Swordfish Research

Swordfish (Xiphias gladius). Image credit Guy Harvey.

Introduction

Swordfish (Xiphias gladius) is an important resource supporting major fisheries in all oceans of the world. Much of the Pacific catch is taken incidentally in longline fisheries targeting tunas. Recent landings average around 34,000 metric tons. Japan, Taiwan and the U.S. account for about 70% of current reported production, with Mexico, Ecuador and Chile providing the remainder. In the eastern Pacific, swordfish are primarily harvested using longlines, driftnets and hand-held harpoons. Total California swordfish landings peaked in 1985 at 3,500 metric tons valued at 19.2 million dollars.

The California harpoon fishery dates back to the early 1900s and the Tuna Club of Avalon reported the first record of a recreationally caught swordfish in 1909 that weighed 339 pounds. Participation in the harpoon fishery peaked in 1978 with 309 vessels landing 2,700 metric tons before being largely displaced by the more efficient driftnet fishery.

The driftnet fishery proved more cost effective in terms of fuel economy and yielded greater catches than was possible with harpoon gear. Annual landings of driftnet caught swordfish peaked in 1984 at 2,400 metric tons valued at 10.3 million dollars. Regulations enacted in 1985 effectively reduced fishing effort and landings, limited the number of permits, restricted the fishing season and provided several time-area closures aimed at reducing bycatch and interactions with recreational anglers. Driftnet vessels, which numbered 220 in 1985, have decreased due to those regulations and now number about 120 vessels. These fishers ply the waters from the Mexican border to Oregon and off shore to 200 miles.

In 1983, Mexico restricted the use of longlines along their coast by limiting the catch of billfish within 50 miles of their coast. A small fleet of driftnet vessels, based in Ensenada began fishing swordfish in 1986. They operated from Ensenada moving south along the Baja peninsula and generally within 100 miles of the coast. They averaged nearly 450 mt of swordfish between 1986 and 1993. Concerns over bycatch of sport and protected species prompted the Mexican government to issue permits in 2000 allowing these driftnet vessels to convert to longline gear.

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Biology

Swordfish, is the single species within its own family Xiphidae. It is characterized by a long, flat bill in contrast to the smooth, round bill of the marlins. Swordfish are elongate, round bodied, and lack teeth and scales as adults. They reach a maximum size of 14 feet and 1,190 pounds. The International Game Fish Association’sThe previous link is a link to Non-Federal government web site. Click to review NOAA Fisheries disclaimer all tackle angling record is a 1,182-pound fish taken off Chile in 1953.

Swordfish are distributed in tropical, subtropical and temperate waters and tend to concentrate where major ocean currents meet, and along temperature fronts. They inhabit the mixed surface waters where temperatures are greater than 15°C but also can move into water as cool as 5°C for short periods aided by specially adapted brain and eye heat exchange organs.

Areas of greater apparent abundance occur north of Hawaii along the North Pacific transition zone, along the west coasts of the U.S. and Mexico and in the western Pacific, east of Japan. Migration patterns have not been described although tag release and recapture data indicate an eastward movement from the central Pacific, north of Hawaii, toward the U.S. West Coast. Acoustic tracking indicates some diel movement from deeper depths during the daytime and moving into the mixed surface water at night. At times they appear to follow the deep scattering layer, and small prey, as they undertake these vertical movements.

Females grow larger than males, as males over 300 pounds are rare. Females mature at 4 - 5 years of age in northwest Pacific while males mature first at about 3 to 4 years. In the North Pacific, batch spawning occurs in water warmer than 24°C from March to July and year round in the equatorial Pacific. Adult swordfish forage includes pelagic fish including small tuna, dorado, barracuda, flying fish, mackerel as well as benthic species of hake and rockfish. Squid are important when available. Swordfish likely have few predators as adults although juveniles are vulnerable to predation by large pelagic fish.

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Status

The status of swordfish in the Pacific is unclear and assessment results are often conflicting. The most recent assessment suggests swordfish comprise a single, continuous stock throughout the Pacific with areas of high and low abundance. This assumes the population is sufficiently large and mobile enough to prevent depletion. Genetic evidence indicates swordfish off the western coast of the Americas mix with fish from the central and western North Pacific. A second theory suggests the possibly of three or more stocks exist based on areas of high abundance but somewhat continuous over areas of low abundance. Both hypotheses conclude Pacific stock(s) of swordfish are relatively healthy and being fished at levels below maximum sustained yield although recent fishery statistics have not been available.

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Management

Current assessments are based on old and incomplete data. New assessments using updated and standardized fishery statistics are necessary to determine stock condition and to validate existing levels for maximum sustained yield. International conventions are currently being developed and a Federal Management Plan is currently being drafted for highly migratory specie by the Pacific Fishery Management CouncilThe previous link is a link to Non-Federal government web site. Click to review NOAA Fisheries disclaimer to improve reporting of fishery statistics from all fishing nations.

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Last modified: 11/18/2015