Tuesday, November 15, 2016

How Long Do They Live?

In the last few weeks I have often been asked how long does that fish live? While I am not an expert on the phylum Chordata (Fish both boney (osteichthyes) and cartilaginous fish like sharks and rays (chondrichthyes), I will demonstrate that the answer is very subjective depending on the specie we are talking about.

Most often this question is asked while I am describing the life of Parrot Fish. Most parrot fish start out life with both male and female sex organs. Beginning as a female they mature and become a male as their production as a female ceases. At this point they also change appearance into the bright beautiful parrot fish we commonly identify with.

Female Stop Light

Male Stop Light

Female Queen
Male Queen

The above pictures courtesy of public domain internet access.

While most parrot fish go through this metamorphosis not all do. The marble parrotfish, for example stays the same sex through out it's life.

Studies demonstrate that and actively reproducing female parrot fish will not change sex. This suggests tat while they are actively producing estrogen they cannot make the change. On the other hand testing that injected testosterone into female parrot fish did induce the change. So the question is unanswered. Is it a failure to produce estrogen or another trigger that jump starts the production of testosterone that makes male characteristics become dominant? I am sure that Chordata experts will eventually answer this question but for now I will continue to ponder it.

Back to the life span of fish. Generally, the larger the specie the longer it will live. Here are some examples:
  • Small fish like blennies live 1 to 3 years.
  • Parrot fish, a more medium sized specie live 5 to 7 years.
  • Larger specie like tarpon live 50 to 60 years.
Some of you will inevitably ask about sharks. Sharks live about 20 to 30 years but this to is subjective. The Greenland Shark lives around 400 years. It doesn't even reach sexual maturity until it is 150 years old. After raising 2 kids, I doubt most of us would survive an adolescent stage lasting this long in our children.

For most of you that ask this question the answer is 5 to 7 years. Remember the answer needs to be more specific and I will gladly research the answer for your favorite specie.

Until next time always make your total number of ascents equal your total number of descents.
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