We've been seeing this for years....

[senoritafish]

"Researchers have found that as fishermen hauled away the biggest fish, cod became smaller and produced smaller offspring. It's a rule every weekend angler knows: Throw back the small fish. It helps the population survive long term. Right? Wrong. Mounting evidence suggests that by harvesting only the biggest fish - or biggest mammals, for that matter - mankind is unwittingly forcing many species to evolve rapidly. This process, called "contemporary evolution," isn't taking place over centuries. It's on a fast track that can happen within a few decades."

http://www.csmonitor.com/2004/0520/p15s01-sten.html

It's why for quite a few species, there are regulations for "slot limits" - i.e. you can only take animals bigger than a certain size (so hopefully, they'll have had a chance to spawn at least once), and smaller than the largest sizes, leaving the really large animals that produce the most eggs. However, if all the largest animals are already gone.....

Comments

[aliki.livejournal.com]

Good post.. I was talking about this the other day with some recreational fishermen, explaining how at any given age, say, 7 years old, the size of a striped bass ranges from 24" to 29"... but if the size limits on fishing is 26", you'll consistently be keeping *smaller* 7-year olds and allowing those small runts to reproduce, while selectively harvesting the bigger ones.

Light bulbs went off in their heads. They were fascinated by the concept.

[senoritafish.livejournal.com]

It seems to take a while before it sinks in sometimes though. Like when Frances Clarke (a biologist in California) kept warning that sardines were going crash, at least 20 years before they actually did.

You know, I meant to answer this right after you posted it. I know you'll have been very busy the last few weeks, so maybe you won't see this right away, but thanks for adding me.

It's always amazing to me when people add me first.

And congratulations. :)