Subject: Re: NANFA-L-- Review of Suckers in North America
From: Todd Crail (farmertodd at buckeye-express.com)
Date: Tue Oct 12 2004 - 09:34:20 CDT
> ----- Original Message -----
> From: Moontanman at aol.com
> Is there any theories about why this happens?
Great question. I think a lot of times we view this as a predation type
thing, and I think we're missing the greatest cause of mortality. Rearing
the animals to a certain size in captivity is great because it takes out a
large percentage of the predators by size... I'm sure there's a lowered
mortality curve the further along you've developed the animals. But what we
forget about is that a _specimen's_ greatest competitor is it's own
They compete for the same food, the same habitat, the same cover from
predators, the same mates, unlike with other species, which have _at least_
one resource separating their survival success.
Predators really only clean up the scraps from the loosers in Intraspecific
competition (competition within a species). That is to say, by rearing in
captivity, even though we've paid plenty of attention to making the
spawnings as random as possible, paying attention to collecting from the
largest amount of alleles across the population, genetically "making sure"
that you've included the highest possible amount of survival success...
You've still completely removed the whole dimension of Intraspecific
interactions that have a more profound effect on who is left weak, without
the best cover, etc etc. and exposed to predation.
If this is a mechanism that sorts itself out in the early stages of year
class development, and you introduce an overpopulation of individuals to a
set amount of resources... You may weaken _all_ individuals to the point
where no one survives, because by the time you have a couple of the most
successful individuals in this interaction... They've spent up that ability
just trying to outcompete their own kind.
I don't know if anyone has studied this... But I would hope this is
considered when doing reintroductions. Especially since, in this case,
whatever resource that separated them from other species obviously wasn't
proliferant enough to maintain them when they diminished.
I can see this as _critical_ in say, madtom reintroductions, which may be a
I mean, really, why don't madtoms rule the earth? It's hard to eat them
because they sting like hades... There's plenty of well aerated riffles in
North America now without point source pollution to kill them... With all
these mayflies and stoneflies coming back, there's plenty of food... Second
year class should be gobbling up young darters a plenty making room for
other catfish that eat the same food as the darters... They have a cryptic
lifestyle that lets them eat when no one else is, and live in habitat that
is impossible for sizely predators to get into...
Why do we only see a few when we sample even the most high quality madtom
... and that is the thought for today :)
The Muddy Maumee Madness, Toledo, OH
It's never too late to have a happy childhood.
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: Fri Dec 31 2004 - 11:27:43 CST