Life Cycle of Tuna

Most tuna species can live for 15 years and somtimes up to 20 years. Like many other fishes, tuna fish are migratory. They are known to swim throughout the oceans in the world. What do they do in their lifetime? Let's learn more!

                                                                  Illustration of Tuna Life Cycle

Surprisingly, tuna often lay eggs in the open water and their life begin and end in the same spawning place. (Just like salmon, tuna tend to return to the same area where they were born.)  In a single spawning, a female tuna fish can lay 6,000,000 eggs and number of eggs that tuna fish can spawn is relative to its size. For example, a smaller fish tuna may yield fewer eggs than a larger one.  

After female tuna lay eggs, males fertilize them by spreading their sperm in the water nearby where the eggs are laid. The eggs usually hatch about 4 days after fertilization. Out of millions of eggs, only about two or three tuna become adult fish. Other eggs and juvenile fish are often eaten by predators such as sea birds and bigger fish and even by the tuna fish of same kind.

As they grow, the fearless young and juvenile tuna fish migrate around the ocean looking for food and they usually move as a group to avoid being attacked by larger fish. Some of them are eaten by predators or caught by fishermen before becoming adult fish. Among those tuna fish that successfully reached full maturity may enjoy being on the top of the food chain in the ocean until they are caught by fishermen and brought to our dinner table.
Lastly, mature female tuna fish will return to spawning area and release eggs. Male Tuna will release sperm to fertilize the eggs and life of tuna begins once again.

                                                    Young tuna often move as a school to avoid predators

                                                                   Juvenile Yellowfin Tuna caught in Gulf of Mexico.

 

Now we have learned about the life cycle of Tuna, let's investigate how climate change would have an impact on their life? Does warmer temperature help the most tuna species? Are they suffering from climate change? Let's learn more in the next section "climate change and range shift", but before we do this, it is not a bad idea to have background knowledge about the islands where the climate change is influencing the tuna species!

References

1. All About a Tuna’s Life 2012. Bumble Bee Foods, LL <http://www.bumblebee.com/about/seafood-school/life>

2. NOAA Irons Tuna Quota. Mike Crowe and Staff. Fishermen’s voice: News and Comments for and by the fishermen of Marine. January 2011 <http://www.fishermensvoice.com/archives/0111index.html>

*Photos used above were taken from the following websites:

1) bioweb,uwlax.edu : Life Cycle of Tuna (illustration)

2) aquaculturehub.org : Yellowfin Tuna Eggs 14 Hours after Fertilization

3) fadio.ird.fr : Young tuna often move as a shcool to avoid predators.

4) www.obxguides.com : Juvenile Yellowfin Tuna caught in Gulf of Mexico