Tuna

This might be a silly blog post but, I thought some of you might be interested. Earlier this week we bought some canned tuna and so I started thinking about the actual fish and wanted to learn about it. So I did a Google search and read all about tuna. I don’t know if it’s the biologist in me or if everybody will find it interesting so I’m  going to share a few of the things I learned with you here.

I’m going off memory so I hope it’s fairly accurate.

The blue fin tuna can swim 55 mph. Which I think is the fastest of any fish. If I remember correctly.

Another interesting thing about tuna is they maintain an internal temperature of over 90°F even in water as cold as 40°F or thereabouts.

It is due to an amazing countercurrent heat exchange system in the blood vessels. I do remember learning this as an undergraduate in biology. I don’t remember the details but it has something to do with the way the veins and arteries are close together and transfer heat with blood flow in opposite direction. The cold oxygenated blood in the arteries collects the heat from the warm deoxygenated blood leaving the muscles through veins. I think. J

The blue fin tuna has a large heart and high blood volume. Along with the warm body temperature this allows faster nerve impulses and therefore muscles respond faster which is why they’re so quick. I’m also wondering if that’s not why their flesh is pink or red compared with most fish which is white. The extra hemoglobin?

The only predator that can catch a blue fin tuna is the mako shark and killer whale. And man of course.

A single blue fin tuna was sold at auction to a Japanese buyer earlier this month for an average of $3600 per pound. I believe the fish weighed about 500 pounds and sold for approximately $1.8 million. I can’t help but wonder if this is not a publicity stunt. Can he actually recoup $3600 per pound? Maybe in Japan I guess.

Blue fin tuna can weigh up to 1500-2000 pounds. And live as long as 40 years.  Although now, it is rare to find a blue fin tuna that big because of overfishing. Most of the tuna caught nowadays is about 5 to 7 years old, I believe. I think the old ones can be about 10 feet long.

The blue fin tuna population has gone down 96.4% or thereabouts since commercial fishing began decades ago. They are on the verge of extinction. To clarify that means that for every 100 Pacific Bluefin tuna that were in the ocean a few decades ago now there are only 3.6.

Of course there are other tuna species such as yellowfin and albacore. They don’t get nearly as big. I don’t know which species of tuna are endangered or near extinction. But I do know that they have been fished extensively. I think Japan consumes 80% of all the tuna that is caught commercially.

I believe there have been efforts to farm tuna but I don’t think they have been very successful.

Tuna travel extensively. To maintain oxygen levels they are constantly swimming. They migrate across oceans—thousands of miles yearly.

I know this is mostly about blue fin tuna but they are the most interesting to me. I didn’t really do much research --just read a few articles. So take these facts with a grain of salt. Some of them are probably wrong. I’m not getting graded on this so it’s not the most well-written article -- it’s just for fun. But anyway I thought was interesting so I wanted to share.

That’s my two cents