Kamis, 26 Maret 2015

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


Albacore

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.

Reproductive process

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. 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.

Genetic variation from other tuna species


Albacore

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) in a single mitochondrial gene 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.

Diet


Albacore

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.

Migration and behavior


Albacore

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. 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. 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.

Anatomy and physical description


Albacore

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.

Other species called albacore



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

  • Blackfin tuna Thunnus atlanticus (albacore)
  • Yellowfin tuna Thunnus albacares (albacore, autumn albacore, yellowfinned albacore)
  • Yellowtail amberjack Seriola lalandi (albacore)
  • Kawakawa Euthynnus affinis (false albacore)
  • Little tunny Euthynnus alletteratus (false albacore)

Consumers, albacore, and sustainable fisheries


Albacore

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.

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

Harvest History



The harvest 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, by the 1920s, the industry expanded further and three other species of tuna, bluefin, yellowfin, and skipjack, were also being canned. However, Albacore tuna is the only species that can be marketed as "white meat tuna". The canning industry uses this label as a way to differentiate canned albacore from other types of tuna.

Conservation efforts


Albacore

Albacore are managed by four tuna Regional Fisheries Management Organizations, (RFMO's) include the Western and Central Pacific Fisheries Commission (WCPFC), the Inter-American Tropical Tuna Commission (IATTC), the International Commission for the Conservation of Atlantic Tunas (ICCAT), and the Indian Ocean Tuna Commission (IOTC). ICCAT has established catch quotas in the North and South Atlantic.There is substantial uncertainty on current stock status, since different models and assumptions provide a wide range of estimates However, most of them agreed on the view that spawning stock biomass decreased since the 1930s and started to recover since the mid-1990s Most of the model formulations, as well as the base case,concluded that currently the stock is not undergoing overfishing but the spawning stock biomass is overfished. IOTC judges albacore in the Indian Ocean are not overfished, but maintaining or increasing effort in the core albacore fishing grounds is likely to result in further declines in albacore biomass. The WCPFC has accessed the South Pacific Albacore are not over fished. In the 2014 assessment,the International Scientific Committee for Tuna and Tuna-like Species in North Pacific Ocean (ISC), Albacore Working Group (ALBWG), found estimates of total stock biomass(age-1 and older)show a long term decline from the early 1970s to 1990 followed by a recovery through the 1990s and subsequent fluctuations without trend in the 2000s. The ALBWG concludes that the stock is likely not in an overfished condition at present. All of the tuna Regional Fisheries Management Organizations noted that there is uncertainty surrounding the life history and biology of Tunas and tuna like species including age and growth, maturity, and natural mortality rates; uncertainty about the quality and completeness of available data; and uncertainty about recruitment.

In the North Pacific, NOAA Fisheries, Southwest Fisheries Science Center (SWFSC). Since the 1970s the SWFSC has collaborated with American Fishermen's Research Foundation (AFRF) in tagging studies of albacore. Through these studies we have learned that juvenile albacore (2 to 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.

Mercury levels



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.

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. 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). 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

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.

Supply



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.

Fisheries of Pacific islands and territories



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.

Gallery



References



Other references



  • North Atlantic albacore tuna NOAA FishWatch. Retrieved 5 November 2012.
  • Pacific albacore tuna NOAA FishWatch. Retrieved 5 November 2012.

External links



  • Marine Stewardship Council (international independent certification of sustainable fisheries)
  • American Albacore Fishing Association (MSC certified Pacific U.S. "pole & troll" albacore)
  • Wild Pacific Albacore
  • NOAA Fishwatch
  • American Fishermens Research Foundation
  • Western Fishboat Owners Association
  • albatuna.com
  • TIME MAGAZINE: The Danger of Not Eating Tuna
  • Etymology of "albacore"
  • FishBase info for albacore
  • Communicating FDA advice on consumption of albacore tuna.
  • Albacore by R. Michael Laurs and Ronald C. Dotson, 1992, retrieved January 19, 2006.


 
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