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Re: Dealing with the real fish? problem
On Thu, 25 Jun 1998, mcclurg luke e wrote:
> Point of contention: no fish or animal is truly "native".
You can define it anyway you like, but I defined it in my previous
post, you are twisting my definition. _Most_ people agree that something
moved by modern man is not native. Things moved by natural causes are native.
One can argue that humans are natural too and that that makes translocations
natural. I don't agree with that definition.
> Populations rise and fall shift and change.
Sure.
> A fish is only native because man has documented it in that location.
We can only go on what we record. If we base things on unrecorded events we
achieve nothing. Do you have a better suggestion? If species are sufficently
studied populations can usually be shown to vary genetically, hence additional
new populations found can frequently be determined to be "native" or likely
introduced based on unique genetic info.
> What if we found a body of water after a
> earthquake which allowed two watersheds to intermingle where before they
> were separate?
Then it is native. If a human carries it in a bucket between the same
watersheds it is not native _by my definition_.
> It DOES happen. My point here is that while it is
> reasonable to say a South American Cichlid will not naturally invade the
> Great Lakes. It is also NOT reasonable to say that a fish found in one
> watershed cannnot colonize another...see below.
I _never_ said it cannot. I work on biogeography, I am well aware of how
natural events can shift fish around.
> Very true. But would you agree that if you are keeping fish from a
> specifici location and watershed that the diseases in your tank is the
> disease that came from that same location? Exotic diseases are a problem
> I understand that...don't get me wrong. I'm stressing the need to not
> OVER-react to disease threats. Simple common sense will normally win the
> day.
What about the fish in the other tanks you have that aren't from that area?
Do you ever use the same net in both tanks? Do you ever use the same syphon
hose in both tanks? Do you ever thoroughly wash your hands between sticking
them in seperate tanks?
It's not a matter of over reacting. It is a matter of being responsible and
making folks realise the risks posed. Sure, the chances are not that great.
But lets say 1 in 1000 times something negative happened. How many releases
occur in the USA a year? I have no clue, but I'll bet you it's in the
thousands. How many diseases are we prepared to risk introducing? The chance
is not that great but prevention is not that difficult or expensive either.
> Kansas biology especially, I know the conditions of these watersheds
> better than many outside the state. In short, they suck!
So because the watersheds are in bad condition we shouldn't worry about it?
> The fish I
> transport are not from the Arkansas drainage to the Kansas drainage.
> (perhaps I wasn't clear on that) They are from the Kansas drainage to
> farm ponds whose run-off goes back INTO the Kansas drainage.
The Arkensas drainage is huge! The Kansas is also not small. They are
certainly bigger than the Gila drainage out here. You are ignoring potential
microgeographic variation. In the Gila basin no two loach minnow or spikedace
populations are completely alike. Yet, they only occur in one drainage. The
whole idea is to be cautious. We don't know everything about the biology of
these species and we probably never will. It is nieve to think two
populations are alike just because they look the same to the naked eye. There
are far more potential subtle differences that could be important that the
naked eye cannot detect.
> Sport fishes
> are raised by Wildlife and Parks officials in hatcheries around the state
> from BOTH drainages and stocked in BOTH drainages. Whatever "killer
> diseases" might have been lurking out there have LONG since been
> intermingled.
That assumes more are not being added via aquarium releases. And also, just
because the state does it doesn't make it right and it doesn't justify anyone
else doing it.
> NO the threat in this state is not from fish moved between
> drainages...again see below for more...but from pesticides, feed lots, and
> urban sprawl sucking the very life out of our rivers. Fishes in this area
> tolerate disease much better than they do the other things.
They are all threats. I've never said translocation is the only threat, nor
the most important, just that it is a problem.
> With all due respect...whose principles? I don't mean to be insulting,
> but again, a muddy Kansas stream is far different than an Arizona spring.
> I see both of our philosophies have strong points, but they also have
> flaws. I think reasoning and WISE compromise solves more in the end than
> a one person, or one blanket approach to the issues.
Basic biological principles. Genetics, behaviour, ecology, evolution. You
can put two populations in different places, even if they are identical and
they may gradually change and likely in different ways to each other.
Species is a human concept that does not apply well to the natural world as
things don't "fit" into boxes. All this means is there is a difference
between what we see as a species and what "biology" (meaning things in the
natural world) see as species.
> It happens all the time here. We have a wonderful bird called the Great
> Blue Heron that doesn't recognize boundaries OR watersheds. They have
> "stocked" fish in waters that had none before. In our own family farm
> pond we had Green Sunfish AND Pumpkinseeds appear without any human help.
> NO, someone did not place them there, some BIRD did. I have personally
> witnessed Herons open their mouths to take a fish only to have several
> small ones drop into the water its fishing.
I don't agree with your observations above. Just 'cause you saw a heron drop
fish when it was fishing for others doesn't mean anything concrete. How do
you know it didn't just catch them and it only had them in it's mouth for a
very short period of time. How long is a heron likely to carry a live fish
around before eating it? I doubt it would be that incredibly far. Also,
these type of habitats _usually_ occur at lower elevations within drainages.
Hence, a bird is more likely to go to the next likely waterhole in the same
valley. Why fly over a mountain, carrying water and fish when the next
nearest fish population is likely not that far away in the same valley? Sure,
that will not _always_ be the case, but in most cases it will be. Surely too
once it is in it's gut it is dead right. How do you know the next farm
upstream of your pond doesn't have sunfish in their pond, or the farm above
them? Fish are amazing creature, you'd be surprised where they can get to
during extreme rainfall events. You don't need to have a significant
watercouse for them to migrate.
Also, no one, ever, has demonstrated that a bird successfully transported
fish, let alone one that started a new population.
Furthermore, I'd refer you to Cross, Mayden, and Stewart, Fishes in the
western Mississippi Basin. In, Zoogeography of North American Freshwater
Fishes. pp 363-411. In this paper they look at faunal similarity amongst
many drainages including the Arkansas and Kansas Rivers. They have a table on
page 398 showing the % faunal similarity between rivers in their study area.
The Kansas and various parts of the Arkansas have between 53-65% similiarity.
Within the Arkansas drainage the lower river and middle river are similar by
80%, the middle and the upper are similar by 74%. If birds shifted fish with
any degree of regularity wouldn't you predict that the levels of faunal
similarity would be higher--expecially between the two major drainages? Sure,
many of these will be habitat specialists, however, there are many native
species that are not shared by both drainages--especially cyprinids which are
typically mid water species making them more vulnerable to birds like herons
presumably.
> How do you suppose some of
> these species got so widely distributed in the first place?
They swim. Virtually all exceptionally widespread species are very tolerant
of a wide range of environmental conditions, ie they are very adaptable to
adverse conditions. Hence they are good survivors in a ranage of habitats
which makes them more likely to persist and spread.
> you suggest it... we do not live within miles of any creek that carries
> the two species and there are enough high obstacles (small waterfalls
> mainly) to prevent invasion. It's possible, but not the only possibility.
> Also, don't forget about snapping turtles, beavers, waterfowl, etc. who
> all don't recognize watershed boundaries but travel where and when they
> please. It's too easy to get panicked about introductions and disease.
> The point is, it happens regardless of man's participation.
But, do you agree that humans increase that risk? I'm not trying to create
panic, just awareness.
> Exotics verses introduced natives is a difficult discussion.
How do _you_ define exotic and introduced?
> I hope I haven't offended anyone.
Not me anyway. :-)
> In the same light, I tend to get a little punchy when someone
> from another part of the country starts telling me what I need to do in my
> own backyard, when I know darn well that person may not have all the
> information I have on the subject.
Likewise, I tend to get emotional when folks ignore principles that are mostly
independant of geography. :-)
I'm glad you've kept the questions and arguments coming.
Cheers
Peter Unmack
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