Biological State and Trend
Habitat and Biology
Depth zone: Abyssal ( >1000m). Horizontal distribution: Oceanic. Vertical distribution: Pelagic.
Geographical Distribution
Jurisdictional distribution: Highly migratory
Resource Structure
Considered a single stock: Yes
Swordfish tend to inhabit waters further below the surface during the day than at night, and they tend to inhabit frontal zones. Several of these occur in the eastern Pacific Ocean (EPO), including areas off California and Baja California, off Ecuador, Peru, and Chile, and in the equatorial Pacific. Swordfish tolerate temperatures of about 5° to 27°C, but their optimum range is about 18° to 22°C, and larvae have been found only at temperatures exceeding 24°C.
Swordfish grow in length very rapidly, with both males and the faster-growing females reaching lower-jaw-fork lengths of more than a meter during their first year. Swordfish begin reaching maturity at about two years of age, when they are about 150 to 170 cm in length, and by age four all are mature. They probably spawn more than once per season. For fish greater than 170 cm in length, the proportion of females increases with increasing length.
There is strong evidence that swordfish in the Pacific comprises multiple stocks, especially in the northern EPO. Several specific spawning regions are known, and analyses of fisheries, tagging and genetic data suggest that there is only limited exchange of swordfish between geographical areas, including between the eastern and western, and the northern and southern, Pacific Ocean. As many as six stocks may exist in the PO, but the exact boundaries of these stocks, as well as their exchange rates—for the purposes of stock assessment—is currently uncertain.
Exploitation
Swordfish (
Xiphias gladius) occur throughout the Pacific Ocean (PO) between about 50°N and 50°S. In the Eastern Pacific Ocean (EPO), they are caught mostly by the longline fishery—80% of the catch in weight on average 2009-2018—by distant water fleets of Far East and Western Hemisphere nations. Lesser amounts are taken by drifting gillnets (~20%), mainly in South America, and minimal amounts by other gillnets and harpoons. They are seldom caught in the recreational fishery in the EPO.
The annual longline fishing effort in the north EPO increased from about 43 million hooks in 2007 to about 66 million hooks in 2011. However, the 78 million hooks set in 2018 remains significantly below the 2001-2003 average of 113 million hooks. (Figure G-1)
See also fishery fact sheet:
EPO Tunas and billfishes fishery |
Longline fishing effort (in millions of hooks) in the North EPO for the main longline fleets.  |
Assessment
Overall Assessment Results
A
sex-specific age-structured stock assessment of swordfish in the Pacific Ocean north of the equator from 2007 indicated that, at level of fishing effort of that time 2007, there was negligible risk of the spawning biomass decreasing to less than 40% of its unfished level. The results of a North Pacific swordfish stock assessment for 2002 for the area north of 10°N and west of 140°W (
ISC3/SWO-WG/02/04) indicated that stock biomass has been stable and well above 50% of unexploited levels, indicating that the stock was not overexploited at current levels of fishing effort. In the early 2000’s, the IATTC produced
indicators for swordfish, in five areas of the EPO: two areas north of 10°N, separated at 125°W, a central area between 10°N and 5°S, and two areas south of 5°S, separated at 90°W.
Based on these considerations, and the long period of relatively stable catches that have average 3,231 mt over the past 10 years, swordfish are probably not overfished and overfishing is most likely not occurring in the North EPO (Figure G-2).
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| Figure G-2: Retained catches of swordfish in the North EPO. |
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