Re: NANFA-L-- A Deluge of Snakeheads

Bob Bock (bockhouse at earthlink.net)
Thu, 13 Oct 2005 11:59:53 -0400 (GMT-04:00)

Well, I hope I'm wrong. And Lake Victoria might be a more apt analogy, although that wouldn't apply exactly either. When I seined the Crofton Pond, I worked the lilly pads for several hundred yards along the shore line. I netted 2 bluespots and a baby bluegill. It was really weird to see that much shoreline with so few small fish in hiding. Snakeheads are far better at parental care than the centrarchids, and probably, any other top of the line predator in the Potomac system. Moreover, they appear to grow at a faster rate than do most other predatory fish in the system. (An angler landed a Crofton snakehead that was bigger than a golf bag. At that point, the snakeheads had only been in the pond for less than two years.)

Because of their greater early survivability and (presumably) faster growth rate, one could see the snakeheads rapidly becoming more numerous than other top of the line predators, severely stressing the available forage, perhaps driving many local forage species into extinction. It's possible that only the largest of bass, catfish, and carp could survive the onslaught.

Anyway, I hope I'm wrong.

-----Original Message-----
From: "Todd D. Crail" <tcrail at UTNet.UToledo.Edu>
Sent: Oct 12, 2005 7:28 AM
To: nanfa-l at nanfa.org
Subject: Re: NANFA-L-- A Deluge of Snakeheads

----- Original Message -----
From: "Bob Bock" <bockhouse at earthlink.net>
> It wouldn't surprise me if the snakeheads took down the bass population.
Considering that they've only been in the Potomac system for two years, they
appear to have reproduced at a phenomenal rate. This looks like it's really
going to be a disaster. Like Boiga irregularis and Guam.

Not necessarily. You have two completely different scenarios there for the
invasion, with Guam (or Hawaii, or the Galapagos, or Carribean islands, etc)
being FAR more sensitive to a new predator in the network explicitly because
of the island biogeography. What would happen in Guam if a colony of
predators floated in on some drift from a typhoon? The same thing may
happen, just not in the scale of our lifetimes. The insane bird
biodiversity may ONLY be because no predator has appeared on the island,
prior to our noticing there were a lot of different birds there, no?

Conversely, these things are arriving on far faster scale than geologic time
(within our lifetimes). So, I'm not saying this is a good thing for
humanity's sake, since we're only really a burp in that geologic time as
well.

My guess is... The snakeheads are filling an empty or vaccant niche, which
recruitment from each brood is exceptionally high, and why it appears
they're populating at an incredible rate. The invasion front is going to
look like the things are crawling out of every crack and crevice in systems
that have this empty or vaccant niche, we _may_ observe a bottleneck in
native predators, but probably when it's all done and said, there's not
going to be much of a difference except that other predators will have less
food than before the introduction, and the possibility that a couple species
will experience loss due to heavy predation because they happen to cross
food networks with the snakehead or try and nest in the same area which gets
interrupted.

Yes, this falls apart when considering nile perch. But that's nile perch...
;)

Be FAR more concerned about those wiley asiatic carps that are loose in the
Mississippi. They may have a less charasmatic demeanor to their villainry.
But they interrupt the food networks where everyone above needs to feed, and
that... That's a problem.

Todd
The Muddy Maumee Madness, Toledo, OH
It's never too late to have a happy childhood.
http://www.farmertodd.com
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