Albacore tuna  (Thunnus alalunga)

Classified as Data Deficient (DD) on the IUCN Red List 2007. The South Atlantic stock is classified as Critically Endangered (CR) and the North Atlantic stock is classified as Vulnerable (VU) (1).

This large, oceanic fish is built for speed, with a torpedo-shaped body, smooth skin and streamlined fins (3). The albacore tuna is characterized by a dark yellow first dorsal fin and a pale yellow second dorsal fin (4). The pectoral fins, found on each side of the body, are exceptionally long, and the crescent-shaped, deeply-forked tail fin helps generate the power required to maintain the albacore tuna’s impressive speeds. The albacore tuna is metallic dark blue on the back, with silvery-white sides and belly (3).

Occurs in tropical and temperate waters of all oceans, including the Mediterranean Sea, from 50°N to 40°S. The Atlantic and Pacific Oceans both hold at least two albacore tuna stocks (northern and southern), each with distinct spawning areas and rarely crossing the warm equatorial waters (2).

An epipelagic and mesopelagic, oceanic species, found in waters of 13.5° to 25.2°C. The albacore tuna may tolerate temperatures as low as 9.5°C for short periods (2).

The albacore tuna forms schools, which can be up to an astonishing 30 kilometres wide (3). These enormous schools are sometimes associated with floating objects, such as sargassum weeds, and they may also form mixed schools with other tuna species, such as skipjack, yellowfin and bluefin tuna (2). In these schools, the albacore tuna undertakes great migrations in search of the best feeding and spawning grounds, strongly influenced by large oceanic phenomena such as El Niño (5) (6). Albacore tuna are able to reach impressive speeds, of up to 80 kilometres per hour, due to their highly evolved circulatory system that reduces the loss of heat generated by increased muscular activity. This allows them to maintain their body temperature at a higher level than the surrounding water, keeping their muscles warm and working efficiently (3). Unlike many fish, albacore tuna are not able to pump water over their gills to obtain oxygen from the surrounding water, and therefore need to swim constantly with their mouth open, to force water over their gills. A high volume and pressure of blood, and great haemoglobin concentration, all increases the ability of the fish to absorb the essential oxygen (3).

Albacore tuna are believed to be pelagic spawners, meaning that the female releases her eggs, and the male his sperm, into open water, often near the water’s surface (3). A female albacore tuna is capable of producing two to three million eggs per spawning season, which are released in at least two batches (2); however, the majority of these eggs will not survive to be adults (3). The tiny eggs are just one millimetre in diameter and are enclosed in an oil droplet to enable them to remain buoyant in the ocean. The eggs are fertilized by the male, and the resulting fertilized eggs develop rapidly, with hatching occurring in less than 48 hours (3).

The large albacore tuna is one of the top carnivores within the ocean regions it inhabits, and it preys voraciously upon smaller schooling fish such as sardines and anchovy, and squid, consuming around 25 percent of its weight every day. The albacore tuna itself becomes prey for larger species of tuna, billfish and sharks (3).

For many years, important fisheries have existed for the albacore tuna in the Atlantic and Pacific Oceans. As efforts to catch fish have increased, the world catch of albacore tuna has been gradually declining and many stocks are now over-fished, or fully exploited and nearing a situation of over-fishing (2) (5). The North Atlantic stock has declined to about one quarter of the peak levels estimated for the 1940s, and likewise, the South Atlantic stock has been reduced by fisheries to about 25 percent of its un-fished level (7). While there are regulations regarding the amount of albacore tuna that can be caught in many areas, enforcing such fishing laws can be challenging as the boats operate on the high seas far from observation (8).

In the Atlantic Ocean, the International Commission for the Conservation of Atlantic Tunas (ICCAT) is responsible for the conservation of the albacore tuna. Based on scientific evidence, the Commission can adopt recommendations and resolutions aimed at maintaining populations of tuna species at levels which will permit maximum sustainable catch (7). An assessment of albacore tuna stocks undertaken in 2007 led to the recommendation that the total allowable catch should be reduced for the North Atlantic stock if it is to recover from its over-fished condition. Even though the South Atlantic stock was also found to be over-fished, the Commission considered that the current management regulations for the South Atlantic stock are sufficient for its recovery (7). Similarly, the Inter-American Tropical Tuna Commission (IATTC) is responsible for the conservation and management of fisheries for tunas in the eastern Pacific Ocean (9). While in these areas, stocks of the albacore tuna are studied, monitored and fisheries regulated, elsewhere the status of this species is not so clear, hence the World Conservation Union (IUCN) has assessed it as Data Deficient (1). Hopefully further knowledge will soon come to light, to ensure that throughout its range, this important tuna species will be exploited sustainably without threat to its continued survival.

For more information on the albacore tuna see:

Southwest Fisheries Science Center - Albacore Research:
swfsc.noaa.gov/textblock.aspx?Division=FRD&id=1168&ParentMenuId=139

For up-to-date information on the status of albacore tuna stocks in the Atlantic see:

ICCAT:
www.iccat.es

• Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
• El Niño: a natural phenomenon that happens every 4 to 12 years, and lasts for several months, when upwelling of cold, nutrient-rich water does not occur. This causes the warming of ocean surface water off the western coast of South America and causes die-offs of plankton and fish. It also affects Pacific jet stream winds, altering storm tracks and creating unusual weather patterns in various parts of the world.
• Epipelagic: inhabiting the sunlit region of the ocean between the surface and a depth of 200 metres.
• Haemoglobin: a protein found in red blood cells that is responsible for carrying oxygen around the body.
• Mesopelagic: inhabiting the region of the ocean extending from 200 metres down to around 1,000 metres below sea level.
• Pectoral fins: in fish, the pair of fins that are found one on each side of the body just behind the gills. They are generally used for balancing and braking.
• Spawning: the production or depositing of large quantities of eggs in water.

1. IUCN Red List (October, 2007)
   http://www.iucnredlist.org/
2. Collette, B.B. and Nauen, C.E. (1983) FAO Species Catalogue. Vol. 2: Scombrids of the World. An annotated and illustrated catalogue of tunas, mackerels, bonitos and related species known to date.Food and Agriculture Organization of the United Nations, Rome.
3. Southwest Fisheries Science Center: Albacore Research (January, 2008)
   http://swfsc.noaa.gov/textblock.aspx?Division=FRD&id=1168&ParentMenuId=139
4. NSW Department of Primary Industries (January, 2008)
   http://www.dpi.nsw.gov.au/fisheries/recreational/saltwater-fishing/sw-species/albacore
5. Atuna: Tuna Species Guide (January, 2008)
   http://www.atuna.com/
6. Kimura, S., Nakai, M. and Sugimoto, T. (1997) Migration of alabcore, Thunnus alalunga, in the North Pacific Ocean in relation to large oceanic phenomena. Fisheries Oceanography, 6 (2): 51 - 57.
7. ICCAT (January, 2008)
   http://www.iccat.es/
8. SeaChoice (January, 2008)
   http://www.seachoice.org/profile/70/view
9. IATTC (January, 2008)
   http://www.iattc.org/