Offshore Pelagics: Tunas, Dolphin and Wahoo Occurring in all tropical, subtropical floating algae which drifts in patches frigate mackerel, Auxis thazard; bullet and temperate oceans of the world, and occurs in large rafts offshore along mackerel, Auxiz rochchei) and five tunas, dolphin and wahoo are one of the warm waters of the Gulf Stream. tunas (albacore,Thunnus alalunga; the fastest swimming groups of fish in Tuna and other highly migratory blackfin, Thunnus atlanticus; bluefin, the sea and one of the most highly pelagic species (swordfish, sharks, Thunnus thynnus; bigeye, Thunnus prized by both recreational and com- dolphin) are taken commercially by a obesus; and yellowfin, Thunnus mercial fishermen for their excellent variety of fishing gears including purse food quality. seines, longlines, drift gill nets, rods and The swimming and fighting strength reels, hand lines and harpoons. In of these fish, when taken by rod and 1996, 28,900 metric tons of tuna were reel, has resulted in their being con- landed by United States Fishermen. sidered top game species by recrea- The commercial harvest of these fish tional fishermen, second only to the off South Carolina and throughout the bigger and more acrobatic billfishes Atlantic is primarily by pelagic longline Little Tunny (blue and white marlin and sailfish). vessels. These vessels fish a line up to Tunas, dolphin and wahoo occur 40 miles long with thousands of baited albacares). Although there is a tremen- throughout the year in warm, cobalt- hooks. Historically, tuna have been the dous variation in adult size, all have a blue water of the Gulf Stream 35 to 75 primary target of these vessels which football-shaped body and a rigid, miles off South Carolina’s coast. During take hundreds of metric tons annually powerful tail, both important in the early spring and summer these fish and in recent years have overfished increasing swimming efficiency. follow warm ocean currents into bluefin. Adult little tunas range from the 2- shallow water 20 to 25 miles offshore. In 1969, 24 countries which fish in pound bullet mackerel to the 40- Pelagic fishes swim and feed in the the Atlantic Ocean, including the pound skipjack tuna. Mature tunas upper portion of the water column. United States, established the Tunas, dolphin and wahoo feed near International Commission for the the top of the pelagic food chain, Conservation of Atlantic Tunas (ICCAT) preying on smaller fish, squid, which is charged with managing all crustaceans and other invertebrates Atlantic highly migratory species, often associated with sargassum including bluefin tuna. Unfortunately, seaweed. Built for speed, these fish bluefin tuna populations and several travel great distances often in schools other highly migratory pelagic stocks according to size. Schooling probably have continued to decline in the protects small fish from predators. western Atlantic, despited the actions Larger tuna, dolphin and wahoo of ICCAT. generally lead a more solitary existence. How these open water species navigate within the vast pelagic environment of the world’s ocean Tunas remains a mystery. Most pelagic fish tend to aggregate Ten tuna species inhabit Atlantic near floating objects such as logs, buoys waters off South Carolina: five little or debris. Whereas tuna are generally tunas (little tunny, Euthynnus an open water species, dolphin and alletteratus; skipjack tuna, Katsuwonus wahoo frequent sargassum,a surface- pelamis; Atlantic bonito, Sarda sarda; begin at 20 pounds (blackfin tuna) and flecks. The magnificent color of incredible growth rates. Two dolphin with the bluefin being the a living fish, which has a lighted or weighing approximately 1 ½ pounds heavyweight of the group reaching glowing appearance, quickly fades were placed in a Florida aquarium nearly 1,500 pounds. with death to a rather uniform, and reportedly grew to 32 and 37 Despite the wide variation in adult unimpressive dark silvery-yellow pounds in seven months. Another sizes, all tunas begin life at the same color. one-pound dolphin, reared in a size and in much the same manner. Dolphin males and females are Miami sea aquarium, grew to 36 Tunas disperse their buoyant eggs, easily distinguished. Males, the pounds in eight months. which are about one millimeter in larger of which are called bull Dolphin not only have a wide range size, into the open sea. A single blue- dolphin, have a pronounced vertical of prey, but also have numerous fin tuna may produce in excess of 25 predators. Dolphin have been taken million eggs per spawn. After drifting from the stomachs of swordfish, in warm ocean currents for up to sailfish, blue and white marlin, three days, young tuna eggs hatch. yellowfin tuna, albacore tuna and Beginning with food within the larger dolphin. Dolphin reach sexual yoke sac, tuna gradually change their maturity as small as 14 inches in diet from the smallest members of the length and spawning may occur year- planktonic community, to larval round. Dolphin spawned in one Dolphin crustaceans and fish, to small fish season may grow, reach sexual such as anchovies, sardines, herrings maturity and spawn in that season, a and squid. As tuna become larger, forehead giving the head a very box- period of just a few months. they seek larger and larger prey. like appearance. Female dolphin Little is currently known about the Feeding constantly, tunas grow have a more sloping, typical fish-like condition of Atlantic dolphin stocks. quickly. Yellowfin tuna may reach head and are referred to as cows. The In Japan, China and other areas of the more that 140 pounds in four years name “dolphin” confuses these fish Pacific, “mahi-mahi” has historically and bluefin, which may live 20 years, with the mammal commonly called been an important food fish. generally weigh more than 700 a dolphin or a porpoise. On most Commercial harvest of dolphin in the pounds by their 14th year. restaurant menus, dolphin is better Atlantic, particularly off the known by its Hawaiian name, “mahi- continental United States is relatively mahi.” small but has increased during the Dolphin are cannibalistic and past few years. Most dolphin taken voracious, feeding primarily on fish, recreationally off the South Carolina crustaceans and squid. Growth is coast are either caught by anglers extremely rapid, with one-year old specifically targeting small school fish averaging 13 pounds, two-year dolphin, or taken incidentally by old 27 pounds, three-year old 55 offshore anglers trolling for blue pounds, and four-year old reaching marlin and other billfish. These latter 75 pounds. fish are generally larger, more solitary Dolphin Aquarium-raised fish have shown dolphin. Dolphin occur in all tropical and subtropical oceans of the world. Whereas the smaller pompano dolphin is primarily an oceanic fish, the common dolphin frequently enters coastal waters. The range of the common dolphin, Coryphaena hippurus, in the western Atlantic is from George’s Bank, Nova Scotia, to Rio de Janeiro, Argentina. Dolphin are prevalent in the Gulf of Mexico and throughout the Caribbean Sea. Not only one of the fastest swimming and best tasting fish in the sea, the common dolphin is one of the most beautiful. The living fish displays a bright, iridescent blue and green upper body and the lower body usually shines brilliant yellow with bright blue and green spots, streaks caught by recreational fishermen and the concept that our oceans’ as by-catch by commercial tuna and resources are limitless and can pro- Wahoo dolphin vessels. vide an endless bounty of seafood. The wahoo’s rapid growth rate, The increasing number and size of The wahoo, Acanthocybium great speed and large teeth all are ocean-going fishing vessels and the solandri, with an elongated cylin- indicative of a top level predator. development of sophisticated elec- drical-shaped body built for speed, Wahoo consume smaller bullet and tronic devices to locate and track is one of the fastest fish in the sea. frigate tuna, king and Spanish mack- marine fish throughout all the world’s Unlike the dolphin’s brilliant blues, erels as well as jacks, butterfish, oceans has clearly demonstrated that greens and yellows, with every fish flying fish and herrings. After their we now have the capacity and ability portraying individual markings, the first year of life, wahoo average about to overfish and deplete the ocean’s wahoo is uniformly colored with dark 3 ½ feet and weigh around 15 natural resources. pounds. Two-year old fish average Bluefin tuna in the 1960’s about 35 pounds. Most wahoo taken accounted for as much as 80 percent off the Carolinas are less than four of the domestic tuna landings in the years old, but occasionally older and western Atlantic. Today this species larger fish are taken. accounts for less than 10 percent. Bluefin tuna breeding populations declined 90 percent between 1975 and 1992. Other highly prized marine fish, such as swordfish, blue and white marlin, several species of sharks and many other marine fish also are currently being overfished. Conservation The realization that ocean fishery resources are finite and their capacity Dolphin, wahoo and most tunas, to be harvested has been reached or especially yellowfin, are delicious exceeded, has and will result in grilled, boiled or baked. In the past, increasing conflicts both between offshore fishermen trolling for billfish nations and various domestic user often caught these fish in abundance groups. Recent actions by Inter- whenever available. national Commission for the Conser- The establishment of the Blue vation of Atlantic Tunas to strengthen Water Conservation Award within the its ability to penalize countries which Wahoos have uniformally dark iridescent Governor’s Cup Billfishing Series do not comply with fishery manage- vertical bands on their sides. however, has encouraged the tag and ment measures should help with release of these species.