Jeff Fullerton has some thoughts on this, which he asked me to forward (he's
still having problems with outgoing mail messages to this list):
-----Original Message-----
From: Jeffrey Fullerton
Sent: Wednesday, December 15, 1999 12:28 AM
I would like to add my two cents about outdoor ponds: When I first started
out I built an earthen dam in a small spring flow that crosses the property.
I was a kid then and those were the days before anyone gave much thought
about the escape of exotic fishes and disease transmission to wild
populations. In the spring my setup was prone to flooding and I often lost
fish. Fortunately I only had access to fish stocks from Greenlick and a few
other local drainages - so whatever
escaped was in most cases returning to the same system that it came out of.
Of course over time I got tired of loosing fish , so I moved my operations
to higher ground and diverted water from the spring via a plastic pipe to
fill the ponds as needed. I learned that keeping the pond as a closed system
cuts down on algae bloom since continued inflow brings fresh minerals that
feed algae, as well as siltation and risk of flooding. This change of method
was more a result of enlightened self interest, but in time I learned also
that as a pond keeper that I should take the responsibility to prevent
escape of my fish to the local drainage as well as resisting the temptation
to release surplus specimens into local waters. I must confess there was
once a time that I would have thought nothing of introducing Eastern
Mudminnows to a slough down the road or planting water lilies in the nearby
lake.
But even before I had joined NANFA a few years ago, I learned that would not
be a good thing to do.
As for ecologically responsible pond keeping , I can suggest a few
guidelines and invite others to contribute as well. If you are keeping fish
outdoors, they should be contained so they will
not escape into local waters. A pond should be maintained as a closed
system - that means the water should be filtered and recirculated as opposed
to a continuouis flow that drains into the local watershed. Since ponds do
overflow in periods of heavy rain, some kind of catchment - a screened
outlet that drains into a drywell (gravel filled soakage pit) is a good
idea. The idea is to strand any fish that might leave the pond and ensure
they die before they can make it to another body of water.
If you live on a floodplain or have an open system that continuously drains
into the watershed, then you should stock only fish stocks from that
watershed - ie dace or sunfish from Greenlick Creek being put into a pond
that drains back into Greenlick would probably be ok, but not something you
brought home from Wisconsin or Virginia. The same also should apply to farm
ponds - although it often dosen't.
This raises the issue of how we might be able to talk to our state fish and
game people about the way local fish stocks are managed. If conserving the
genetic integrity of local populations of Bass or channel cats is important,
then shouldn't fish hatcheries be propagating fish from locally collected
stocks as opposed to importing them from another hatchery in a different
climate zone?
When it comes to outdoor ponds, there should be a list of species to avoid.
If the state in which you live does not have a list of prohibited species,
then the hobbyist should first of all avoid those species that have well
established reputations as noxious troublemakers - ie Red Shiners, Swamp
eels, walking catfish , etc. When keeping non-indigenous species - fishes
that are fussy about habitat and water chemistry, are more easily
contained - ie acid water species like Blackbanded Sunfishes do not compete
well against circumneutral fish populations. Southern species that are
marginally hardy in northern states , or tropical fishes being summered
outside are other examples. The life history and thermal tolerances and
fecundity of a given species defines whether it is potentially invasive or
benign and that varies with climate and local
water conditions. Gambusia and Fathead Minnows which are a holy terror in
the west are not much of a problem here in the east. Many tropical fish that
cannot survive in the north have the demonstrated potential to establish
themselves in the deep south, or in warm springs in the north.
The best way to avoid trouble is for hobbyists to educate themselves about
responsible fish keeping and to share that information among themslves. We
should all listen to one another and understand instead of bickering. There
comes a time to stand up for what you believe in, but
also a time to let it go and move on.
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