Tuna is one of the most eaten fish in the world. There are 8 species of this subgroup, which is in the mackerel family and ranges in size and color. Tuna is a nomadic species and is found throughout the worlds oceans. It can be eaten fresh or canned. People usually eat tuna loin raw or seared with light seasoning. On the other hand, canned tuna is cooked for a long time and is usually served with a lot of seasoning.
What is Tuna Fish Made Out Of? A Deep Dive into the Composition of This Hearty Fish
Tuna fish – it’s one of the most popular types of seafood in the world. Its meaty texture, savory flavor, and stellar nutritional profile make it a pantry staple for many. But have you ever stopped to think about what exactly makes up this powerhouse protein? Let’s take a deeper look at the composition of tuna fish.
Tuna Belongs to the Fish Family Scombridae
First things first – tuna is a fish! More specifically, it belongs to the family Scombridae, which includes other fast-swimming, predatory fish like mackerels and bonitos The most commonly eaten tuna species are
- Albacore (Thunnus alalunga)
- Yellowfin (Thunnus albacares)
- Bigeye (Thunnus obesus)
- Bluefin (Thunnus thynnus)
- Skipjack (Katsuwonus pelamis)
These fish have streamlined, torpedo-shaped bodies that make them excellent swimmers. Their powerful tail fins and fins along the back propel them through the water at lightning fast speeds. Tuna are highly migratory and can cross entire oceans in their lifetimes.
Muscle Tissue Makes Up the Bulk of a Tuna’s Body
The main component of a tuna is skeletal muscle. Unlike mammals and birds, the muscle tissue of tuna is not white – it’s red. This is because tuna muscles contain higher levels of myoglobin, an oxygen-binding protein that gives them their characteristic dark red color.
Tuna muscle is arranged in sequential cone-shaped bands along the fish’s body, This allows maximum transfer of force and power as the muscles contract to propel the tuna forward The tender flaky meat that we eat from tunas is composed of these muscle bands layered one after another
Next come the fins – tuna have a number of fins that provide stability and allow precise control as they speed through the water. Their rigid spiny dorsal and anal fins can be tucked into grooves on the body to reduce drag. The lunate tail fin is responsible for powerful forward propulsion. Pectoral fins on the sides steer and act as hydrofoils.
Other parts that make up a tuna’s anatomy include their eyes, gills, heart, stomach, intestines, liver, kidneys, spleen and reproductive organs. Tuna also have an organ called the rete mirabile that allows them to keep certain areas like the muscles, eyes and brain warmer than the surrounding water temperature.
Tuna Have an Extremely Efficient Circulatory System
One of the most unique things about tuna is their circulatory system. To keep up with their high-performance metabolism, tuna need extra oxygen delivered to their muscles and other vital organs.
They achieve this through a network of blood vessels called the rete mirabile, which allows cooler venous blood returning from the body to transfer its heat to the arterial blood headed to the organs before reaching the gills. This allows tuna to keep the temperature of their life-sustaining organs elevated above the surrounding water.
The tuna heart is another marvel of efficiency. It pumps blood at an amazing pressure and can handle huge volumes – a large bluefin’s heart may pump 25-30 liters per minute! This allows greater diffusion of oxygen at the gills and supports the tuna’s active, fast lifestyle.
Tuna Need a Lot of Energy to Maintain Their Speed
The speed and power of tunas don’t come without costs – these fish have extremely high energy demands. Their muscles need large amounts of oxygen and nutrients to perform at such a high level for extended periods.
To meet these needs, tunas have to eat a lot! An average tuna may consume 8-10% of its body weight in prey each day. They use their speed and specially adapted eyesight to hunt down schools of fish like mackerel, herring and anchovies as well as squid and crustaceans.
All this food provides tuna with the proteins, fats, vitamins and minerals they need to maintain their active metabolism and keep swimming immense distances. The high calorie density of their prey allows tuna to build up fat deposits that can sustain them over long migrations.
Tuna Nutrition: A Lean Source of Protein, Omega-3s and Vitamins
When we eat tuna, we gain access to all the beneficial compounds they accumulate from the prey in their diets. Here’s a quick look at some of the key nutrients found in tuna:
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High-quality lean protein – tuna is an excellent source of protein with all the essential amino acids. A 3 oz serving can provide 20-25 grams.
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Omega-3 fatty acids – tuna contain anti-inflammatory omega-3s like EPA and DHA.
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Vitamin B12 – tuna is one of the richest food sources of this important vitamin.
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Selenium – tuna provide this essential mineral which acts as an antioxidant.
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Niacin, vitamin B6 and other B-vitamins.
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Important minerals like potassium, iron and zinc.
The five main species of tuna
Name in Latin: Katsuwonus pelamis; largest weight: 35 kg; unique traits: not in the Thunnus genus but a related species Superpower: It has the fastest reproduction rate and the largest stocks of all tuna. Use: Canned/tinned.
Latin name: Thunnus alalongaMaximum weight: 60 kg Distinguishing features: Long pectoral fins. Superpower: Has a high protein diet: eats only octopus and squid. Use: Fresh and in cans. Albacore preserved in olive oil is delicious in salads.
Latin name: Thunnus albacares Maximum weight: 175 kg Distinguishing features: Bright yellow fins and finlets. Big fish: Yellowfin tuna and dolphins hang out together in the East Pacific, close to the west coast of Central America. Schools of tuna swim around 100 to 150 metres beneath schools of dolphins. The reasons for this are not entirely understood.
Use: Fresh, canned/tinned. Yellowfin’s mild flavour makes it great in steak form.
The Atlantic bluefin tuna is Thunnus thynnus, the Pacific bluefin tuna is Thunnus orientalis, and the Southern bluefin tuna is Thunnus maccoyii. They can weigh up to 700 kg and are known as “the giant among tuna.” However, it grows very slowly and doesn’t reproduce until it has reached an advanced age. Superpower: It’s as large and fast as a small car.
Sashimi or sushi: As of 2021, only two bluefin tuna fisheries have met the MSC’s strict standards for sustainable fishing. You can only get their catch in Japan and France.
Latin name: Thunnus obesusMaximum weight: 210 kg Distinguishing features: Big eyes. Its superpower is that it is a diurnal vertical migrant, which means that it can move up to 500 meters in a day. The fat layer formed to protect it from cold keeps its flesh juicy.
Use: Sashimi, “white beef”
Tuna carrying the blue MSC label is certified sustainable. MSC labelled tuna comes from a fishery that has been independently assessed to the MSC Fisheries Standard. The MSC Chain of Custody Standard says that all businesses that handle MSC seafood must follow it. This makes sure that fish and seafood with the blue label came from fishing that was certified as sustainable by the MSC Fisheries Standard.
Tuna is most commonly canned but loins can also be purchased fresh or frozen. Canned, fresh and frozen MSC labelled tuna products can be found throughout the world.
Choose the right tuna for your dish
Skipjack is the most popular type of tuna sold around the world because it is the most common type of tuna in the ocean and makes up 60% of the global tuna catch. If you’re in Europe or Asia, skipjack is the tuna species most likely found in tins. 50% of skipjack tuna stocks are found in the Western Central South Pacific Ocean.
As well as skipjack there are four other main species of tuna include albacore, bigeye, bluefin and yellowfin. Choose the right tuna fish for your dish, just like you would choose a different type of vegetable or a different breed of cow.