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Learn About Tuna

Tuna is a family of saltwater predatory fish that comes in a variety of species.  Size varies by specie as does the range of flesh colour and intensity of flavour.  The flavour of tuna tends to be mild, which explains why kids tend to like it better than salmon.  Tuna are among the fastest swimming fish in the sea.  People have valued tuna as a favourite food source for centuries, but most of us know very little about this diverse and agile creature found in all the world's oceans.


Tuna is managed by 5 Regional Fisheries Management Organizations (RFMOs):

  • Western Atlantic Ocean
  • Eastern Atlantic Ocean
  • Indian Ocean
  • Eastern pacific Ocean
  • Western pacific Ocean


Tuna are among the most beautiful of the sea’s creatures.  These fish, with their delicate colours and wonderfully streamlined bodies, have evolved to what appears to be the limit of hydrodynamic refinement.  When tuna swim rapidly their fins retract into grooves; even their eyes form a smooth surface with the rest of their head.


Tuna live in the open sea rather than near the shore.  For the most part, they stay in the upper layer of water called the mixed layer.  The mixed layer is warmed by the sun and air, stirred by the wind and waves, and is a rich environment for tuna.  Tuna reside in warm water.  The Skipjack tuna, for example, is confined for the most part in water at 25 degrees celsius (78 degrees Fahrenheit) or warmer.


Tuna travel. They are nomads and move across entire oceans. By scientific tagging, Albacore tuna have been tracked over 8,500 km from California to Japan at the rate of 25 km per day.


Tuna never rest; they must always be moving.  To get enough oxygen they must move one body length per second.  Tuna get their oxygen from water, not from the air.  They swim with their mouth open, which shoots a jet of water over their gills with which they extract oxygen from the water.  Because of this system, they must remain swimming and can never stand still.


This constant physical action also creates an enormous demand for energy and a need to eat large quantities of food.  A typical tuna may eat one-quarter its own weight in food in one day!  The daily menu for tuna includes fishes, crustaceans and mollusks.  The Skipjack tuna is not picky about its diet, and neither are its many tuna cousins.  They will eat whatever is available.


Tuna are not cold-blooded as most fish, but have a system whereby they maintain their temperature a few degrees warmer than the water. As warm blood returns to the gills to get more oxygen, it passes close to cooler blood coming from the gills. As they pass, the warmth is transferred to the cooler oxygen-rich blood.


Like all creatures, tuna have a camouflage against their natural predators.  From deep in the water, looking up, the light-coloured belly of tuna blends with the surface light and makes the fish hard to see. Looking down into the water, you don't see the tuna, because their back is blue, and blends with the deep blue of the sea.


Tuna begin life when a female lays her eggs (in fish, this is called spawning) in the open water. (While tuna and tuna-like fishes are at home almost anywhere in the world, it is interesting that they return to the same general locality for spawning.).  The eggs are fertilized by males who release their sperm in the water where the eggs have been laid.  Very small larvae hatch from the eggs usually within 24 hours.  One large female may lay as many as 6,000,000 eggs in a single spawning.  The number of eggs laid is related to size of the fish; a smaller female may yield only a million eggs.  The eggs can be considered tiny: they measure one mm (0.04 inches) in diameter at spawning, including the droplet of oil surrounding the egg which makes them buoyant. From hatching to full growth, some of these species increase their size one billion times. If these fish lay so many eggs, why are the oceans not clogged with them?  Actually, out of the millions of eggs spawned by tuna only about two, on average, grow to maturity from a single female.  What happened to all those eggs, larvae, juveniles and young fish?  They were eaten by bigger fish, even by their own kind.  They also become food for many other kinds of swimmers in the sea as well as sea birds.  Those who escape the perils of being eaten and grow into adults will find themselves at the top of the food chain with few other swimmers to threaten them.


The more marine biologists have learned about tuna, the greater the mysteries surrounding these remarkable fish. Some of the unresolved questions are: How do the tuna navigate over thousands of miles in the trackless wilderness of the open ocean? To what extent are they homoeothermic – that is, able to maintain a roughly-constant temperature above that of the water in which they live? Why do the female tuna lay such enormous quantities of eggs? How do adult tuna, living at times in the desert waters of the high seas, obtain the quantities of food they need to swim continuously? As time continues forward, we can only hope researches will be able to find the answers about these nomads, the tuna. 


The three methods of commercially catching tuna include:


 A seine or net is drawn out from the fishing boat and around the school of tuna.  Weights carry one edge of the seine      deep into the water.  When the fish are surrounded, the bottom of the seine is drawn together or pursed, so that the fish are trapped and hauled aboard the boat.  This method accounts for about 80 percent of commercially- caught Light Meat Tuna.  The tuna packed for BRUNSWICK® is a light meat tuna.


A very long line (as much as 130 km or 81 m) supported by floats and marked with flags is set out from a fishing boat.  Branch lines attached to the long line are sunk with baited hooks to depths of 55 to 150 meters.  It may take as many as 20 hours to set a line and longer to retrieve it with its catch.  Long-lining accounts for about 80 percent of the world's Albacore tuna harvest.


Live bait (anchovies or sardines) are dumped from the fishing boat to bring tuna into a feeding frenzy.  This is called "chumming".  Fishermen on the boat drop lines with barbless hooks into the school of fish, and bring them aboard as they are hooked.





Tuna is delivered to the cannery either directly from the fishing vessel or from freezer ships delivering from foreign fishing companies.  The majority of the tuna delivered is frozen.  To maintain quality it is moved promptly from the vessel into cold storage facilities at the cannery. 


During the unloading, the fish is "sized" which keeps fish of the same size and weight together. This helps ensure quality during the thawing and precooking process.


The processing starts with tuna being moved from the freezer to thawing tanks.  These are large water tanks where the tuna is uniformly thawed prior to the initial cleaning of the tuna.


The thawed tuna is then loaded onto metal racks which are wheeled into large steam pressure-cooking chambers called retorts.  Tuna is baked (precooked) for a prescribed time and temperature, depending on the size of the fish.  This steam precook removes the natural tuna oil, which is too strong in flavour to remain in the fish, and prepares the tuna for the easy removal of skin and bones.


After the precook the racks of tuna are moved to a temperature-controlled room for cooling.


Once the tuna is cooled, it is sent to the cleaning tables where the edible meat is removed from skin and bones.


The cleaned loins are then moved to the canning process.  Cans are automatically filled with tuna and move in a single line from the filling machine towards the vacuum sealer. Next, the cans of tuna automatically receive the appropriate measure of salt, vegetable broth, water or oil, depending on the style of pack.  Lids are then automatically clinched on the top of the can before entering the vacuum sealer, where the air is withdrawn and the lid hermetically sealed.


The cans proceed through a water bath to clean off oil residue and then are placed back into retort baskets.  After the prescribed cook time and temperature, the sterilized canned tuna is removed from the retort and moved to a cooling area.


When the cans have cooled they are labeled and packed in cartons.


The day following packing, quality control personnel cut open representative samples from the previous day’s pack and grade them for the following: vacuum, appearance, smell, texture, style of pack, cleanliness, and flavour.  The results of the cuttings determine the quality of the product. Throughout the entire processing, quality control measures are exercised to maintain the standards that result in a quality product.  BRUNSWICK® Tuna is recognized as a high quality product by the trade, consumers and competitors.


After receiving Quality Assurance approval, the tuna is ready to be loaded onto containers and shipped to market.


 MAKE IT GREAT MAKE IT BRUNSWICK® TUNA” is not just a tagline, it’s our commitment to you. BRUNSWICK® offers a variety of canned seafood products, and although canning and cooking methods vary from one product to another, they must all pass strict quality control measures before they earn the privilege of wearing the BRUNSWICK® label. You can expect great looking, great tasting products – can after can after can. That’s because our Quality Assurance team makes sure they meet the industry leading standards we have set for our products.  Only on their approval does the product get shipped to the warehouse, the marketplace, and your table.  Routine regulatory audits confirm this high level of product safety and quality, year after year.

An integral component of BRUNSWICK® Quality Assurance is our intensive supplier and product assessment program.  BRUNSWICK® will only source product from manufacturing facilities that meet or exceed our company standards.  In fact, BRUNSWICK® is the only marketer of canned seafood products in Canada that has full time quality assurance and procurement staff in South East Asia, where the majority of tuna and specialty products are sourced, leading to greater assurance of product quality and safety. All manufacturing facilities supplying BRUNSWICK® products must operate under internationally recognized Hazard Analysis Critical Control Point (HACCP) food safety principles.  All facilities are routinely put through a rigorous inspection to ensure that they continue to measure up to our standards. Any facilities that do not meet these standards are no longer permitted to supply products that will bear the BRUNSWICK® name.

Achieving the desired results is accomplished by utilizing the expertise of BRUNSWICK® Technical Services and Quality Assurance departments. This team is comprised of

  •         Thermal process specialists
  •         Food scientists
  •         Certified sensory graders
  •         Process engineers
  •         Packaging specialists
  •         HACCP trained Auditors


The combination of industry experience, science based quality assurance systems and inspection throughout the life cycle of our products is your guarantee of the safety and high quality you’ve come to expect from a brand leader like BRUNSWICK®!

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