Albacore

From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Albacore (disambiguation).
Albacore
Thunnus alalunga.png
Conservation status
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Scombridae
Subfamily: Scombrinae
Tribe: Thunnini
Genus: Thunnus
Subgenus: Thunnus
Species: T. alalunga
Binomial name
Thunnus alalunga
(Bonnaterre, 1788)
Synonyms[2]
  • Thunnus germo (Lacepède, 1801)
  • Scomber alalunga Bonnaterre, 1788

The albacore, Thunnus alalunga, is a species of tuna in the family Scombridae. This species is also called albacore fish, albacore tuna, albicore, albie, pigfish, tombo ahi, binnaga, Pacific albacore, German bonito (but see bonito), longfin, longfin tuna, longfin tunny, or even just tuna. It is the only tuna species which may be marketed as "white meat tuna" in the United States. It is found in the open waters of all tropical and temperate oceans, and the Mediterranean Sea.

Albacore is a prized food, and the albacore fishery is economically significant. Methods of fishing include pole and line, long-line fishing, trolling, and some purse seining. It is also sought after by sport fishers.

Lifecycle[edit]

During spawning, females produce between 800,000 and 2.6 million eggs which hatch in about one or two days. After the eggs hatch, the fish begin to grow quickly and they remain close to the place where they were hatched for the first year of their lives. They begin to migrate after their first year. Albacore tuna have a lifespan of 11 to 12 years, but they reach reproductive maturity at around five to six years.[3]

Reproductive process[edit]

Despite having no sexual dimorphism, tuna are dioecious (males and females have different sexual organs). Oddly, a large majority of tuna have heavier and larger right testes and ovaries in males and females, respectively. Their eggs, which mature and hatch outside of the female's body, are typically restricted from November to February for spawning.[4] Albacore have asynchronous oocyte development. An oocyte, which is an immature egg cell, does not develop at regular intervals in albacore. The creation of ova, known as ooegenesis, 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.[5]

Genetic variation from other tuna species[edit]

Not only do albacore differ genetically from other tuna species, but they also differ to some degree among themselves. The variation in six specific nucleotide sites (organic molecules that form the basic building blocks of nucleic acids) differentiate each species of tuna. In the nucleotide positions 35, 62, 68, 89, 227, and 260, albacore have guanine, thymine, cytosine/guanine, guanine, adenine, and thymine, respectively. They differ from blackfin tuna which have thymine, guanine, and cytosine at the corresponding 68, 89, 227, and 260 positions. Similarly, albacore are different from yellowfin tuna in all but two of the six nucleotide positions, 35 and 260, and hold even less genetic commonality with the bigeye tuna, which is only identical in the 260 position. The intervariance that occurs between albacore is a result of this 68 nucleotide position that can be either cytosine or guanine. No visible external difference can be noted between albacore, which have cytosine at the 68 position, and those that have guanine at the same nucleotide site.[6]

Diet[edit]

Albacore tuna are pelagic predators - open-sea hunters. Their diets vary very little during the different seasons. Distinct from its two counterparts bigeye and yellowfin tuna that primarily eat fish, albacore tuna's main source of food is cephalopods, which are also eaten by the other two species of tuna, albeit in smaller proportions. The most abundant cephalopods in its diet are Heteroteuthis dispar (a tiny deep-water squid found in the Mediterranean Sea and Atlantic Ocean). Other food sources of the albacore include fish, crustaceans, and gelatinous organisms. Not much is known about the food pattern of albacore tuna, however, mostly because they dive over 400 m underwater when searching for food, and tagging and tracking them has been unsuccessful thus far.[7][8]

Migration and behavior[edit]

The North Pacific albacore migrate to two regions of the Northeast Pacific; one is off the northern part of Baja California, Mexico, and the other is off the coast of Washington and Oregon. Albacore tuna show a broad range of behavioral differences. In Baja California, the tuna 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 the tuna stay near the surface the entire day.[9] The albacore never really rest; they must always be on the move because of their demand for oxygen. Due to so much energy being used by the constant movement, a typical tuna may eat one-quarter its own weight in food in one day.[10] The northeast albacore tuna performs feeding migrations to productive areas of the Northeast Atlantic during the summer. Due to climate change over the last 40 years, the timing and spatial distribution of the albacore tuna has also changed. Every summer, the North Atlantic albacore tuna head to the Bay of Biscay, but now arrive about 8 days earlier than they did 40 years ago.[11][12]

Anatomy and physical description[edit]

The albacore tuna's pectoral fin is extremely long and extends well beyond the front of the anal fin except in tuna under 30 cm long. Its average size is about 1.4 m and can weigh up to 60 kg. The albacore's fins consist of seven to 9 dorsal finlets, seven or eight anal finlets, and 25-31 gill rakers. This tuna is dark blue dorsally, and shades of silvery white ventrally. The first dorsal fin is a deep yellow. The second dorsal fin and the anal fin are a light yellow. The caudal fin is white-edged, while the anal finlets are dark.[13]

Other species called albacore[edit]

In some parts of the world, other species may be called "albacore":

Consumers, albacore, and sustainable fisheries[edit]

A number of programs have been developed to help consumers identify and support responsible and sustainable fisheries. Perhaps the most widely accepted of these programs is that of the Marine Stewardship Council (MSC). Several albacore fisheries have been certified as sustainable according to MSC standards, including the U.S. North and South Pacific albacore pole and line and troll/jig fisheries ("pole and troll"), Canadian North Pacific troll fishery, and the New Zealand South Pacific troll fishery.[14]

The United States government's "Fishwatch" program seeks to provide consumers with accurate and timely information on U.S. seafood fisheries.[15]

Root of endangerment[edit]

The hunting and killing of albacore tuna for commercial use began at the beginning of the 20th century. The migratory patterns of the fish brought droves of albacore schools near the coastline of Southern California, which sparked the start of commercial albacore fishing. In 1903, 700 cases of albacore were used as an experimental pack which ultimately lead to the development of the U.S. tuna-canning industry. The experiment was a huge success, and the commercial fishery expanded rapidly due to the high level of demand for canned tuna, which became higher than the supply of tuna, causing a significant loss in the albacore tuna population. By the 1920s, the industry expanded further and three other species of tuna, bluefin, yellowfin, and skipjack, were also being canned. However, the canning of other tuna species did not help the recovery of albacore tuna populations because it is the only tuna species that can be marketed as "white meat tuna". Fisheries use this label as a way to charge a premium price at the dock and in the can. Over the years, demand for canned tuna continued to rise, causing fisheries to resort to using "ranching" methods. Ranching is the process of catching young tuna from the wild and keeping them alive in captivity with artificial feeding. Albacore tuna are kept in captivity until they become full grown, at which time they are killed and their meat is used for canned tuna.[16]

Conservation efforts[edit]

Population numbers of albacore tuna are plummeting fast due to growing human populations and rising food demands.[17] However, conservationists have been making strides to help strengthen the species. Scientists have begun breaking ground on better forms of long-term protection of tuna such by including electronic tag data, genetics and microchemistry in their efforts. The re-creation of the electronic tag is expected to play a huge part in the conservation of albacore tuna as it is far more advanced than previous electronic tag devices. In the new tags, trackers record fish depth and sea temperature every few minutes.[18]

Mercury levels[edit]

See also: Mercury in fish

Like other fish, albacore accumulates methylmercury in body tissue over time. Methylmercury is removed from the body naturally, but it may take over a year for the levels to drop significantly. Thus, it may remain in a woman from before she becomes pregnant. Ranging from as low as .027 ppm (parts per million) to .26 ppm, the average total mercury content of albacore is .14 ± .05 ppm. Larger fish tend to bioaccumulate higher methylmercury levels. For the most part, there is positive correlation between an albacore's methylmercury measurement and its weight and length.[19]

Recent studies from the U.S. and Canada show that the albacore caught by the American albacore fishing fleet off the coasts of Washington, Oregon, and California have far lower mercury levels than in previous years.[20] Albacore caught in this region also show methylmercury levels well below the 1.0 ppm mercury standard set by The U.S. Food and Drug Administration(FDA).[19] Nevertheless, since mercury does take time to be removed from the body, albacore tuna should be eaten in moderation.

Harmful effects of mercury on humans[edit]

Main article: Mercury poisoning

With both high and low levels of exposure to it, mercury can be extremely harmful to people. Infants with higher prenatal exposure to mercury than the FDA suggested level have delayed psychomotor development (the relationship between cognitive functions and physical movement) in the first year of life. Higher exposure to mercury (not prenatal) can have even more dire consequences. These include, but are not limited to: loss of neurons in the brain lobes, blindness, deafness, and mental retardation.[21]

Supply[edit]

Management and stock assessment are applied to separate stocks of albacore believed to occur in the North Pacific, South Pacific, Indian Ocean, North Atlantic and South Atlantic.

SeaChoice ranks albacore as a "best choice" for consumers, although notes some "moderate concerns" regarding the management effectiveness (in particular, no definitive assessment of the albacore stock of the Indian Ocean fishery has taken place), and "moderate concern" over the fishing stock, especially regarding the North Atlantic albacore population, which the National Marine Fisheries Service (NMFS) considers overfished with overfishing still occurring. The southern Atlantic stock is also considered (in 2007) overfished but not currently experiencing overfishing. The North Pacific and South Pacific albacore stocks are not overfished and are not experiencing overfishing.[22]

Fisheries of Pacific islands and territories[edit]

Many Pacific island countries and territories (PICTs) heavily rely on oceanic fisheries for economic development and food security. The albacore tuna is one of the main four species of tuna that support oceanic fisheries along with the skipjack, yellowfin, and the bigeye tunas. Domestic tuna fleets and local fish processing operations contribute from 3-20% of the gross domestic product in four PICTs. License fees from foreign ships provide an average of 3-40% of government revenue for seven different PICTs. Processing facilities and tuna fishing vessels provide more than 12,000 jobs for workers in the Pacific islands. Fish provide 50-90% of dietary animal protein in rural areas of PICTs.[23]

Gallery[edit]

References[edit]

  1. ^ Collette B and 34 others (2011). "Thunnus alalunga". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 13 January 2012. 
  2. ^ "Thunnus alalunga". Integrated Taxonomic Information System. Retrieved 9 December 2012. 
  3. ^ "Albacore Tuna." This fish. ThisFish & Ecotrust Canada . Web. 25 Oct 2013. <http://thisfish.info/fishery/species/albacore-tuna/>.
  4. ^ Ramon, D. (4 October 1996). "Spawning seasonality of albacore, Thunnus alalunga, in the South Pacific Ocean". Fishery Bulletin 94 (4): 724–733. 
  5. ^ Schaefer, Kurt (2001). [(http://www.sciencedirect.com/science/article/pii/S1546509801190072) "Reproductive biology of tunas"]. Fish Physiology 19: 225–270. doi:10.1016/s1546-5098(01)19007-2. Retrieved 21 October 2013. 
  6. ^ Barlett, Silvia, E.; Davidson S., William (1991). "Identification of Thunnus Tuna Species by the Polymerase Chain Reaction and Direct Sequence Analysis of their Mitochondria Cytochrome b Genes". Canadian Journal of Fisheries 48: 309–418. doi:10.1139/f91-043. 
  7. ^ Bertrand, A.; Bard, F.; Josse, E. (1 May 2002). "Tuna food habits related to the micronekton distribution in French Polynesia". Marine Biology 140 (5): 1023–1037. doi:10.1007/s00227-001-0776-3. 
  8. ^ Consoli, P.; Romeo, T., Battaglia, P., Castriota, L., Esposito, V., Andaloro, F. (1 July 2008). "Feeding habits of the albacore tuna Thunnus alalunga (Perciformes, Scombridae) from central Mediterranean Sea". Marine Biology 155 (1): 113–120. doi:10.1007/s00227-008-1012-1. Retrieved 21 October 2013. 
  9. ^ Childers, John; Stephanie Snyder; Suzanne Kohin (1 January 2011). "Migration and behavior of juvenile North Pacific albacore (Thunnus alalunga)". FISHERIES OCEANOGRAPHY 2 (3): 157–173. Retrieved 25 October 2013. 
  10. ^ "All About A Tuna’s Life." Tuna Facts & Life Cycle. Bumble Bee Foods, LLC. Web. 25 Oct 2013. <http://www.bumblebee.com/about/seafood-school/life/>.
  11. ^ Dufour, Florence; Haritz Arrizabalaga; Josu Santiago (July 2010). "Climate impacts on albacore and bluefin tunas migrations phenology and spatial distribution.". Progress in Oceanography 86 (1/2): 283–290. doi:10.1016/j.pocean.2010.04.007. 
  12. ^ http://ehis.ebscohost.com/ehost/detail?vid=4&sid=a8b9f830-3b2d-41ff-99a8-bb41b1559822%40sessionmgr15&hid=17&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aph&AN=51810422.  Missing or empty |title= (help)
  13. ^ http://wdfw.wa.gov/fishing/tuna/.  Missing or empty |title= (help)
  14. ^ Marine Stewardship Council. "List of all certified fisheries". MSC.org. Retrieved 15 February 2012. 
  15. ^ NOAA Fishwatch - Pacific albacore
  16. ^ von Borks, Manfred (June 2011). "Pacific Juvenile Albacore in the Ensenada/San Diego Area History, Biology, Lures, Tactics and Night Fishing". Rev 6 Final Edition. 
  17. ^ Burgess, Matthew; Stephen Polasky; David Tilman (16 September 2013). "Predicting overfishing and extinction threats in multispecies fisheries". Proceedings for the National Academy of Sciences of the United States of America 110: 15947. doi:10.1073/pnas.1314472110. 
  18. ^ Arnold, Geoff (18 September 2008). "Time to can the tuna fisheries?". Nature 455 (7211): 286–287. doi:10.1038/455286a. 
  19. ^ a b Morrissey, T., Michael; Rasmussen, Rosalee; Okada, Tomoko (11 October 2008). "Mercury Content in Pacific Troll-Caught Albacore Tuna (Thunnus alalunga)". Journal of Aquatic Food Product Technology 13 (4): 41–52. doi:10.1300/J030v13n04_04. Retrieved 24 October 2013. 
  20. ^ http://www.nmfs.noaa.gov/fishwatch/docs/OSU_Mercury_Study.pdf
  21. ^ Jedrychowski, Wieslaw; et al. (June 2006). "Effects of Prenatal Exposure to Mercury on Cognitive and Psychomotor Function in One-Year-Old Infants: Epidemiologic Cohort Study in Poland". Annals of Epidemiology 16 (6): 439–447. doi:10.1016/j.annepidem.2005.06.059. Retrieved 24 October 2013. 
  22. ^ "Tuna: Albacore". SeaChoice. Retrieved 2007-02-21. 
  23. ^ Bell, J. D.; Reid, C.; Batty, M. J.; Lehodey, P.; Rodwell, L.; Hobday, A. J.; Johnson, J. E.; Demmke, A. (2012). "Effects of climate change on oceanic fisheries in the tropical Pacific: Implications for economic development and food security". Climatic Change 119: 199. doi:10.1007/s10584-012-0606-2.  edit

Other references[edit]

External links[edit]