I'm often asked to make comparisons between black and blue marlin, and which species I prefer to pursue. I usually just tell people that I like both species — a lot — and the bigger the better. But I probably would rather fish where I can get lots of bites on modest-sized fish of any species than only get to see a big one once in a while. However, all that goes out the window if I'm sure of getting a few bites on truly big marlin, which means fish over 1,000 pounds. Monster blues and blacks crank up my adrenal gland.
 
Blues Get Bigger  
Many anglers and crews think that black marlin get bigger than blues, but that's not so. There were four black marlin over 1,500 pounds caught and weighed in Cabo Blanco, Peru, in the early to mid-1950s. The existing men's record of 1,560 pounds and the women's record of 1,525 were caught in 1953 and 1954 respectively. 
 
And although fewer blue marlin have been taken weighing over 1,000 pounds than blacks, blue marlin do not top out in the 1,400- to 1,500-pound size range like blacks do — they keep growing. I know of at least three, probably four, blue marlin that weighed over 1,800 pounds.  
 
The list of monster blue marlin includes two from Hawaii caught on charter boats: Black Bart's 1,649-pound blue out of Kona and the Coreen C's 1,805-pounder out of Honolulu. (Neither appears in the record book because of IGFA rule infractions.) The latter fish's mount sits on display at the International Marketplace near Waikiki Beach. I've visited this mount and gazed at it in awe many times. It is huge!
 
A local Tahitian fisherman caught a 1,840-pound blue on a handline and weighed it in the market in Papeete. But that fish still didn't look as big as another unweighed fish photographed on the floor of the market in Tahiti with a little boy sitting astride the monster. I saw the dried tails of both fish on the wall of the Hertz Rent A Car agency in Papeete in the late 1960s. The unweighed fish's tail had a much greater span from tip to tip and was much larger in circumference at the base. I think this fish probably weighed over 2,000 pounds.
 
Finally, I know of a receipt from a fish buyer in the Canary Islands recording a fish over 2,000 pounds. It's highly unlikely that the buyer exaggerated the size of a fish he was paying for.
 
It's also interesting to note that while there were 34 granders caught in Peru, there have been over 700 caught in Cairns, and not one hit 1,500 pounds. As captain or mate, I have personally been on the boat for 76 black marlin captures weighing over 1,000 pounds, more than double all the Cabo Blanco fish. That number includes the Aussie record of 1,442 pounds, which replaced a 1,417 caught in the same year, 1973. I knew several of the crew and anglers from Peru, all honest and ethical sportsmen, but I also doubt very much that the Peru record will ever be broken — for some reason, blacks just don't seem to reach that weight in the waters off Cairns. There have been more than twice as many 1,300-pound blacks caught in Cairns as the total number of granders from Peru, and all of them measured out larger than the 1,560-pound all-tackle record.
 
I'm also positive the ones that get away can't be as big as the stories the losers tell. Crews boat very few granders in Cairns these days, preferring to release them, and I would estimate that the average released "grander" in recent years actually weighed about 850 pounds. Too many crews with too little experience have cheapened the truly thrilling experience of releasing a 1,000-pound marlin.
 
Where They Live
Black marlin only live in the Pacific and Indian Oceans. Like sailfish, black marlin commonly move into relatively shallow water, along or near continental shelves or the coastlines of islands within easy reach of sport fishermen. The best known black marlin hot spots lie along shallow reefs off Australia, Mozambique, Panama and the Pacific coasts of several other Central American countries.
 
Blue marlin, on the other hand, circumnavigate the globe, like dolphin fish. And while tagging results show that both blue and black marlin migrate across seas and oceans, blue marlin represent a truly oceanic species with large populations found in the vast, mid-ocean waters. This puts a large number out of range of coastal sport fishermen. 
 
The best blue marlin hot spots, especially for the biggest adult females, are generally the flyspecks on the oceanic charts indicating islands in the middle of the ocean. Other blue marlin fishing grounds occur where deep blue ocean water runs close inshore along continents, often around the canyons carved out eons ago by ancient river systems.

Telling Them Apart
Since all billfish, with the exception of swordfish, have a color pattern with a dark blue to almost black upper body (when alive) and a silver belly with vertical blue lines on their sides, it is sometimes very hard to tell them apart at first glance.
 
Black marlin tend to sport larger heads and massive, club-like bills. On the other hand, blue marlin wield a more slender, rapier-like bill. Both species' bottom and upper jaws (which includes the bill) are covered with rough, raspy, tooth-like "denticles."
 
However, the most easily observed and distinguishing features crews use to separate blues from blacks are the rigid pectoral fins found on all adult black marlin. The bones that form the "pectoral girdle" fuse in adult black marlin. A black marlin over 100 pounds can't fold its pectoral fins back against its body like a blue marlin can. Some say these rigid fins provide lift like an airplane wing, allowing black marlin to cruise at slower speeds without expending a lot of energy.
 
By folding back its pectoral fins, a blue marlin attains a more streamlined shape and a nearly perfect hydrodynamic design. Theoretically, this allows blues to greatly reduce the amount of friction working against their bodies as they move through the water, resulting in much faster speeds.
 
How Fast?
In my opinion, there's no question that blue marlin make faster sprinters than blacks. The first year the IGFA started keeping records for 6-pound we spent several weeks fishing for the new line-class records. We fished from highly maneuverable boats with great anglers, experienced deck crew, an aggressive captain and the best tackle money can buy. We went on to catch records on both blues and blacks.

The greatest difference between the two species came in how we lost the ones we didn't catch. We lost most of the blue marlin in the first couple of minutes. 
 
I use an analogy with horses to compare blue and black marlin. Blue marlin represent the thoroughbreds of the sea; they're extremely fast and could break the line due to the friction their sheer speed imparts to the line trailing behind them. Even with the reel in near free spool and with aggressive boat handling, several blue marlin break the line before completing their first run.
 
In contrast, we rarely lost a black in the first wild bit of running and jumping. When a black eventually settled down and paddled along at a steady pace, we tried to add drag and maneuver in such a way as to get the fish to make the wrong move and come to the top. We usually kept upping the drag until the line broke, since we felt we had a better chance on the blacks by looking for a new fish and trying for a quick knockout in the first few minutes.
 
Blacks are more like the Clydesdales of the marlin family; they pull harder and longer than any fish I've ever caught. And while a draught horse (black) can get up a pretty good gallop, they do not compare with a racehorse (blue) in terms of top-end speed.
 
We use heavier rods and higher drag settings on black marlin in Cairns than anglers and crews use anywhere else in the world. I took my heavy black marlin rods back to Madeira and found them just a bit too heavy for the blues there. You just do not need to use as much drag on blues as you do on blacks. (And by the way, any of you tuna freaks who think tuna pull harder and swim faster than marlin, just remember that both blues and blacks eat tuna for breakfast.)
 
By spinning the boat and chasing marlin, we rarely lose 200 yards of line on the first run — even with boats that can't reach 20 mph. Marlin (and tuna) are magnificent fish, but most folks highly exaggerate their top-end speeds. I sincerely doubt they can exceed 25 mph.