Longfin tuna
The albacore (Thunnus alalunga), known also as the longfin tuna, is a species of tuna of the order Scombriformes. It is found in temperate and tropical waters across the globe in the epipelagic and mesopelagic zones. There are six distinct stocks known globally in the Atlantic, Pacific, and Indian oceans, as well as the Mediterranean Sea. The albacore has an elongate, fusiform body with a conical snout, large eyes, and remarkably long pectoral fins. Its body is a deep blue dorsally and shades of silvery white ventrally. Individuals can reach up to 1.4 m (4 ft 7 in) in length.
Albacore are pelagic predators that eat a wide variety of foods, including but not limited to fish, crustaceans, and cephalopods. They are unique among tuna in that their primary food source is cephalopods, with fish making up a much smaller portion of their diet. Reproduction usually occurs from November to February and is oviparous. An adult female can release over two million eggs in a single cycle. Fry (juvenile fish) generally stay near where they were spawned for about a year before moving on. Albacore form schools based on their stage in the life cycle, but also combine with other tuna like the skipjack tuna, yellowfin tuna, and bluefin tuna. Once grown, schools are highly migratory.
The albacore is a very economically important fish and is a target of commercial and recreational fisheries. It was originally the basis for the United States tuna-canning industry and is no less important today, making up significant percentages of the gross domestic products of various Pacific nations. It was listed as Near Threatened by the International Union for Conservation of Nature (IUCN) because of the threat of overfishing but is now Least Concern again. Several stocks were in significant decline and the species' overall population were decreasing but are now recovering thanks to the enforcement of regional fishing quotas.
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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PiscivoresA piscivore is a carnivorous animal that eats primarily fish. Piscivorous is equivalent to the Greek-derived word ichthyophagous. Fish were the die...
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PlanktivoreA planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton. Phytoplankton are usually photosynthet...
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CosmopolitanAnimals with cosmopolitan distribution are those whose range extends across all or most of the world in appropriate habitats. Another aspect of cos...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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PolygynandryPolygynandry is a mating system in which both males and females have multiple mating partners during a breeding season.
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MigratingAnimal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migrati...
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OceanodromousA
starts withThe albacore has a streamlined, fusiform body with a conical snout, large mouth, and big eyes. Its body is dark blue dorsally, shades of silvery white ventrally, and covered by small scales. The pectoral fins begin slightly before the first dorsal fin and extend well beyond the front of the anal fin, usually as far as the second dorsal finlet, often as long as 30% of the fish's total length. Like the fish's body, the fins are dark blue on top, but change to a medium yellow color on the underside. They are markedly shorter in fish under 0.5 m (1 ft 8 in) in length, often resulting in confusion with T. obesus juveniles, which also have long pectoral fins, though these are rounded at the tips where the albacore's taper to a point. The first dorsal fin is a deep yellow and the second, which is smaller than the first, is a light yellow, as is the anal fin. It has 7–9 dorsal finlets and 7–8 anal finlets, dark blue and silvery white in color respectively, matching the part of the fish's body they are on. The caudal fin is also silvery white. At 1.4 m (4 ft 7 in) maximum length, the albacore is the smallest of the bluefin tuna. It reaches sexual maturity at 0.9 m (2 ft 11 in) and its common length is only slightly larger at 1.0 m (3 ft 3 in). Males and females exhibit no sexual dimorphism.
The albacore has a cosmopolitan distribution in tropical and temperate waters across the globe and in every ocean as well as the Mediterranean Sea.
Its latitudinal range extends from 59°N to 46°S. Its temperature range is 10–25 °C (50–77 °F). Its depth range is 0–600 m (0–1,969 ft; 0–328 fathoms) in the epipelagic and mesopelagic zones. It is most often found in surface waters 15.6–19.4 °C (60.1–66.9 °F) in temperature, though larger individuals can be found in deeper waters 13.5–25.2 °C (56.3–77.4 °F). It can survive at temperatures as low as 9.5 °C (49.1 °F) for short periods of time. It favors areas where warm and cool water mix.
A highly migratory species, schools of albacore travel great distances, though Atlantic and Pacific populations do not appear to mix. North Pacific albacore migrate to two regions of the Northeast Pacific: one off the northern part of Baja California, Mexico, and the other off the coasts of Washington and Oregon. Every summer, North Atlantic albacore head to the Bay of Biscay off of France and Spain, but now arrive about 8 days earlier than they did 40 years ago.
Since the 1970s the NOAA Fisheries, Southwest Fisheries Science Center (SWFSC) has collaborated with American Fishermen's Research Foundation (AFRF) in tagging studies of albacore in the North Pacific. Through these studies we have learned that juvenile albacore (to 2 years of age) make trans-Pacific migrations in their younger years between Japan and the West coast of North America. To date over 24,000 albacore have been tagged with conventional dart tags and 1,245 of these have been recovered. In Spring of 2001 AFRF and the SWFSC began a pilot project to learn more about the migration habits of North Pacific albacore, Thunnus alalunga in an effort to allow the incorporation of detailed migration movements into stock assessment models. Archival tags are a recent technical innovation that are being used to collect daily locations (through light level data recorded by the tag), internal temperature of the fish's abdomen, ambient water temperature, and depth. Genetic research using ddRAD sequencing indicates that albacore migrate between the North and South Pacific oceans across the equator.
The albacore is a powerful, hard-hitting predator that forms mixed schools with skipjack tuna, yellowfin tuna, and bluefin tuna, sometimes around floating objects like sargassum weeds. Schools of albacore are highly migratory within bodies of water and segregated by maturity, with older fish tending to form more compact groups. Of those caught by humans, immature albacore have a 1:1 sex ratio while older albacore are mostly male. In the Atlantic Ocean, older fish are found in cooler waters. The opposite is true for the Pacific Ocean, where fish are found more abundantly along thermal discontinuities. Depth range also varies by location: Atlantic fish dive as deep as 600 m (2,000 ft) where Pacific fish reach only 380 m (1,250 ft) in depth. In the northeast Atlantic, feeding migrations to productive areas occur during the summer. Due to climate changes over the last 40 years, the timing and spatial distribution of the albacore have also changed.
Albacore show a broad range of behavioral differences by region. In Baja California, albacore make frequent dives to depths exceeding 200 m (660 ft) during the day and stay near the surface at night, while off the coast of Washington and Oregon they stay near the surface the entire day. Albacore never really rest; their need for oxygen means they must always be on the move.
The albacore's reproduction is oviparous and a 20 kg (44 lb) female can produce between 2–3 million eggs per spawning, which usually takes place between November and February. Eggs mature outside of the female's body and hatch in 1–2 days, after which fry begin to grow quickly. For the first year of their lives, juveniles remain close to the place where they were hatched. They begin to migrate after their first year. Albacore have a lifespan of 11–12 years, but they reach reproductive maturity at around 5–6 years.
A large majority of albacore have larger right testes or ovaries, depending on sex. Albacore have asynchronous oocyte development, that is their immature egg cells do not develop at regular intervals. The creation of ova, known as oogenesis, begins with the rapid production of oogonia (undifferentiated germ cells that give rise to oocytes) by mitotic separations in the oogonial nests of female tuna. The resulting oocytes are cast en masse into the sea, where full development and later fertilization take place.
Albacore tuna are pelagic predators - open-sea hunters. Their diets vary very little from season to season. Unlike other tuna that eat primarily fish, for example the bigeye and yellowfin tuna, the albacore's main source of food is cephalopods. The most abundant cephalopod in its diet is Heteroteuthis dispar, a tiny deep-water squid found in the Mediterranean Sea and Atlantic Ocean. Another cephalopod species preyed upon is Berryteuthis anonychus. Other food sources of the albacore include fish (including Cololabis saira, Engraulis japonicus, and Engraulis mordax), crustaceans, and gelatinous organisms. Not much is known about the food pattern of the albacore, however, mostly because it dives over 400 m (1,300 ft) underwater when searching for food, and tagging and tracking has been unsuccessful thus far.
