Indo-Pacific Blue Marlin
Category: High Risk
THE sight of an angry blue marlin, with its pectoral fins lit up, charging at a lure bubbling away close to the transom is indeed one to remember and will haunt your dreams for years to come. If everything goes to plan there will be a crashing strike followed a second or so later by a screaming reel. With heart pumping and adrenalin screaming up to levels not previously experienced, you wrestle the rod from the side deck with shaking hands and strike the fish. Perhaps an unnecessary act, given the force with which it hit the lure, but it’s an angler’s reflex action more than anything.
Marlin are considered by many anglers to be the finest sporting fish in the sea. Immortalised by writers like Ernest Hemingway and Zane Grey, marlin have a place in fishing folklore all of their own – and blue marlin are generally considered the toughest of all the marlins. They grow big, they’re aggressive, they jump, dive deep, pull hard and are revered accordingly by many thousands of anglers worldwide.
Happily these days very few anglers in Australia kill blue marlin, so most are released. The NSW Fisheries Department, in conjunction with the Australian Game Fishing Association, has had a tagging program in place for many years to try to find out more about the movement of these great fish. Other global tagging programs, such as the one run by The Billfish Foundation, also collect some fascinating information about the movements of blue marlin.
Blue marlin are frequently confused with black marlin, especially when the fish are under 100 kilos in weight. However, the pectoral fin on a blue folds back when pushed by hand whereas the black’s remains rigid. The dorsal fin on a blue is also higher than that of a black, but this tends to be more obvious on bigger fish. Blue marlin do have stripes too, which may cause confusion with striped marlin at times. But these stripes fade very quickly when a blue is stressed or dead.
The world record stands at 624 kilos taken in Hawaii, and the Australian record is 452.2 kilos for a blue caught at Batemans Bay in NSW. In WA the biggest blue recorded was taken by the late Sir Garrick Agnew off Rottnest and weighed 319 kilos. Most blue marlin are caught near the southern limit of their range in the waters off Rottnest, where a good blue is 180-200kg and a big fish 250kg-plus. The biggest fish are always females as males only grow to around 170kg (though both sexes have a similar lifespan).
Blue marlin roam the tropical and sub-tropical waters of the Indian and Pacific oceans, ranging northwards from 34deg south off WA. They are mostly found in water deeper than 100 metres and although they prefer water temperatures of 24deg or more they can tolerate temperatures down to 21deg.
In recent years satellite tracking has shown that blue marlin spend most of their time in the surface layer, above the thermocline. It is assumed that the Perth blue marlin fishery receives an influx of fish each year. This conclusion is based upon the fact that each year the fish are in the same size range, and year class, as previous years.
One of the longest distances travelled by a tagged blue marlin to date was recorded for a fish tagged of NSW in the Pacific Ocean and recaptured off Ceylon in the Indian Ocean. That’s probably good justification for using the words Indo-Pacific in its name!
Breeding and migration
Unfortunately, as with many highly valued recreational species, we know very little about the breeding habits of blue marlin although their larvae has been found off north-western Australia between October and March. But it is not known if the species actually spawns in WA waters.
The size of mature female blues varies enormously but males and females mature at 3-4 years (when males are around 80kg). The Leeuwin Current plays a big part in bringing blue marlin in close to the Continental Shelf 200m line, as it frequently holds small tuna and mackerel bait. Even oceanic travellers will stay if the fishing’s good.
Recreational anglers take very few blue marlin these days, preferring to photograph, tag and release them. There would probably not have been more than a handful of blues weighed in the last five years along the entire WA coast. The largest impact is certainly as bycatch of the Australian longline fleet operating within Australia’s 200nm limit, and also of the longline fleets from a dozen nations operating on the Indian Ocean high seas.
In 1994 the Commonwealth Government, which has final responsibility for managing blue marlin stocks in Australia, protected them from commercial exploitation. However, catch data to indicate the success or otherwise of this move is unfortunately incomplete.
Back in 1998 a CSIRO Billfish Assessment Group reported that blue marlin numbers had declined significantly in the Indian Ocean since the Japanese started longlining years previously. It is unlikely that stocks have recovered since then, although the West Australian Game Fishing Association and the Game Fishing Association of Australia are working hard to stabilise and reverse this trend.
Tackle and bait
There are three main methods for catching blue marlin – live baits, dead baits and lures – but these days over 95 per cent of anglers use skirted surface trolling lures. Fishing lures is easier, cleaner and can be carried out successfully even by relatively inexperienced crews.
In the early days of the blue marlin fishery off the west coast, 60kg and 37kg outfits were the norm but with increased knowledge and gear improvements, 24kg outfits are more commonly seen adorning the back decks of successful marlin boats. However, a word of caution for beginners: blues are very powerful fish and are best tackled on 37kg when you’re starting off. When a blue dives it can empty 500m of line very quickly indeed and bigger fish are almost impossible to bring up from the bottom on 24kg. The result is all to frequently a bust off.
Marlin lures are attractive and expensive pieces of fishing jewellery rarely lent or given to other crews. A hot marlin lure with scars and scratches all over it is highly prized and run frequently. Australian Pakula lures are one of the most successful in use around the coast. Overseas lures such as Joe Yee, Marlin Magic and Black Bart are also popular.
I like to run a pattern of at least four, sometimes five, lures staggered in the wake of the boat to avoid tangles. One big lure, fished straight off the rod tip, is always close to one corner of the transom and consistently takes big fish. Another lure is also run off the rod tip on the other corner, but bit farther back, and two lines clipped to outriggers complete the normal lure pattern.
There appears to be no foolproof lure colour selection method although many anglers try to pick lures that resemble the available bait colours. Having said that, Pakula’s Lumo colours have done really well – perhaps they look like a squid travelling at warp speed!
The common adage that if you find bait you will find blue marlin is fairly accurate. Blues love striped tuna and slimey mackerel and can often be found not far away from them. Blues will also hang around pilchard and scaly mackerel schools. When you find bait don’t troll lures through it – rather, set up a trolling pattern around the edge so that you don’t put the bait down (and also so the marlin can see your lures).
Trolling along current temperature lines can turn up some fish too, as can FADs and other floating objects. Look for birds as a tell-tale sign of bait, and if all else fails troll the 200m dropoffs until you find a fish. I fish a strike drag of one-third of the line class I’m using. This often results in the blue hooking itself.
Handling blue marlin boatside is potentially dangerous and all care should be taken to protect the crew and of course the fish. Swim tired fish by holding the bill just below the surface and moving slowly forward, in gear, to flush water over the gills. Even very tired fish can recover quite quickly if handled properly. As I said, blues can provide the experience of a lifetime; just make sure it’s not the last one for you or the fish.
Kailola, Williams, Stewart, Reichelt, McNee and Grieve Australian Fisheries Resources 1993.Hutchins and Swainston Sea Fishes of Southern Australia 1986.