on.



The Fight:

Big-eye have this ability to run from the surface, all the way down to digging sea-lice off the ground, deeper than what you’d ever believe you’d have to cope with. I’ve had fish strip a reel while going straight down …600m before you can blink, it’s crazy. The fighting style is much the same as a Yellowfin, they stay straight down and fight in clockwise circles (for the most part) as they tire.  Because the Big Eye will run much deeper than a Yellowfin, this is usually the first indicator of what you’ve hooked. 


Big Eye fight deep and know how to stay down there.  When the small of your back aches, your muscles burn and your arms stop listening to your brain, you know that you’re getting towards halfway, but how close is the question. The fight can last hours for the uninitiated, you gain line and lose line and eventually believe you’ll never get the fish to the top …  and then you begin to wish it would just break off. This is why I admire the determination of all those anglers who have stayed the course to land their Big Eye. 


The only way I’ve found to shorten the fight on these fish is to apply maximum drag after the initial run.  Stand at the gunwale and let the tip of the rod almost touch the water, lift it level with the reel and wind down hard.  You may only get a half turn on the reel but it’s the only way, you need to keep the fish’s head coming towards you and use its swimming to help.  When it can turn it’s head it will take line, so you need to hang in there and just keep going.  Ease slightly on the drag when it makes a dash then tighten up immediately it stops, remember that the drag on the line is greater when your reel is half full than when you started, and compounded by the friction of the water.


A good friend Wayne Lauffs landed a record fish of around 75kg, on a spinner with 15kg line class, in an epic battle where no quarter was given for what seemed like eternity.  I watched him break down to pulp, no harness, no mercy given, Wayne, I still admire your determination and achievement.



So, there you have it … disseminate the information we’ve given you, think like a fish, and go catch yourself a class Big Eye Tuna.   Next month we’ll give you an insight to locating them, the tackle, lures, bait rigging and traces we use to catch Big-Eye Tuna. But please, again I reiterate, only take what you need then stop targeting, leave some for tomorrow.