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What is a ‘true’ billfish?

By Staff | Jan 4, 2018

After a late start and having the lures in the water for only 30 minutes, little action was expected for some time. The lures in the trolling pattern were dutifully running in the wakes, though the deckman had a difficult time seeing this due to the intense glare of the mid-morning sun. With eyes shaded but straining, the deckman almost missed the long, slim foil rising up out of the water just behind the short rigger off the portside.

Nearly unnoticeable against the shimmering chaotic backdrop of the turbulent surface, the blade nimbly slashed back and forth at the lure. With instincts honed from years on the water, the deckman responded quickly, rushing to the rod and yelling out “BILLFISH!”

Whether it’s an agile striped marlin quietly sneaking up behind the pattern, or a BIG blue marlin crashing her enormous bulk down onto a trolled lure or bait, there is hardly a group of fish as exciting as the sailfish, spearfish and marlin, collectively known as billfish. A quick glance at such a fish gives clues to their namesake.

Their upper jaw projects far past the length of the lower, creating a slender, pointed “bill.” They have fusiform (torpedo-shaped) bodies; stiff, lunate tails; two keels on each side of their peduncle (region between tail fin and body); and pelvic fins that resemble long slivers.

There are nine billfish species, though some researchers feel that Atlantic and Pacific sailfish are two separate species. A similar contention exists for Atlantic and Indo-Pacific blue marlin. There are also a few fish with characteristics similar to billfish but are sufficiently different to be classified in their own groups and not considered “true” billfish.

The true billfish are those from the Istiophoridae family and include sailfish, spearfish and marlin (black, blue, striped, white). All are highly migratory marine predators found worldwide in coastal and pelagic tropical and subtropical waters.

Those fish that appear to be billfish, but are not, include needlefish, ballyhoo and swordfish. Needlefish and ballyhoo are inshore, surface-dwelling fish often used as bait. The upper and lower jaws in needlefish are elongated and also carry many needle-like teeth. A ballyhoo’s bill actually protrudes from the lower, rather than upper, jaw.

The fish most often associated with the billfish is the swordfish. Swordfish are classified into the Xiphiidae family. While they look very much like marlin, there are important differences.

A swordfish’s bill is very long and, unlike a billfish, flattened into a sword shape. Additionally, with bodies that are much rounder, dorsal and pectoral fins that are sickle-shaped and do not fold down, absent pelvic fins and only a single, large caudal keel on each side of the peduncle, swordfish are not true billfish.

All billfish can be caught using similar methods; the biggest difference is often the size of the bait used. They are fast growing, indiscriminate eaters, seldom refusing any potential prey. Indeed, the limiting factor seems to be what they can fit through their mouth. Studies on billfish stomach contents confirm this, and also that they are not above eating their own species.

Intrepid anglers will spend fortunes and lifetimes in pursuit of billfish. Catching one is an unforgettable spectacle. When excited, such as when chasing prey, billfish will flare their fins and “light up.” Fin tips, highlights and stripes illuminate as billfish explode with iridescent purples, blues and greens.

All are extremely fast swimmers and apt to take to the air. When hooked, an angler can expect blistering runs, unexpected direction changes, violent head shakes, somersaulting jumps and thrilling tail walks. Large marlin will also sound, swimming deep down beneath the boat, frustrating the angler with its refusal to budge.

With billfish, there is also an element of danger. Many an unwary and unlucky angler has been pulled overboard by a rampaging marlin. Even more alarming is the threat of being speared or slashed as the fish is being boated. And it is not unheard of for a billfish, either intentionally or accidentally, to charge and spear the boat – or even worse, to leap into the cockpit. If given the chance, billfish will fight to exhaustion and beyond.