By Scotty Kyle

I am probably the most sought-after species for extreme sport fishing anywhere in the world. While I support hundreds of companies and thousands of people in sport fishing enterprises, I also provide thousands of tons of food to many countries. My proper scientific name is Makaira nigricans. We first came to sport fishing prominence in the 1920s and 1930s in the Caribbean Sea, where we inspired such legendary stories as The Old Man and the Sea by Ernest Hemingway. Then our popularity spread to many other tropical areas of the world. There are now sport fishing operations dedicated to seeking my species out in many areas, from Hawaii to Portugal, Australia, South Africa, and many other countries in between. I am Atlantic blue marlin.

Largest of the Billfishes

There are about ten species in my family, the Istiophoridae, but mine is the largest. We attain a mass of over 820 kilograms (1,810 lbs.), but I, as a male, will only grow to about a quarter of the size of my sisters. I have a very close cousin, the Indo-Pacific blue marlin (Makaira mazara), that inhabits other tropical oceanic areas of the world. Other family members include the black, white, and striped marlin, as well as sailfish, swordfish, and spearfish, all of whom are collectively called billfishes.

Built for speed

We are all roughly the same shape: an elongate body with a spear-like bill in front and a sail-like dorsal fin sticking up sharply on our backs. We are an extremely hydrodynamically shaped fish, to the extent that even the fins on our sides can fold into grooves along our bodies to reduce water resistance. This makes us probably the fastest swimmers in the ocean and leads to our ability to travel extremely long distances, as well as to our famous fighting abilities. We are also well known for repeatedly leaping high out of the water when hooked and often successfully throwing hooks or lures from our mouths.

Colour, eyes, bill, and teeth

We are very dark above, either dark blue or even black, but our undersides are much paler. We are also renowned for our ability to change colour rapidly, especially when stressed or captured. Our mouths are big but lack large “shark-type” teeth, as many small file-like teeth are enough to hold and cut up the food that we eat. We have large round eyes that help us spot and home in on our prey, which consists mostly of fish, both small and large, but also squid and anything else we come across.

Our bill has evolved to assist us when we attack shoals of small fish. We stun or damage them as we smash into a shoal and then circle back to gulp in the injured fish. We can also use our bills to stun individual larger fish or other prey and, sadly, many sport anglers have recognized this. When we hit a bait or lure, they often release the line and fool us into taking the bait. We do not, as has been suggested, use our bills to attack humans or other predators.

A Life in the Blue Water

Because we are such a charismatic and important species, a lot of time and effort has been directed at us, our biology, and our life history. As adults, we are nearly completely a blue-water fish. We rarely come close to shore and, although we mostly stay in the upper reaches of the oceans, we much prefer deep water below us.

Where I live and roam

Apart from some spawning migrations, there is a general movement of many blue marlin from more tropical to cooler areas in summer, followed by a return in the fall. Much of our habits and movements still remain unknown, but the annual summer migration towards the Portuguese coast by some of us is recognized and heavily exploited.

We are usually solitary animals as adults, true wanderers of the open sea, yet we also return to some areas with remarkable regularity. Humans are only slowly beginning to understand that our movements are not random. We may range across whole ocean basins and then appear again near places where we were first seen years earlier.

How I feed

We are top visual predators of the open ocean. We search constantly for prey with our large eyes and speed, and when an opportunity comes, we attack with shocking violence. Shoals of baitfish are especially vulnerable to us, but we will also take larger fish and squid whenever the chance presents itself.

Our bodies, our bills, our eyesight, and our sheer speed all work together. We are not scavengers and not timid pickers. We are hunters built for pursuit, surprise, and impact.

From Egg to Ocean Wanderer

Female blue marlin can spawn several times per year, and each large fish can lay around seven million eggs at each spawning, each egg being about 1 mm in diameter. It is not known what proportion of our species spawns near Portugal or how many other spawning grounds exist, but the result must be many millions, or indeed billions, of tiny planktonic blue marlin floating among and feeding on other planktonic organisms.

Drifting young and astonishing growth

Our young drift with the ocean currents for months, but they grow very rapidly indeed, and larval fish growth of up to 16 mm (0.63 in.) in one day has been recorded. As youngsters, nearly all our planktonic associates die or are eaten. Mortality rates are incredibly high, thank goodness for the amazing fecundity of our ladies.

Blue marlin can reach maturity in between two to four years and at sizes of from 35 to 44 kilograms (77–97 lbs.) in males and 47 to 61 kilograms (104–134 lbs.) in females, to begin the life cycle again.

Lifespan and natural enemies

Female blue marlin are known to live for at least 27 years, while we males live shorter lives and probably die at around 18 years. During this time, as adults, we have few natural enemies except occasionally orcas or large sharks and, of course, man.

I was born in the warm waters off Portugal over ten years ago and so am now in my prime, but also rapidly heading towards the end of my life. That is the way of our kind: a spectacular beginning, a dangerous youth, a powerful adulthood, and then, if we are lucky enough to avoid hooks and lines, a comparatively short old age.

Humans, Hooks, and Fishing Pressure

Because we are such a popular species for sport and commerce, we are under extreme fishing pressure in many parts of the world, including off the Portuguese coast, to which many of us travel each June or July to spawn. The International Union for the Conservation of Nature regards us as threatened due to people targeting us where we congregate to spawn, and also in places like the Caribbean Sea, where long-liners from Cuba, Japan, and elsewhere kill thousands of us annually.

We are also killed as bycatch in other fisheries, such as various forms of tuna fishing in many parts of the world.

The sportfishing paradox

On a happier note, however, any billfish caught within 200 kilometers (124 miles) of the USA coastline must, by law, be released. Unfortunately, we often fight so well that we are exhausted when we are brought to a boat after a long, strong fight, and the delays during photographing and measuring can often result in us succumbing to fatigue.

In past decades many tropical sport fishing destinations erected gabions where large billfish would be hung for the standard photograph of people standing below and beside huge, very dead billfish. In many areas these have been removed, and in most sport fishing competitions billfish may not be boated. Photographs and measurements of the fish in the water are now seen as adequate proof of size and capture.

How humans should release me

So long as stainless steel hooks or leaders are not used, the line to a deeply embedded hook can be cut and then the hook will usually either be thrown from the mouth or ingested and then digested by our strong stomach juices. A billfish brought to a boat can often be resuscitated by gently holding it beside the boat while moving slowly forward, forcing water through the gills. A few extra minutes spent resuscitating a marlin can easily and markedly improve its chances of recovery.

In many areas of the world sport fishers do their best to release a large proportion of billfish, but great care is needed to avoid damage and, sadly, often only a small proportion of tagged and released billfish are ever seen again.

What Science Is Learning About Me

Despite this low recovery rate of tagged fish, some amazing information has already come to light. One of the longest-distance recoveries was from an Atlantic blue marlin tagged off the Delaware coast. It was caught again off the island of Mauritius, in the Indian Ocean, a distance of over 9,000 kilometers (5,592 miles).

Other tagged marlin have been recovered, sometimes many years later, near the site of first capture, but this does not necessarily mean the fish spent its whole life in the area. It might return to specific places routinely.

Tagged, tracked, and followed by satellite

Many billfish are now being tagged with equipment that can be followed by satellite and, slowly, a much better idea of marlin movements, numbers, and distribution is becoming clear. Tagging fish also gives excellent and useful insights into growth and recapture rates, which are very important parameters in terms of mankind trying to manage our populations and fisheries wisely.

I was one of the very lucky ones to be caught by scientists off Florida, landed quickly and carefully, and then fitted with a transmitter before I was resuscitated and released. Now, as I move around and undergo my migrations, I send a constant flow of important information back to the scientists.

My Future, and Yours

Our species has been hard hit by man’s sport and commercial fishing, but it can, or could, rebound if our spawning areas are protected, commercial fishing is controlled, and careful catch and release is practised.

I have seen many colleagues dead or dying attached to impersonal long-lines, waiting to be hauled in and frozen by commercial fishing operators. I have seen friends take baits only to be hauled to a boat, then landed and never seen again. Yet I have also seen humans change. Some now measure us in the water instead of hanging us dead. Some cut the line instead of insisting on a perfect photograph. Some fit a tag, revive us, and let us go.

Hopefully, the information I now send back will help the scientists learn more about me and us and, in turn, that knowledge can be used to improve the future for the Atlantic blue marlin as well as the prospects of the various fisheries.

For I am not merely a trophy, nor merely a source of flesh. I am one of the great wanderers of the open ocean, and if humans are wise enough to let enough of us live, I will continue to bring awe, livelihood, and wildness to the seas for generations to come.

Next in “Life History of a Fish”

Life History of a Fish: Redfish (Red Drum)

I am bronze-backed, copper-sided, strong-tailed, marsh-bred, and guided by moving water more faithfully than many humans are guided by clocks. In much of the American South and Gulf Coast, I am not merely a fish. I am a tradition, an obsession, a first serious inshore target for many anglers, and, for some, the fish that turns casual fishing into a lifelong disease. I belong to the drum family, the Sciaenidae, and if you have ever heard one of us croak, grunt, or thump in shallow water, you already understand part of my story. Scientists call me Sciaenops ocellatus, but for most anglers I am the red drum, or simply redfish. CONTINUE READING