Habitat characterization, fishery development, and stock structure of swordfish off California

Project Number
Project Date Range
Funding Agency
California Ocean Protection Council (OPC)
Focus Area(s)
Sustainable Fisheries and Aquaculture

This project aimed to improve the essential fishery information and long-term sustainability of the north Pacific swordfish, a valuable West Coast fishery. California is one of the largest consumers of swordfish globally, but increasingly relies on imported swordfish to meet demand. Although currently suppressed, the California swordfish fishery continues to contribute significantly to jobs and economy in the state.  As with most swordfish industries, the California fishery has faced recent challenges that include interactions with protected species, as well as management concerns over the lack of information available regarding stock structure. 

In order to decrease bycatch of protected species, researchers and fishers have been developing new types of gear that can selectively target swordfish during the day in deeper waters where fewer protected species are found. Gear trials have shown that marketable catch remained above 95% with the new deep-set methods. Despite these advancements, managers have until recently lacked fine-scale data on the horizontal and vertical distribution of swordfish over much of the California coast. This project intended to collect such data.

Using Ocean Protection Council funds, PIER’s research team deployed over 150 electronic tags on over 90 different swordfish. Researchers from PIER also worked with two electronic tag manufacturers, Lotek Wireless Ltd and Wildlife Computers, to optimize tag designs specifically for swordfish, a collaboration that has resulted in similar tagging efforts in other ocean basins. Each time a tagged swordfish surfaces to bask, the tags send its geographic position back to researchers. The team also collaborated with the Alvarado Bremer Laboratory at Texas A&M at Galveston to provide researchers with additional genetic evidence that will further the understanding of how swordfish utilize the Pacific.

The tags provided a comprehensive dataset on swordfish movement that spans 2.5 years. The data revealed that individual fish traveled thousands of miles each season: as far south as the equator or as far west as the Island of Kona, Hawaii. But despite the great distances traversed, the fish stayed loyal to their favored foraging grounds in California, returning to the same general locations year after year. Most importantly, though, the data showed that Southern California swordfish, for example, spent significant time in both the Eastern Pacific and Western and Central Pacific management units.

This insight, along with data from previous PIER tagging efforts prompted the International Scientific Committee for Tuna and Tuna-like species in the North Pacific Ocean and the Inter-American Tropical Tuna Commission — the two organizations that manage swordfish stocks in the region — to modify the boundary designations in the North Pacific in 2023. 

Principal Investigators
Chugey Sepulveda
Pfleger Institute of Environmental Research

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