Sorry, Charlie
Ever wonder why tuna is such a tough fish to catch?
Three reasons: first of all, a tuna has
the temperament of "an armadillo in a hole." It just doesn't
want to come out and play.
Secondly, a tuna has no body fat: it all muscle, bone,
skin, and yucky stuff. Therefore, pound-for-pound, a tuna has more muscle
than a fish with fat.
Third reason? This is the most interesting: a tuna is
one of a small handful of WARM-BLOODED salt water fish! Yes, although
it's a fish, not a mammal, a tuna is warm-blooded! It's body temperature
operates at approximately 10-20 degrees warmer than a cold-blooded fish...and
therefore, it's muscles are more efficient.
Therefore, when compared to another kind of fish of identical
weight, a tuna is generally harder to pull in.
Source: Bely, P. & Bely, S. (2007). Do dolphins ever sleep? 211
questions and answers about ships, the sky and the sea. Dobbs Ferry,
NY: Sheridan House, Inc.