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The bluefin tuna inhabit the pelagic ecosystem of the entire North Atlantic and its adjacent seas, primarily the Mediterranean Sea, North of Norway and from the Black Sea to the Gulf of Mexico.

The Atlantic Bluefin Tuna (ABFT) occupies the surface and subsurface waters of the coastal and open-sea areas. However, both jucenile and adult ABFT frequently dive to depth of 500-1000m.

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In Mediterranean Sea, ABFT reproduce for the first time between ages of 3–5 years.

Oviparous batch spawners when sea surface reach 22.5-25 degrees (Mediterranean) between june and August.

13-15 million eggs.

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The Atlantic Bluefin Tuna can been >3 m in length and weigh up to 900 kg.

The Atlantic bluefin tuna can sustain temperature down to 3 °C as well as up to 30 °C, while maintaining a stable internal body temperature.

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Migration patterns during breeding for Thermoregulation in the gulf of mexico

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Migration patterns during breeding for Thermoregulation in the gulf of mexico

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The Bluefin tuna perform vertical migrations during the breeding phase in the Gulf of mexico.

The Bluefin Tuna dives to daily depths of 500+/- 150m and exhibits directed movement paths to and from localized breeding areas. This depth is shallower during the night when Bluefin tuna perform oscillatory dives with 200 +/- 76m depth.

These dives are suggests behaviorally and physiological thermoregulation in the gulf of mexico due to the Bluefin tuna being Ectothermic.

Article Link:

https://rdcu.be/dF71F

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Migration follow prey migration patterns (herring, macrell, and squid)

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Migration follow prey migration patterns (herring, macrell, and squid)

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Seasonal Movements, Aggregations and Diving Behavior of Atlantic Bluefin Tuna (Thunnus thynnus) Revealed with Archival Tags

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Electronic tags were used to examine the seasonal movements, aggregations and diving behaviors of Atlantic bluefin tuna (Thunnus thynnus) to better understand their migration ecology and oceanic habitat utilization. Implantable archival tags (n = 561) were deployed in bluefin tuna from 1996 to 2005 and 106 tags were recovered. Movement paths of the fish were reconstructed using light level and sea-surface-temperature-based geolocation estimates. To quantify habitat utilization we employed a weighted kernel estimation technique that removed the biases of deployment location and track length. Throughout the North Atlantic, high residence times (167±33 days) were identified in four spatially confined regions on a seasonal scale. Within each region, bluefin tuna experienced distinct temperature regimes and displayed different diving behaviors. The mean diving depths within the high-use areas were significantly shallower and the dive frequency and the variance in internal temperature significantly higher than during transit movements between the high-use areas. Residence time in the more northern latitude high-use areas was significantly correlated with levels of primary productivity. The regions of aggregation are associated with areas of abundant prey and potentially represent critical foraging habitats that have seasonally abundant prey. Throughout the North Atlantic mean diving depth was significantly correlated with the depth of the thermocline, and dive behavior changed in relation to the stratification of the water column. In this study, with numerous multi-year tracks, there appear to be repeatable patterns of clear aggregation areas that potentially are changing with environmental conditions. The high concentrations of bluefin tuna in predictable locations indicate that Atlantic bluefin tuna are vulnerable to concentrated fishing efforts in the regions of foraging aggregations.

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Eggs hatch after 2 days.

At 24°C, embryo development lasts about 32 hours and larval stages about 30 days.

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Ram ventilators, means they don’t have the ability to pump water through their gills, and have to keep swimming to get sufficient amount of oxygen.

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Atlantic bluefin tuna is belived to have two main spawning grounds in the gulf of Mexico and in the Mediterranean sea. 

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Atlantic bluefin tuna is belived to have two main spawning grounds in the gulf of Mexico and in the Mediterranean sea. 

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Slope sea is also a spawning ground for Atlantic tuna

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Slope sea is also a spawning ground for Atlantic tuna

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The adult atlantic Bluefin tuna populations spawn in three major proven locations which includes the Mediterranean, Gulf of Mexico and Slope Sea outside the United states.

Their migration makes research difficult which is important to manage their populations.

Younger western bluefin tuna spawn in the slope sea until they reach a certain size where longer migrations to the GOM is possible (gulf of mexico). The spawning tuna in the Slope sea is estimated to have higher biomass compared to older tuna in the GOM, further strengthened by larval abundances in the slope sea, suggesting the region as a third major spawning ground.

Article link:

https://cdnsciencepub.com/doi/full/10.1139/cjfas-2020-0444

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Experiments in captivity suggest that spawning by an individual might occur only once every 2 or 3 years

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Comeback of Atlantic Bluefin Tuna in Norwegian waters 

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Comeback of Atlantic Bluefin Tuna in Norwegian waters 

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Bluefin tuna has reestablished in Norway, echibiting its historical migration pattern in Norwegian waters in recet years after being absent for decades

Bluefin tuna har been feeding along the Norwegian coastline and in offshore waters for thousands of years due to high abundance of nutrient-rich schooling prey such as

- Mackerel

- Herring

- Blue whiting

- Lesser sandeel

Historically BFT visited Norwegian waters from early July until late October to feed.

During feeding season majority of individuals were adults (50-520kg)

There was a drastic reduction in the distribiution and extent of BFT migration patterns in Norwegian waters from ca 1965 onwards --> led to gradual decline of the Norwegian BFT fishery.

Reasons for reduction:

Uncertain however..

major international overfishing (juvenile and adult fish) ocurring for decades --> possible potential reason for historical decline on BFT in Norwegian waters

Overfishing of juvenile in spawning areas in the Mediterranean Sea, Bay of Biscay and off the coast of western Africa

=== Possible effect on the migration pattern by interactions between environmental, trophic and fishing processes

Discussion part of the article

A significant increase in the number of BFT observations in Norwegian waters from 2012 to 2018 + the latitudinal distribution of observations has widened each year between 2016 and 2018

The comeback coincides with the overall annual increase in BFT spawning stock biomass (SSB) observed during feeding and long-distance migration events.

Large BFT found in Norwegian waters may be due to different factors:

Sea surface temperature (SST) tolerance (small juvenile BFT may not tolerate low SST)

Long distance migration of food (herring, mackerel and capelin) has a function of fish length --> increase in body size will determine and increase the extent of migration = food availability is important for the maintenance of growth and body temperature

BFT seemed to mainly prey on mackerel. Mackerel have expanded their northern distribution in the in the recent years Northeast Atlantic --> important food source for BFT = tuna follow mackerels migration patterns and therefore expand their own northern distribution.

Link: https://www.sciencedirect.com/science/article/pii/S016578362030206X

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Bluefin tuna is one of the fastest fish in the pelagic ocean (75-100km/h). Torpedo schapped body reaching well over 3m long

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Authors

Insha Ahmed Taray Department of Aerospace Engineering, Faculty of Engineering,Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia

Azmin Shakrine Mohd Rafie Department of Aerospace Engineering, Faculty of Engineering,Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia

Mohammad Zuber Department of Aeronautical & Automobile Engineering, MIT, Manipal University, Manipal 576104, Karnataka, India

Kamarul Arifin Ahmad Department of Aerospace Engineering, Faculty of Engineering,Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia

Keywords:
Bluefin Tuna, Hydrodynamics, Thunniform locomotion, Propulsive efficiency, Undulatory Propulsion

Abstract

In the recent years, the study of unconventional fish-like bodies has been growing with the purpose of developing more efficient under-water vehicles; inspiration from nature to emulate these life forms to understand their propulsion system and to attain superior manoeuvring has given birth to the field of aquatic Biomimetics. Because of their remarkable capabilities, fish have shown extraordinary adaptation towards underwater locomotion which naturally has led to the sense of curiosity among engineers. A limited number of works has been published on bluefin tuna which is considered the largest Tuna species and the largest bony fish in ocean, weighing over 540 kilograms with length reaching over 3.05 metersand with a lifespan of 30 years. This fish has evolved overtime in terms of high-speed (reaching 75-100 km/hour), making it one of the fastest fish that swims in pelagic zone of oceans. Their torpedo shaped body is the most hydrodynamically efficient shape possible, making them the ultimate fish. This paper presents an overview of literature studies done exclusively and relevant to bluefin tuna. The review is divided into following sections: (I) Introduction(to swimming classification), (II) Thunniform Locomotion, (III) Undulatory Motion and Propulsion, (IV) Energy Efficiency and Energy Extraction, and (V) Computational Studies. The review highlights that this riveting fish is not only fastest but also, warm-blooded unlike any other fish that dives in pelagic zone and how that contributes to its high-speed. This paper aims to show that thunniform locomotion, with an emphasis on the lunate tail propulsion, is the most efficient locomotion only attained by super-advanced fish, and highlights the propulsive efficiency of thunniform motion which reaches about 70%, and the energy saving techniques adopted by bluefin tuna to make it the most efficient engine created by nature.

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Hydrodynamics of Bluefin Tuna - A Review

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Insha Ahmed Taray Department of Aerospace Engineering, Faculty of Engineering,Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia Azmin Shakrine Mohd Rafie Department of Aerospace Engineering, Faculty of Engineering,Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia Mohammad Zuber Department of Aeronautical & Automobile Engineering, MIT, Manipal University,

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Figure 1:

Spatial distribution of Atlantic bluefin tuna (gray shading) and main migration routes (black arrows) are deduced from current and historical fisheries data as well as traditional and electronic tagging information (see text for references). The vertical dashed dotted line depicts the stock delimitation between the two current ICCAT management units. The main spawning grounds (dark dotted gray areas) being currently assumed in the literature are located in the Mediterranean Sea and the Gulf of Mexico.

Source: https://doi.org/10.1111/j.1467-2979.2005.00197.x

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The International Commission for the Conservation of Atlantic Tunas; ICCAT

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The International Commission for the Conservation of Atlantic Tunas; ICCAT

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Management of Northeast Atlantic bluefin tuna have been done as a collaboration, because the species are highly mobile.

Source: Adrian W. Leach, Polina Levontin, Johnson Holt, Laurence T. Kell, John D. Mumford,

Identification and prioritization of uncertainties for management of Eastern Atlantic bluefin tuna (Thunnus thynnus),

https://doi.org/10.1016/j.marpol.2014.03.010.

(https://www.sciencedirect.com/science/article/pii/S0308597X14000827)

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Leif Asbjørn Vøllestad (Universitetet i Oslo)

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Makrellstørje er den største av artene i makrellfamilien og kan bli opptil 4,5 meter lang. Den er en rask svømmer, og det er målt svømmehastighet på 66 kilometer i timen. Den blir ofte kalt tunfisk eller blåfinnet tunfisk. Hardt fiske har ført til at bestandene har vært overbeskattet.