Yellowfin tuna is an abundant tropical tuna, found throughout the warmer reaches of the Atlantic, Pacific and Indian oceans. Yellowfin tuna are considered a single species in all oceans. However, the relationships between distinct seasonal aggregations of yellowfin within ocean basins are not well described. In the western Atlantic Ocean, fisheries have developed to target aggregations of yellowfin tuna in the Gulf of Mexico, Caribbean Sea, and along the Continental Shelf and slope waters from Hatteras to Cape Cod. Much larger harvests occur at fishing grounds in the east Atlantic. Yellowfin are exposed to fisheries in Massachusetts only off the south side of Cape Cod, where seasonal warming and Gulf Stream influences allow yellowfin to range over the Continental Shelf to forage during the summer.
Like the other tunas, yellowfin are well known for their physical beauty and powerful swimming. The similar appearance of tunas can lead to some confusion over identification. The bluefin, albacore, yellowfin, and bigeye tuna all have a streamline, "football" shape with darker coloration dorsally and silvery colors on the side. In the yellowfin, the dorsal surface is dark blue and can appear brownish when in the water. True to name, the yellowfin can have much yellow in their fins and shiny, golden yellow along their sides. Coloration alone won't allow you to separate these tunas. A key feature to use at sea is the length of the pectoral fin. The yellowfin pectoral fin reaches the beginning of the second dorsal fin. The albacore pectoral fin always goes beyond the start of the second dorsal and the bluefin pectoral fin never reaches the second dorsal fin. The combination of color and pectoral fin size should suffice in most cases, although in small yellowfin, a combination of the above and gill raker counts (27-33) and presence of a smooth liver may be needed for a positive identification. Another thing to keep in mind is that only bluefin tuna occur in the Gulf of Maine.
Yellowfin tuna are even faster growing than bluefin tuna, but do not reach the large size of their giant cousin. The all-tackle record is a 388 lb. yellowfin tuna caught in Mexico in 1977. On the east coast, yellowfin tuna over 200 lbs. are uncommon. After one year of life, yellowfin are 8-10 pounds. Age-2 yellowfin are about 35 lbs. and age-3 about 75 pounds. A four year old yellowfin averages about 130 lbs. which is a little less than twice that expected of age-4 bluefin tuna. Most of the yellowfin we see on the Continental Shelf each summer are similar in size and typically age-2 or age-3. For reasons not well understood, age-1 are not common and absent in most years on the east coast. Age 4-6 yellowfin have become less common in recent years, a likely response to fishing mortality.
Similar to bluefin tuna, yellowfin tuna's circulatory system acts to retain metabolic heat. This warms their bodies above ambient temperature and allows them to process food and transport oxygen more efficiently. Their ability to stay warm does not match the near warm-blooded bluefin tuna, and as a result, their migration range is more limited by water temperature. The bulk of the population is found at oceanic habitats within 20º latitude of the equator and typically in waters at least 64 ºF. Water temperatures of 68 ºF or higher are often associated with higher catch rates. Their sensitivity to cooler temperatures also limits vertical movements to the relatively thin layer between the thermocline and surface.
While most of the Atlantic yellowfin tuna population is found not too far from the equator, the warm Gulf Stream allows fish to stray north on the west side of the ocean. There appears to be some allegiance among yellowfin tuna in the western North Atlantic Ocean, although there is not enough genetic or migration data to suggest there is a separate stock. During the winter, an aggregation of yellowfin tuna can be found associated with the Gulf Stream running off Cape Hatteras and east of the Continental Shelf slope for several hundred miles. With the warming of summer, some of these fish seem to slip west of the Gulf Stream to forage in the canyons of the Continental Shelf slope and during the warmest months fan out over the shelf to forage along water temperature edges. We actually know little about how these fish interact with yellowfin found in the Caribbean Sea, Gulf of Mexico and east Atlantic. We do know that water temperature limits their progress north. No yellowfin have been caught on the Continental Shelf above Nantucket Shoals and the slope canyons off of Georges Bank and Nova Scotia mark the northern limit off the shelf.
The recent colonization of yellowfin tuna to the Continental Shelf south of New England in the 1970s and accumulating evidence of the influence of global warming on marine habitats raises an enticing question for scientists and anglers to consider as we begin the 21st century. Will yellowfin tuna make the turn around Cape Cod and soon become a seasonal predator in the Gulf of Maine? It has not been documented so far. Nantucket Shoals and the Great South Channel act as a thermal barrier and typical summer Gulf of Maine water temperatures are thought to be too cool for yellowfin.
But, they come close enough now to enter the Gulf on a day-trip and would like the food. And it would certainly be a welcome visit.
Yellowfin tuna have been exploited at high levels for decades in the Atlantic Ocean, however, the harvest appears to be near sustainable yields. Some of this good fortune may come from their prolific biology. Yellowfin tuna grow very fast and reach sexual maturity at age-2 or age-3. Age-2 and age-3 yellowfin can produce several million eggs, and a yellowfin reaching age-4 can produce over eight million eggs and has a narrowing list of predators. This natural history provides good opportunity for successful year classes to come along. The primary spawning grounds in the Atlantic is thought to be the Gulf of Guinea and some spawning occurs in the Gulf of Mexico. Yellowfin cohorts tend to stick together, with tight size ranges found in schools. The age-2 and age-3 yellowfin we see spilling over the Continental Shelf each season are seeking large concentrations of pelagic prey; and typically feed on sand lance, squid, mackerel, and butterfish.
Fisheries for yellowfin tuna in the western North Atlantic Ocean have developed fairly recently. The first recorded catch in the western North Atlantic Ocean came in 1949. From 1949 to 1956, a federal research vessel caught five yellowfin while trolling off the edge of the Continental Shelf. Japanese longline fleets began targeting yellowfin in the Atlantic in 1955, primarily off of South America. Commercial harvest in the U.S. began with purse seine catches in the 1960s, followed by longline activity in the 1970s. Purse seine have been remained sporadic, occasionally reaching 1,000 mt, while the longline fishery developed into the primary harvesting sector for yellowfin tuna in the west Atlantic. Recreational catches of yellowfin tuna began in the 1970s as rod and reel fishermen began picking up yellowfin on the Continental Shelf while targeting other pelagics. Yellowfin tuna soon became a principal target for offshore recreational fleets on the east coast. The rise in importance of yellowfin tuna to east coast fisheries is dramatic. In the 1950s and 1960s, yellowfin tuna was nearly unknown to longline and rod and reel fisheries on the east coast, and since the mid-1980s it has become the dominant tuna species in terms of landings and has generated tremendous economic benefits. As important as yellowfin catches are to the U.S., they are greatly exceeded by the Atlantic-wide harvest of which the U.S. contributes less than five percent.
Yellowfin tuna in the Atlantic Ocean are managed by the International Commission for the Conservation of Altantic Tunas (ICCAT). Yellowfin tuna fisheries under ICCAT do not presently have the detailed country-based quota systems found for Atlantic bluefin tuna. Stock assessments to date have determined that yellowfin tuna are fully exploited in the Atlantic with harvest levels near maximum sustainable yield. Yellowfin tuna management in the Atlantic has primarily been limited to attempts to cap fishing mortality with minimum sizes and restrictions to fishing practices. Despite the determination that Atlantic yellowfin tuna are not overfished, concerns are growing over increasing catches, especially by longline fleets that are making unregulated harvests in the Atlantic outside the authority of ICCAT. The National Marine Fisheries Service is responsible to implement ICCAT regulations and manage domestic fisheries for yellowfin tuna. A minimum size of 27 inches (curved fork length) is currently in place for all U.S. Atlantic fisheries. For permit requirements and regulations contact NMFS at http://www.nmfspermits.com or (888)-872-8862.
Both the recreational and commercial fisheries for yellowfin tuna are regulated by the National Marine Fisheries Service (NMFS). Click here for more information, or call 1-888-USA-TUNA.
Yellowfin tuna are one of the most challenging species to catch with a rod and reel off the coast of Massachusetts. Their large size and high capacity for exercise can result in broken tackle if you are poorly prepared. Yellowfin are usually targeted along the Continental Shelf south of Martha's Vineyard where seasonal conditions create an exciting fishery for pelagic tunas, sharks and marlin. Boats typically need to run offshore at least 20 miles to find the right temperature edges for attracting yellowfin tuna. Trolling and chumming are the primary methods used by anglers. Trolling involves creating a flashy presentation of multiple lures trolled in the boat wake while moving along at 7-8 nautical miles per hour. Single hook lures with plastic skirts are a common offering and chains or spreader bars of lures are an option to increase the visual attraction. Green is a popular color for yellowfin tuna. The idea is to have a pattern of lures that splash, wiggle and sparkle enough to trick the fish into thinking it is attacking a group of agitated baitfish. Chumming involves introducing a baited hook to yellowfin tuna while the boat is drifting or anchored. Cut pieces of butterfish or silver hake are common baits, and small pieces of the bait are deliberately tossed in the water around the baited hook to attract tuna.
Both methods use similar tackle. Since yellowfin typically range between 30-80 pounds in this fishery, you most often see high quality 30, 50, or 80 pound-class reels and rods and line used. Yellowfin that exceed 100 pounds are matched well with the 80 pound class gear. Lighter tackle can be used and is gaining popularity, but you better have time on your hands if you want to land a 150 lb. yellowfin tuna with 30 pound class tackle.
Once hooked, rods are taken from rod holders and transferred to the angler wearing a gimbal belt and/or back harness. This sets up a "stand-up" fish fighting technique that can quickly fatigue the inexperienced angler faced with a large tuna. The excitement generated in the cockpit as multiple yellowfin tuna strike and rip line off the reels has to be a highlight of sportfishing opportunities off the coast of Massachusetts.
Tunas were built to get away, and are not that great at playing hurt. If you plan to release your catch, keep the fish in the water if possible while you carefully remove the hook. Avoid bruising or cutting the tuna during boatside handling If the tuna is fatigued, swim the fish along for a few minutes while the boat is in gear to allow the fish to "catch its breath" (release carbon dioxide and make up oxygen debt). If you plan to boat the tuna, then bleed and chill the fish as soon as possible. Fresh yellowfin is a delight to eat and a 40 pound fish can feed plenty of people. Yellowfin eaten raw doesn't have the premier reputation of bluefin tuna sashimi, but don't pass it up if you like sashimi. And marinated yellowfin steaks on the grill are thought by some to be best among the large pelagics.
Both the recreational and commercial fisheries for Yellowfin tuna are regulated by the National Marine Fisheries Service. Click here for more information, or call 1-888-USA-TUNA.