Moontanman@aol.com wrote:
_Click here: Non-Native Fish May Be A Benefit Not A Burden_
(http://www.scienceda...80226171618.htm)


Don't shoot the messenger I just thought every one should be aware of this.

Michael

I've changed my mind! Fire away! I think most everyone knows that I am not exactly on the side of no releases if they are for the right reasons. Most damaging releases of exotics are done by and promoted by the government for the benefit of sportsmen, then you have escapees from food aquaculture, escapees from aquarium aquaculture, and bringing up the rear are intentional releases by people who either don't care or don't know better.
I would not be opposed to releasing a fish that has either lost or is losing it's native habitat for what ever reason. A lot more thought and study would have to go into it than "wow lets release peacock bass and get more fishermen!" If any of you have forgotten or maybe you weren't around when I advocated the establishment of endangered sturgeon in certain rivers or other fish that have been fished out or lost their native habitat. Does Pseudoscaphirhynchus kaufmanni, Pseudoscaphirhynchus hermanni, Psephurus gladius , or maybe the Yangtze river dolphin ring a bell? We could have possibly saved these species from extinction but we would rather introduce fish that it was known before hand they would cause problems. Personally I would rather cause a problem trying to save an endangered species than causing a problem to make sport fishing better! We are going to introduce exotic fish, we have done so and will do so again and again. It's simply what humans do, we introduce non native animals outside their native habitat! Why not take a provocative proactive step and try to do good instead of just pleasing a select few at the expense of the many? Yes introduced fish are a problem, but were any of the problem fish really a surprise? I mean if you introduced Surilus glanus into the Mississippi river system could you say "Well I didn't think they would be a problem?" North America has diverse but disparate fish population. By the time all the ecological niches are filled by Native North American fish North America will have collided with another continent and get a huge number of competitors naturally, that is if humans don't keep on until there is nothing left but bass, trout, and carp!


Michael Hissom
aurea mediocritas

I dunno, there's a long history of people releasing exotic animals thinking they're doing everyone a favor even if it's not for sport purposes. The person who released starlings in Central Park in Manhattan in the 1880s thought he was doing the US a favor by introducing a bird that appears in Shakespeare's plays; what could go wrong?

I dunno, there's a long history of people releasing exotic animals thinking they're doing everyone a favor even if it's not for sport purposes. The person who released starlings in Central Park in Manhattan in the 1880s thought he was doing the US a favor by introducing a bird that appears in Shakespeare's plays; what could go wrong?

And oddly enough they're loosing ground in their native Europe.

I dunno, there's a long history of people releasing exotic animals thinking they're doing everyone a favor even if it's not for sport purposes. The person who released starlings in Central Park in Manhattan in the 1880s thought he was doing the US a favor by introducing a bird that appears in Shakespeare's plays; what could go wrong?

Starlings were destined for North America anyway. Cowlings of aircraft, wheel bays, (landing gears) these pests get every where and they do make their way here on airplanes. Just they fly for free. Just like the House finch often confused with the Purple finch. Brought here in the past as cage birds from the west. Became Illeagle to sell, people freaked and released them all, and now the ranges of the Purple finch and House finch overlap from east to west.

This is not a fishy topic but I am an avid bird watcher also so I just threw in my penny.

The bigger story with both house finches and starlings is that the original ecological relationships between birds and the rest of the biota had been shredded by the end of the 19th century with the clearing of forests and destruction of prairies and wetlands. Ecological niches were gaping open, with the disappearance of the carolina parakeets and passenger pigeons just to head the list. With fish, it's much the same, sad to say.

The bigger story with both house finches and starlings is that the original ecological relationships between birds and the rest of the biota had been shredded by the end of the 19th century with the clearing of forests and destruction of prairies and wetlands. Ecological niches were gaping open, with the disappearance of the carolina parakeets and passenger pigeons just to head the list. With fish, it's much the same, sad to say.

Yep would love to go out and see some Carolina Parakeets today. And the passenger pigeon I read an article about one time that when a flock of them would fly over your head it would be so thick it would block the sun. Then the hunters would open fire and in no time they were gone. Wish we could learn from out mistakes but it just seems to go on. I am very happy to see some programs like Operation Migration with the Whoopers take place. I actually had one of my photos on their blog site a couple of years ago. The Hiwasee wildlife refuge is one of their stops and I was there. What an awesome site to see the whoopers follow the ultralights. I can dig up the photos I have and share sometime. Not fish I know but what the heck we are nature lovers right.

Daniel

Daniel-

If you can dig up John James Audubon's account of a passenger pigeon flock migrating overhead, it's a great read. However, the primary culprit in that species' extinction was not the unrestrained market hunting but the disruption of the vast unbroken forests they needed for nesting; as soon as loggers started opening up the forests of the upper midwest, the pigeons started declining. Which goes back to the point made earlier: habitat quality is the single most important factor in the success or decline of both indigenous and introduced species. Most 'weed' species, both plant and animal, take advantage of disturbed environments and vacated niches to establish themselves in new regions.

You can see this anthropogenic effect in the enormous range expansions of some animals in the last century or so: I can walk around my neighborhood and find coyotes from western North America, nine-banded armadillos from Mexico, and cattle egrets from Africa. None of these species were transplanted by man; they simply took advantage of the new habitat types we created in eastern North America, and in the coyote's case the extirpation of the red and gray wolves that would have been its major competitors in the past.

This is not to say that the introduction of exotics is harmless; that is clearly untrue in many cases, and in cases where effects are unknown, it's better to err on the side of caution. But maintaining habitat should be the biggest priority.

Daniel-

If you can dig up John James Audubon's account of a passenger pigeon flock migrating overhead, it's a great read. However, the primary culprit in that species' extinction was not the unrestrained market hunting but the disruption of the vast unbroken forests they needed for nesting; as soon as loggers started opening up the forests of the upper midwest, the pigeons started declining. Which goes back to the point made earlier: habitat quality is the single most important factor in the success or decline of both indigenous and introduced species. Most 'weed' species, both plant and animal, take advantage of disturbed environments and vacated niches to establish themselves in new regions.

You can see this anthropogenic effect in the enormous range expansions of some animals in the last century or so: I can walk around my neighborhood and find coyotes from western North America, nine-banded armadillos from Mexico, and cattle egrets from Africa. None of these species were transplanted by man; they simply took advantage of the new habitat types we created in eastern North America, and in the coyote's case the extirpation of the red and gray wolves that would have been its major competitors in the past.

This is not to say that the introduction of exotics is harmless; that is clearly untrue in many cases, and in cases where effects are unknown, it's better to err on the side of caution. But maintaining habitat should be the biggest priority.

I believe that is the article I speak of when I say I read about them. This was at Point Pelee Ontario. I assume you are familiar with this spot. Great for birding around mothers day when it is prime time for warblers migrating over the lake and that is their first stop. I have personally seen two hundred species there in a weekend. Used to live up there and make the trip once a year. Miss it but we are going to king ranch this month and down to Brownsville Texas and then points up the Rio Grand and no people I am not bring fish back this is a birding trip with my wife and youngest son.

And thanks for the info here about James he was and is a real hero in the nature world.

I dunno, there's a long history of people releasing exotic animals thinking they're doing everyone a favor even if it's not for sport purposes. The person who released starlings in Central Park in Manhattan in the 1880s thought he was doing the US a favor by introducing a bird that appears in Shakespeare's plays; what could go wrong?

I didn't avocate individuals releasing something they liked or thought would be a good idea. Lots of study would have to done before any exotic was released. At the very least more study that the state seems to do.

Michael

Just to add another angle to an interesting thread;
I read somewhere a theory that I have since embraced which suggests the passenger pigeon was already doomed by the time market hunting started to take its toll.
Essentially, the emense flocks described from Audobon's time were a result of dire over population and represented a population level which could not sustain itself. Think about it; many of the accounts describe the flocks stripping every last bit of food from an area as they passed through. Even trees and branches breaking under the weight of roosting pigeons.
This just doesn't sound like a natural, healthy, sustainable population level.
Also, older accounts do not contain as many accounts of such high population levels.
It was suggested that Native American land use changes with the introduction and growth of agriculture had allowed the pigeons to expand and over populate. By the time of the market hunters, the pigeons were well on their way to deccimation by famine and disease. In fact, these forces may already have been in play and the market hunters just tipped the balance and sealed the deal.
Interestingly, the author suggested the same scenario for bison.

Just to add another angle to an interesting thread;
I read somewhere a theory that I have since embraced which suggests the passenger pigeon was already doomed by the time market hunting started to take its toll.
Essentially, the emense flocks described from Audobon's time were a result of dire over population and represented a population level which could not sustain itself. Think about it; many of the accounts describe the flocks stripping every last bit of food from an area as they passed through. Even trees and branches breaking under the weight of roosting pigeons.
This just doesn't sound like a natural, healthy, sustainable population level.
Also, older accounts do not contain as many accounts of such high population levels.
It was suggested that Native American land use changes with the introduction and growth of agriculture had allowed the pigeons to expand and over populate. By the time of the market hunters, the pigeons were well on their way to deccimation by famine and disease. In fact, these forces may already have been in play and the market hunters just tipped the balance and sealed the deal.
Interestingly, the author suggested the same scenario for bison.

Unfortunately (well, more like fortunately), that's not how population dynamics works. As a background, the number of individuals of a species that an environment can support is called it's "carrying capacity". If a population is well below its carrying capacity, then it will shoot right up, with high birth and survival rates. It will result in a population size that is above carrying capacity. Then, the population declines to below carrying capacity, but isn't wiped out entirely. It will then go up again, and down again, etc. If the carrying capacity stays the same, it will eventually level out. Basically, even if there are way more individuals than can be supported, as they die, the others get the resources until enough have died that there are more than enough resources to go around, thus raising the population again.

Now, this is complicated by the fact that carrying capacity is not a static number - it is always changing as the total amount of resources in the environment changes (due to predation, etc.). Plus, the life history of an organism has an effect - if it breeds constantly, the above model fits very well. If it breeds only once per year, then the fluctuations are greater. If it breeds, say, every 17 years, then yes, it is possible for it to be extirpated in a given location.

The idea you found is right that a species can be decimated by disease. But not by a famine due simply to overpopulation. This would only work if the famine were caused by other factors, such as habitat/food loss, which would lower the carrying capacity to a very low number. In that case, there would be few individuals and the randomness of finding food and mates and being eaten could certainly wipe them out.

The original article that prompted the Science Daily coverage was in Fish and Fisheries. That volume is open access for the moment, so anyone can download the article as a pdf:

http://www.blackwell...com/toc/faf/9/1

I'm not very comfortable in the approach that the author used: a meta-analysis of FishBase and an FAO database (neither of which are particularly thorough for non-taxonomic information), followed by a literature review for impacts -- particularly when they provides neither the exact list of species used nor the list of references used to characterize negative impacts. I sent the author a polite email asking for his data set (which should have been included as an appendix in the paper), and got a response essentially telling me that I should go recompile it on my own... Ahh, the sprit of comraderie among scientists. Anyway, without the list of publications that the author used, there's no way to independently assess whether the author really thoroughly reviewed the literature or if, say, the 52% of species introduced outside of their native range that he reported to have no impacts were in areas where few people are working on fish ecology (most of Asia, much of Africa, etc).

Anyway, you should still read the paper, if only to see what the fuss is about.

In areas where we have data (like western Europe, and North America), the case is clear -- if an introduced fish species becomes established, it's going to have some negative impact on some portion of the native biota, even if the native fauna has already been highly modified or disturbed. Even species that become established but don't seem to be ultra-invasive at the moment (in North America, tubenose gobies and tench come to mind) are still displacing or affecting behavior of native species (not just fishes) or causing shifts in prey abundance or densities just by being there. Impacts may be subtle, but unless these species are being established in a vacuum, they're still going to be present.

Moon, if we were really serious about saving things like Pseudoscaphirhynchus (rather than using captive propagation and translocations as a lame excuse to get some for aquaria), we should be trying to provide alternatives to cotton farming in the Aral Sea basin, incentives to switch, and reducing irrigation withdrawals from the inflowing rivers. Oh wait, that might actually improve the quality of life for folks in the region -- the State Department would never go for that...

cheers,
Dave

Unfortunately (well, more like fortunately), that's not how population dynamics works. As a background, the number of individuals of a species that an environment can support is called it's "carrying capacity". If a population is well below its carrying capacity, then it will shoot right up, with high birth and survival rates. It will result in a population size that is above carrying capacity. Then, the population declines to below carrying capacity, but isn't wiped out entirely. It will then go up again, and down again, etc. If the carrying capacity stays the same, it will eventually level out. Basically, even if there are way more individuals than can be supported, as they die, the others get the resources until enough have died that there are more than enough resources to go around, thus raising the population again.

Now, this is complicated by the fact that carrying capacity is not a static number - it is always changing as the total amount of resources in the environment changes (due to predation, etc.). Plus, the life history of an organism has an effect - if it breeds constantly, the above model fits very well. If it breeds only once per year, then the fluctuations are greater. If it breeds, say, every 17 years, then yes, it is possible for it to be extirpated in a given location.

The idea you found is right that a species can be decimated by disease. But not by a famine due simply to overpopulation. This would only work if the famine were caused by other factors, such as habitat/food loss, which would lower the carrying capacity to a very low number. In that case, there would be few individuals and the randomness of finding food and mates and being eaten could certainly wipe them out.

You'll have to excuse my ignorence, I'm just an uneducated layman and not qualified to expand on such complicated issues.
However, that's never stopped me before so here goes;
Population dynamics is essentially a 200 year old mathmatical formula. Although it useful to government fish and wildlife agencies for producing funding, justifying policy decisions and keeping the media and public quiet, it is not very useful for describing the natural world.
The problem lies in that it is a function of mathmatics. Math does not mesh well with natural systems because math is absolute. Two plus two ALWAYS equals four and no amount of meddling by man or nature can ever change that.
In nature, two plus two only equals four until a prolonged drought wipes out a primary food supply or until humans wipe out a primary preditor or until an introduced invasive species changes the ecological balance or until all of these things plus more happen at the same time.
At the time of the passenger pigeon's demise, the ecosystem of eastern North America was in a state of unprecidented flux.
First the natives had drastically altered the enviroment with agriculture and associated population increase. Following immediately after, Europeans came on the scene with their even more drastic agriculture practices, gigantic population increases, industrialization, unregulated harvest, introduced species and diseases.
So many drastic changes in such a [geologically] short time frame was too much for some species to adapt. As Dave said [taken somewhat out of context], "Impacts may be subtle, but unless these species are being established in a vacuum, they're still going to be present." And we ain't talkin subtle impacts here!
Having said all that, if you were to strike my use of the word "famine" from the account above, it would still be a viable theory and worthy of being given some thought.

Many of the southeastern U.S. Indian populations were hugely reduced by introduced European diseases in the 1500s, often by as much as 90%. By the time that English-speaking Americans encountered the Cherokees, Creeks and others in the 1600s, their populations were still not nearly recovered to pre-Columbus times. If the passenger pigeons were dependent on these Indians' agricultural output, and altered environment, I suspect the pigeons would have been in trouble as of 1700 rather than requiring the market hunting of the mid-1800s to exterminate them. Many populations in nature go through large oscillations, so the fact that passenger pigeons would show up in areas and consume everything edible doesn't inherently means it's "unhealthy"; merely, it means that it can't happen every year, and the pigeons would have to move on, which is what they were famous for (hence the name "passenger").

Unfortunately, introduced fishes don't have such behaviors, although I guess you could make an argument that exotic starlings have the same opportunistic resource use patterns. Luckily I don't have any starlings roosting near my house this year...

It's ironic that the news journal that the piece in question was published in had this article linked on the same page. "Mass Extinction Of Freshwater Species In North America"
http://www.scienceda...90930072250.htm
Containing this passage;
"One major threat to freshwater animals is non-native species. For instance, zebra mussels introduced from Europe are outcompeting native mussels in lakes and rivers."

Although the author suggests there are "... measurable benefits to be gained to the ecology and economy by the appropriate introduction of non-native species." I think his reasoning is slanted more toward the "economy" than the "ecology". For purely human benifits, a good argument could be made for introducing certain species.
No one will dispute the billions of dollars sportfishing [for mostly introduced species] has generated.
I guess the nile perch might provide more calories to the native diet than all those endemic cichlids it displaced.
Some arguement might even be made for a "lesser of two evils" point of view. Is the ecology better served by the introduction of gambusia vs DDT for malaria control? Again, with the emphasis on human benifits. If anything, malaria may have protected certain ecosystems by excluding humans. Look at what has happened to Africa since the tropical regions have been opened to human colonization with malaria eradication.

Many of the southeastern U.S. Indian populations were hugely reduced by introduced European diseases in the 1500s, often by as much as 90%. By the time that English-speaking Americans encountered the Cherokees, Creeks and others in the 1600s, their populations were still not nearly recovered to pre-Columbus times. If the passenger pigeons were dependent on these Indians' agricultural output, and altered environment, I suspect the pigeons would have been in trouble as of 1700 rather than requiring the market hunting of the mid-1800s to exterminate them. Many populations in nature go through large oscillations, so the fact that passenger pigeons would show up in areas and consume everything edible doesn't inherently means it's "unhealthy"; merely, it means that it can't happen every year, and the pigeons would have to move on, which is what they were famous for (hence the name "passenger").

Unfortunately, introduced fishes don't have such behaviors, although I guess you could make an argument that exotic starlings have the same opportunistic resource use patterns. Luckily I don't have any starlings roosting near my house this year...

I don't believe the theory was that the pigeons were "dependent on these Indians' agricultural output" so much as they had benifited from changes in land usage, particularly the patchwork clearing of thick forest.
I should add that the theory I'm describing came from an archaeologist [name escapes me] who's specialty was prehistoric agriculture and not a biologist. I still think it has merit, probably because I read the whole book and not just the snippits I give here.

Chris, I assume you're working on a reply to the Nile Perch comment?

Chris, I assume you're working on a reply to the Nile Perch comment?

If you mean my nile perch comment, I hope you noted the qualifiers "I guess" and "might provide" and also the topic heading "Devil's Advocate"!
I have no love for nile perch. African cichlids occupy a special place in my fish lover's heart and anybody who drove any african cichlids to extinction before I got to at least see pictures of them is bad in my book.
I will admit I'd like to get a nile perch on my nine weight. Maybe when I visit Texas.

I guess he wasn't working on that!

Sure, there may be a short-term economic incentive to introduce exotic stuff, but when you discover that your wonderful new introduced sportfishery has fundamentally changed the trophic dynamics of say, Lake Michigan by knocking down populations of zooplankton-feeding pelagics, and that the shift in zooplankton community results in a reduction in algal grazing, and all the sudden you wind up with additional crud that you have to filter out of your municipal/industrial water supply ($), with mats of crud washing up on beaches (and less tourism $$), and algal-associated reductions in DO that kill off your precious introduced predators (more $)... Estimates of sportfishing dollars for exotic species fail to take these kinds of costs into account. I think economists may be the second most short-sighted people on the planet, coming in close behind politicians.

Ecology 101: if you replace a suite of mid-trophic level specialists with a top predator at a higher trophic level, you won't get the same amount of biomass - the laws of thermodynamics make it impossible! You'll almost always wind up with much less than what you started with.

You want to talk about Nile Perch? Yeah, so they're big (and yes, they would be fun to flyfish for -- in their NATIVE habitat!). The total amount of food that's available for local people is less than prior to the introduction. The fish require more processing to preserve (you can't just sun-dry them like you could mbuna), more expensive equipment to catch, and the shift from a traditional fishery to an industrial fishery has had massive socioeconomic impacts. Much of the catch is processed and shipped out of country -- too expensive for locals. The loss of snail-feeding smaller cichlids, introductions of water hyacinth, algal blooms and reductions in water quality have led to increased rates of schistosomiasis and bilharzia. Check into it -- it's not a good example to follow.

Dave

I had forgotten the schistosomiasis connection but I had read that somewhere. Probably in an account of collecting cichlids for the trade. Crocodiles, political unrest and schisto - am I sick for thinking those downsides ain't that bad for a dream job?

I don't disagree with any of the examples you gave, or the numerous others available.
Keeping within the context of the Devil's Advocate theme of the thread, and for the sake of arguement [another hobby of mine], it might be argued that some of the introductions throughout the ages have been less harmful. It could certainly be argued that the economic benifits have been greater than you have implied. The sheer magnitude of the largemouth bass fishing phenomenon comes to mind. Multi-millions of dollars annually is not at all unreasonable.
If we in the northeast were forced to rely only on native species to support our freshwater sportfishing efforts, well, there really wouldn't BE any sportfishing. I'm sure there have been detrimental effects. Most likely some of our more fragile minnows and inverts have suffered. OTOH, would any of those species be any better off given the degredation of their habitat?
How do you attach a value to a small minnow or crayfish so that you can balance it against the value added to the economy? [Devil's Advocate! Devil's Advocate!]
If sportsfishing wrankles for it's frivolous nature, what about more altruistic endeavors? Gambusia for malaria control or tilapia for famine relief? Assuming either of these efforts ever reaped significant reward, would it be fair to say the value gained offset the value lost in the form of a few small organisms? [Devil's Advocate! Devil's Advocate!]
I guess the question is, how do we define "Value"?

Edited by mikez, 05 March 2008 - 04:55 PM.