Seeing seamounts through fishermen’s eyes

A survey carried out by IUCN among fishermen in the Western Pacific region of Tonga, Fiji, Samoa and the Cook islands has given precious insight into the state of seamounts—mountains that rise from the seafloor and support rich biodiversity as well as important fisheries.

Leatherback turtle tangled in longline

The study is part of a project funded by the Global Environmental Facility and implemented by the United Nations Development Programme in partnership with IUCN. The project aims to improve scientific understanding of high seas biodiversity and fisheries, improve high seas resource conservation and management and raise awareness about the importance of seamounts.

It is estimated that there are more than 1 million seamounts in our oceans and 30,000 that are higher than 1,000 m are believed to exist in the Pacific.

Seamount processes and linkages are complex. Currents hitting seamounts are forced upwards, causing localized upwellings which can bring nutrients from the deeper ocean, making the area more productive. This has a flow-on effect, supporting a seamount ecosystem with a high diversity of life. Highly migratory fish such as tuna and billfish aggregate around seamounts, possibly due to this higher productivity, and seamounts are also likely sites for spawning aggregations of a number of species. A number of commercially important bottom fish including snappers, groupers, deep sea trevalla and alfonsino are also a part of the seamount ecosystem.

“While being a productive focus for a significant sector of the fishing industry, seamount ecosystems are also very vulnerable,” says Kelvin Passfield, IUCN’s Marine Programme Officer. “IUCN’s Oceania Regional Office has gathered information from those that know these ecosystems better than most, that is, the fishermen who rely on them for their livelihoods. This has revealed some important information on fishing practices in these unique marine areas as well some knowledge of their biodiversity.”

According to the survey, approximately 40% of all longline fishing in the Western and Central Pacific Ocean is carried out around seamounts and 60% in open seas. The fish caught in seamount areas are mainly yellowfin, skipjack and bigeye tuna, mahi mahi and swordfish.

Apart from the main target species, longline fishermen fishing around seamounts also catch other species, including reef sharks, wahoo, and oilfish, as well as groupers, snappers and turtles.

One of the major issues faced in the Pacific Islands fishery is the vulnerable status of Bigeye tuna. This species is being overfished, and according to the Scientific Committee of the West and Central Pacific Fisheries Commission, a reduction of 30 to 40% in catch is required to prevent the fishery collapsing. One possible way to help achieve this reduction is by reducing the number of juvenile bigeye being caught. Juvenile bigeye tuna are sold to fish canneries for approximately $7 each. If left to grow, each fish would be worth approximately 50 times more if caught as an adult. They would also have had the opportunity to reproduce, help ensure the sustainability of the fishery, and help the people of the Pacific Islands, whose survival so heavily depends on the resources of the ocean.

Seabed mining and possibly bottom trawling could become serious threats to Pacific seamount ecosystems in the near future. Proper management of fishing access and capacity, accompanied by effective communication and broader awareness-raising efforts on sustainable use of these unique marine areas, are necessary to ensure the future of pelagic fisheries that are vital to the economies of the Pacific Islands.

For more information please contact: Kelvin Passfield, IUCN’s Marine Programme Officer

Watch Dr. Alex Rogers revealing some seamounts secrets


Work area: 
Coastal Livelihoods
Fisheries & Aquaculture
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