Tuna species that are of commercial interest
It does not mean that the tuna species of noncommercial are not eaten. They are however not processed for consumption and are consumed by the local population.
The tuna species of commercial interest will be introduced hereafter (Name, Latin name and estimated catch in 2018) and in the text you find a hyperlink for more info on this specie.
Albacore is also known as longfin tuna. They are found in tropical and subtropical waters. It is a fierce hunter and their prey is more squid-oriented compared to other species in the tuna family.
Juvelines tend to stay in the area where they hatch for about one year. Subsequently (based on life cycle) they start migrating in schools of their own or with a school of Skipjack.
Albacore can grow to about 120 cm in length weighing up to around 40 kg. Like Bluefin and Bigeye Tuna, Albacore prefer to live at a depth of 250-300 meters.
The majority of the Albacore tuna goes to the canning industry and is a popular product in the USA.
Bonito del Norte
AGE, SIZE & WEIGHT
Albacore is bigger than Skipjack ,but smaller than the other commercial tuna species. A mature female measures about 85-90 cm and weighs about 20 kg. A mature male measures about 90 cm and weighs 24-25 kg. The full grown mature female is slightly smaller (110 cm) compared to the full grown male (128 cm). Albacore live around 11-12 years. This does not differ much between the different oceans.
In the Atlantic, Indian and the Pacific Ocean, in tropical and subtropical waters, between 60 ° North and 47° South. They ‘re present in the Mediterranean Sea, but not in significant numbers.
Juvenile albacore tuna swim in schools mixed with other juvenile tuna (skipjack, yellowfin as well as bluefin tuna). Once they’re mature, they tend to form their own schools. The older the albacore tuna grow, the more compact the schools become.
Younger albacore tuna remains closer to the surface. The older tuna prefer a depth of 250-300 meters. Their behaviour is different in various regions. In the Atlantic Ocean, the older albacore tuna tends to move and stay in colder water, while the opposite is true in the Pacific Ocean.
In the Atlantic Ocean, albacore tuna dives under 600 meter, while in the Pacific Ocean 380 meters tends to be the limit.
Albacore tuna migrate at constant high speed (up to 80 km/h) over long distances in all oceans. There is a seasonal pattern to the migration.
Albacore tuna has a different diet compared to the other tuna. The main part of the diet is cephalopods, but besides this they also eat small fish, crustaceans and gelatinous organisms. Often they dive more than 400 meters to obtain food, but there is not much known about what exactly they eat at that depth.
This specie is quite late mature compared to the other tuna species. The first spawn when they are 5-6 years old, but more often they reach maturity at 10-11 years of age. The female can release 0,9-2,6m eggs per spawning. The eggs remain on or close to the surface where hatching occurs within 48 hours. Other fish feed on the eggs and many are lost. The peak period for spawning is March – April but it can go through up to September.
Adult albacore tuna is difficult to catch. Fisherman often use longliners, but hardly any other fishing gear. As mentioned, young albacore tuna remains on or close to the surface, so easier to catch with Pole & Line or purse seine.
In the United States of America is a substantial market for tinned albacore tuna. In Spain, it is well known as the Bonito del Norte. The price per can is higher compared to skipjack and yellowfin tuna. The texture (solid) and taste of albacore tuna is completely different from all other tinned tuna with exception of Bluefin. Catches are limited, so there is no expectation that the consumption will increase.
There are three bluefin tuna species:
- Atlantic bluefin tuna (Thunnus Thynus)
- Pacific bluefin tuna (Thunnus)
- Southern bluefin tuna (Thunnus Maccoyii)
Bluefin tuna is a fascinating fish, which can grow up to 2,6 meters when mature. It’s highly complex anatomy allows them to swim in much colder water enabling them to hunt for their prey in very deep water (up to 2.500 meters).
Bluefin Tuna is the most famous and also the most expensive tuna on the market. This fame resulted from the high price fetched for a single Bluefin Tuna at the most popular fish market in Tokyo-Japan. This was reported in the news a few years ago at the beginning of the year when the bluefin tuna stock in the Mediterranean was in bad shape.
The management of the bluefin tuna stocks in the Atlantic and the Pacific Ocean is on an acceptable level. Applying stricter regulations in the Pacific Ocean is more complicated than in the Atlantic (and Mediteranian) oceans.
It is good to note that the annual worldwide catch of BLUEFIN TUNA is only 50.000 ton. Years ago, many people mistook the bad news about the Bluefin tuna stock in the Mediterranean Sea as a sign that ALL tuna stocks were in danger. Fortunately, this news only related to the Bluefin tuna stock. Furthermore, thanks to drastic measures, Bluefin stocks have recovered in recent years.
The Bluefin Tuna catch period is always short (a few days). The catch consists mainly of smaller fish, which transfers from the net to caches. The tuna farmers feed the tuna with fatty fish to get nice soft flesh and delicious taste.
Since bigger Bluefin Tuna can swim in colder waters this specie can sometimes be found in the waters of Iceland and Norway.
Southern Bluefin Tuna migrate year round:
- In the waters of Australia they’re building up their reserves in winter time
- Thereafter moving to the tropical waters of the northwest Indian Ocean for spawning from spring to autumn to return to Australia thereafter.
A return leg of 10.000km is justified by science as part of the hunting process. Scientists have discovered that some of the tagged Southern Bluefin Tuna covered distances of up to 114.000 km in 4,2 years.
Juveniles tend to follow this pattern for 1-4 years and once matured they leave the shallow waters and go mostly on their own into the Indian Ocean.
They prefer seawater of 18-20°C, but some stay in water of 10°C or even less for up to 10 hours. Nevertheless they only spawn in water with a minimum temperature of 24°C. During the day they stay at a depth between 150–600m, but at night they remain closer to the surface at a depth of 50m or less.
They are usually located between 30-50° Southern Latitude, but mostly in the Western & Central part of the Pacific Ocean
They are considered mature around 1,5 meters and not younger than 8 years
Spawning pattern South-East of Java – Indonesia
On average they grow 1,5 cm per month
Annual quota is 17.647 ton (2018-2020) with the major quota holders being Australia and Japan
Max. size & weight 250 cm and 260 kg.
Max. age 40 years
The texture of their meat is highly appreciated by many fish lovers, mainly in Asia. The demand has led to overfishing, which nearly destroyed the stock. In 2006, heavy underreporting of catches was observed. Due to substantial reduction of the quota
In 2006 and 2009, the stock is recovering.
This specie is generally smaller than the BLUE FIN tuna (and less valuable), but still a good 160 cm once 7 years old. Unsurprisingly it has big eyes for being able to see in low light. Out of all the tuna species, it is the only which dives deep after sunrise (below 200m) and appears again at 50m or less after dusk. BIGEYE TUNA are mature around 3,5 years.
The young Bigeye tuna (juveniles) tend to swim with other small tuna, like Skipjack or Yellowfin Tuna. These schools can associate themselves with floating objects, natural or man-made FAD’s or whales. Tuna purse seiners like to set their net on such a school, but the fish is relatively small.
It has a significant impact on replenishing the stock since you remove a lot of potential reproducers from the sea. If mankind would limit the use of FAD’s, it will have a smaller impact on the tuna stocks.
In order to be served in a restaurant the Bigeye Tuna has to be caught with lines with hooks and directly frozen below -60 ° C. Bigeye Tuna caught any other way mostly end up being tinned, due to its diminished quality. However, these days canneries prefer to dump it on the local market instead of going through the tinning process.
Ahi (also used for Yellowfin Tuna)
AGE, SIZE & WEIGHT
Bigeye Tuna grows fast and are mature around the age of 3,5 years with already a minimum length of 100-115cm.
They can live up to 16 years ( 9 years estimated for the Atlantic Ocean) old and reach a maximum length and weight of 200 cm and 210 kg. However 180 cm and 180 kg is the more common size and weight.
Atlantic Ocean between 50° North and 40° South
Indian Ocean West, off Somalia
East, India but in the last few years not so much
Pacific Ocean wide spread
It is a powerful fish and slightly smaller than Bluefin. The anatomy allows it to stay in colder waters with lower oxygen levels. It seems that the body needs to remain warm during the night.
The Bigeye’s big eyes assist in hunting for prey in deeper waters (250-500m) – below the thermocline – where visibility is limited, which is what they do during the day. After dusk they move up and to warmer shallower water (50-100m depth) to warm their muscles.
Young Bigeye tuna swim in schools mixed with other small tuna and fish. The schools often associate with whales, FAD’s or natural objects. Once they get older they tend to break away and move on their own.
Their diet is mainly epipelagic (on the surface) and mesopelagic (between 200-600 meters) fish, crustaceans and cephalopods.
Bigeye tuna is mature between 2-4 years old. They do not spawn all year round, but spawning takes place in the
- Gulf of Guinea (December to April)
- Brazil/Golf of Guinea, whole year in water > 24°C
- Cape Verde/Senegal, July-September
- Congo/Angola, November to February
- Indian Ocean, Eastern part December-January but also in June
- Pacific Ocean, wide spread, but more in Eastern Pacific Ocean (70%)
Longliners target bigeye tuna and freeze them ultra (-60° C) for the sashimi and sushi market. Other gear, like tuna purse seiners and pole and line vessels, catch it mixed with other fish as by-catch. This by-catch is often sold in the local market or at the port of discharge.
Bigeye Tuna is not suitable for the canning market as in most consumer markets, taste and texture are not appreciated. However, as mentioned above, if you catch it with the right gear and treat the fish well, it is commercially very attractive.
Length abt. 105 cm @ 3 years
abt. 145 cm @ 5 years
abt. 163 cm @ 7 years
Max. size & weight abt. 200 cm and 210 kg.
Max. age 11 years recorded, but 15 years is possible
Yellowfin is found in the Atlantic, Indian and the Pacific oceans and for the most part in shallower waters. They always swim in schools to which they’re very loyal. They feed close to or at the surface on fish, crustacean and mollusc. In case they cannot find food, they go deeper or even form diving teams to go very deep for bringing prey to the surface. A Yellowfin Tuna is a savage eater sometimes swallows its prey whole.
Make no mistake, with its shape and muscles the Yellowfin tuna can reach a speed over 60+ km/hr. On top of this, they can maintain this speed for quite a while if they need to escape.
The biggest Yellowfin tuna caught was 220 cm and 193 kg. Putting the extremes aside, more common is in free school 40-120 kg for a good Yellowfin tuna.
The female can produce 10 million eggs per season, but many eggs will not survive. They serve as food for other life in the sea. As for all fish, their survival rate goes up significantly as they increase in size.
You can consume Yellowfin in cans or steaks or when fresh also sashimi-style. The steak is becoming more popular as a replacement for steaks of Swordfish, which are much more expensive.
Hawaiian AHI, this name is also used for Bigeye Tuna, Japan – Kihada Maguro, France – Albacore, Spain – Rabil
AGE, SIZE & WEIGHT
Juvenile Yellowfin tuna grow fast, weighing 3,5 kg after 18 months. The maturity stage is when the fish is approaching 120 cm in length and once 4 years they weigh in at 60+ kg.
The biggest angled Yellowfin tuna was 175 kg. (1977), but in free schools fishermen often find fish in the seize of 40-80/90 kg. or even more.
The life cycle of Yellowfin tuna is 4-7 years , which means that their period for reproduction is much shorter than for example that of Skipjack.
In the Atlantic, Indian and Pacific Ocean, in tropical and subtropical waters. In general, Yellowfin is not found in waters with a depth under 50 meters.
In the vertical column, Yellowfin is most comfortable between the surface and 100 m dept. There is evidence that they sometimes go real far under the thermocline, in search for food, but it is not part of their regular pattern.
Juvenile Yellowfin tuna swim in schools mixed with other juveniles tuna (Skipjack and Bigeye Tuna) as well as other small fish. Once they’re mature they go in schools their own way. They’re very social, swimming and hunting in schools and when necessary collectively defend their school when they’re under attack.
Juveniles feed themselves with planktonic crustaceans, small surface-dwelling fish. When they grow up, they change their diet to squid, scombrid fishes, juvenile Skipjack and deeper-dwelling fish.
The mature age of Yellowfin tuna is between 2 to 3,5 years and the length is between 90-120 cm.
They spawn all year-round with a peak in the summertime. Once they spawn they to do it roughly once a day. In one season they produce abt. 2 million eggs.
All gears can be used to catch Yellowfin Tuna. For Pole and Line vessels it is obligatory to use a FAD or natural log, as tuna migrate unless they stay under a FAD.
Tuna purse seiners can and do chase the bigger and more valuable Yellowfin. An extra advantage of this method is that there is hardly any by-catch. Unfortunately catch reports in all three oceans show that purse seiners perform fewer sets on free school and more on FAD’s.
Another selective method, besides Purse Seine Free School, is handline. This method is for catching bigger Yellowfin tuna. It can be performed with a small boat but also with a pole and line vessel. For the latter, it is a matter of changing gear.
Depending on the distance to the port, for handline you need conservation on board – either ice boxes, RSW tanks or a refrigerated hold. The majority of this catch goes for export in fresh condition, at a much higher price. Quality must be preserved at all times, because the trip can last 10-15 days.
Gillnet is another fishing gear to catch Yellowfin tuna. With this method is hardly selectivity but is practised in many coastal states.
Trolling is used in coastal waters for catching swordfish and marlin. Yellowfin tuna can swim in the same area and are often caught as well.
Most of the Yellowfin tuna ends up in cans, especially in the southern European countries. Besides this, you can buy frozen steaks in the supermarket or (parts of) fresh loins or steaks in foodservice markets.
Skipjack is the most abundant tuna species, which is not part of Thunnus-family. However, it’s so tuna-like that it is considered tuna. The Skipjack is the smallest of the tuna, but not with the same diet as the others. They can’t inhale their prey in like the rest.
The name comes from the lively act the Skipjack can perform, jumping out of the water and splashing water around.
A mature Skipjack is 40 cm long and weighs abt. 1,8 kg.
Balaya, Striped tuna, Tongkol, Arctic bonito, Aku, Katsu mushmouth, Oceanic bonito or Victor fish.
AGE, SIZE & WEIGHT
Skipjack develops quickly in size and weight. At a mature 8-12 years they weigh 8-10 kg. The maximum reported weight is 34,5 kg with a maximum reported age of 12 years. A one year old Skipjack is estimated to be 31 cm long and weighs ca. 1,8 kg while a full mature Skipjack is 40 cm in length.
Pacific Ocean, Indian Ocean & Atlantic Ocean
Skipjack tuna likes warm water (>28-29°C) and typically dives no deeper than 100 meters and often appears on the surface, hence the name. Skipjack is a lively fish and a fast swimmer. They exhibit a strong tendency to school in surface waters with birds, drifting objects, sharks, whales and may show a characteristic behaviour like jumping, feeding, foaming, etc.
As Skipjack tuna cannot inhale food like other tuna so they have to hunt their prey with their speed. The normal meal is varies between small fish, squid, pelagic crustaceans and other small invertebrates.
The reproduction rate of Skipjack tuna is high, as they start spawning after 1-2 years. At that time Skipjack has reached a size of about 40 cm and a weight of 1,8 kg. The females spawn the whole year round with increased activities in certain periods. The females spawn 0,8-2 million eggs per year, depending on the state of the female body and the nutrition of the waters they swim in. The males fertilise the eggs by releasing their sperm at the same time as the females are spawning. This increases the fertilisation rate. Unfortunately, predators eat a large part of the eggs.
This tuna has a lower commercial value and as Skipjack tuna is often swimming in large schools, they’re targeted by tuna purse seiners and pole & line vessels.
General used for the tuna canning industry, where quality is not the most important factor for the processors. Due to its nutrient high quality Skipjack is used in Japan for the production of Katsuobushi (dried for soup, dishes and sauces), but also as bait for swordfish.