Offshore Pelagics: Tunas, Dolphin and Wahoo
Occurring in all tropical, subtropical and temperate oceans of the world, tunas, dolphin and wahoo are one of the fastest swimming groups of fish in the sea and one of the most highly prized by both recreational and commercial fishermen for their excellent food quality.
The swimming and fighting strength of these fish, when taken by rod and reel, has resulted in their being considered top game species by recreational fishermen, second only to the bigger and more acrobatic billfishes (blue and white marlin and sailfish). Tunas, dolphin and wahoo occur throughout the year in warm, cobaltblue water of the Gulf Stream 35 to 75 miles off South Carolina’s coast. During the early spring and summer these fish follow warm ocean currents into shallow water 20 to 25 miles offshore.
Pelagic fishes swim and feed in the upper portion of the water column. Tunas, dolphin and wahoo feed near the top of the pelagic food chain, preying on smaller fish, squid, crustaceans and other invertebrates often associated with sargassum seaweed. Built for speed, these fish travel great distances often in schools according to size. Schooling probably protects small fish from predators. Larger tuna, dolphin and wahoo generally lead a more solitary existence. How these open water species navigate within the vast pelagic environment of the world’s ocean remains a mystery.
Most pelagic fish tend to aggregate near floating objects such as logs, buoys or debris. Whereas tuna are generally an open water species, dolphin and wahoo frequent sargassum,a surfacefloating algae which drifts in patches and occurs in large rafts offshore along the warm waters of the Gulf Stream.
Tuna and other highly migratory pelagic species (swordfish, sharks, dolphin) are taken commercially by a variety of fishing gears including purse seines, longlines, drift gill nets, rods and reels, hand lines and harpoons. In 1996, 28,900 metric tons of tuna were landed by United States Fishermen.
The commercial harvest of these fish off South Carolina and throughout the Atlantic is primarily by pelagic longline vessels. These vessels fish a line up to 40 miles long with thousands of baited hooks. Historically, tuna have been the primary target of these vessels which take hundreds of metric tons annually and in recent years have overfished bluefin.
In 1969, 24 countries which fish in the Atlantic Ocean, including the United States, established the International Commission for the Conservation of Atlantic Tunas (ICCAT) which is charged with managing all Atlantic highly migratory species, including bluefin tuna. Unfortunately, bluefin tuna populations and several other highly migratory pelagic stocks have continued to decline in the western Atlantic, despited the actions of ICCAT.