Tags Fish Guide


Tags Fish Guide
WITHOUT doubt, broadbill swordfish are an iconic oceanic species. They are one of the fastest, most powerful fish in the sea. But they are not easy to catch and in Western Australia only a handful of broadbill have ever been taken by rod and reel. But talking to people who have caught them, and lost some of them too, it is apparent that they are one of, if not the strongest fish in the ocean.

They are also a fish of mystery as they live in deep oceanic waters well away from the coast. Very few anglers have ever seen a broadbill during daylight hours in Western Australia, let alone hooked or landed one. The broadbill is the epitome of power and their body shape simply confirms this. Big heavy shoulders leading back towards a big lunate tail, with a heavy wrist that carries a single large keel on each side. Its large eye allows it to hunt in the dark, at depths of up to 650 metres, and its physiology is such that it can swim up to the surface from these depths without suffering barotrauma.

The broad, flat bill — from which it derives its name — is approximately one third of the body length of a mature adult, and it is a fearsome weapon indeed. Broadbill are one of the few creatures in the ocean that will attack blue pointer sharks, which inhabit the same territory. Indeed one broadbill was filmed attacking a submersible! No wonder anglers love them.

Broadbill swordfish are a prime target of commercial longline fleets both in Australian waters and on the high seas. Europeans in particular love them, and broadbill are very popular in countries around the Mediterranean. So popular, and for so long, that the commercial fishing pressure in the Mediterranean is believed to have actually brought about a change in the size of maturity of this species. While broadbill swim in the Indian Ocean many anglers will aspire to catch them, some will actually get to try, but far fewer will actually achieve the dream of landing a big broadbill swordfish.

Broadbill swordfish, as the name suggests, carry a large broad, sword-like, bill which is around one-third of the overall length of the fish. They are a blackish-brown, with a hint of purple, on their backs fading to light brown or cream on the belly. Adults have no teeth or scales. They have two widely separated dorsal fins, no pelvic fins at all and a large keel on each side of the wrist of the tail.

Broadbill can grow up to 540 kilos in weight, but a 350kg fish is a really big one in West Australian waters, with a good fish going 200kg. Having said that, the few broadbill that have been caught in WA have all been under 100 kilos.

Broadbill are widely distributed throughout WA waters and can tolerate a very large range of water temperatures from 5-27 degrees Celsius. They are found beyond the edge of the Continental Shelf where they congregate around deep seamounts and canyons.

Breeding and migration
Spawning takes place in the upper layers of the ocean and mainly occurs in water temperatures of 24 degrees Celsius and above. Adult broadbill do not aggregate to spawn but breed as a pair. Their pelagic eggs drift around in the ocean currents and when the larvae hatch they tend to stay within a few metres of the surface, where they feed on other fish larvae once they attain 10mm in length. Juvenile broadbill have been recovered at the Rottnest Trench, off Perth, during summer and this indicates, allowing for the strength of the Leeuwin Current, that some breeding occurs south of the Abrolhos.

Broadbill take about five to six years to mature at which point they weigh around 70 kilos. After they reach two years, females grow much more rapidly than males and ultimately achieve a much larger size. Very little is know about the large-scale movement of broadbill, but it is known that they congregate around deep seamounts and canyons.

It is thought that, as swordfish are primarily a warm water species, its major migrations would most likely be towards temperate waters in summer for feeding and then back into warmer water in winter for spawning. It is known from satellite tagging programs that swordfish move into the surface layers of the ocean at night and then move back down to the depths during the day. It is thought by some scientists that this vertical movement may assist in food digestion amongst other things. It may also be that this behaviour assists in helping the fish to recover from the low oxygen and water temperatures in the deeper water.

These vertical movements may occur quite fast and broadbill have to contend with variations in water temperature of up to 19 degrees Celsius. In order to be able to safely undertake these huge variations in temperature the broadbill have various attributes which include a series of blood vessels behind the eye to enable it to operate at optimal temperatures and maintain its acuity.

The biggest single threat to broadbill swordfish is pelagic longlines, both of the relatively new Australian fleet in local waters and the fleets of other nations on the high seas. To illustrate this point, the Japanese longline fleet that fished our waters (inside 200 nautical miles) until the early nineties caught up to 150 tonnes of broadbill whereas the Australian fleet a couple of years ago were taking nearly 2,500 tonnes. This is because the Australian fleet target broadbill very successfully using different fishing gear to the Japanese longliners. The concern is that Australian fisheries experiences, at Mooloolaba in Queensland, have shown that broadbill stocks are very vulnerable to localised depletions and these may well have already occurred in WA waters. Inshore longline closures are looking like the only viable solution to allow recreational anglers to access this icon species.

Tackle and bait
Because broadbill are so strong, I would suggest that 37kg and 60kg game fishing gear is best suited to the task. You will need heavy mono traces and the strongest crimps and swivels you can find when targeting this species. Large tuna circle hooks are preferred by anglers chasing broadbill using baits, but the advent of slow trolling at night has seen the return to popularity of conventional J hooks. Broadbill feed primarily on pelagic fish species like tuna, mahi mahi and flying fish, as well as squid. On the occasions that they move over the Continental Shelf they will feed on mackerel, sardines and sauries. This means there are a range of bait options that can be used for broadbill.

Fishing methods
The old tried and tested internationally accepted way to catch broadbill was to drift at night and set a range of baits at various depths ranging from 20-150m below the surface. Squid, mackerel or small tuna were the preferred baits. Now this method still certainly works, but increasingly anglers are looking to cover more water and adopting slow trolling methods to do this. Slow trolling is carried out at boat idle speed and a whole squid, tuna, or a fresh belly flap, is rigged behind a softhead skirted trolling lure and then set to swim deep using breakaway sinkers or a downrigger. This is the way I would fish because it allows me to fish the structure I have chosen rather than simply drifting at the whim of the current and wind. Importantly too, it allows me to cover more of the ocean to find a broadbill.

The strike of a broadbill is a bit different to what you might expect from such a large and powerful fish. Often it’s a slow clicking of the reel as the fish takes the bait, increasing gradually as the broadbill picks up speed. But a word of caution here; the mouth of a broadbill is quite soft in parts so quite a few fish come unstuck early in the piece leaving anglers shaking, bewildered and wondering what might have been. But if your hook holds the fight from there on I can guarantee the fight will be hard and exciting. They really are very special fish.

References: Australian Fisheries Resources by Kailola, Williams, Stewart, Reichelt, McNee and Grieve. FAO Species Catalogue No. 5, Billfishes of the World by Izumi Nakamura.
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