Snakehead ?

Ashtonmj, has the state of Maryland considered doing control measures on the SNakehead the way some Western states are doing them on Northern Pikeminnows (put small bounties on their capture)or maybe having a annual Snakehead tournament in the middle of their spawning season?

The US Fish and Wildlife, Maryland Fisheries Office, conducts surveys and implement control measures for snakeheads. The point of contact for the Service's efforts in MD is Mike_Mangold@fws.gov He could give you an accurate summary of their efforts.

"Report" videos of fish eating fish? Are you serious?

Moonbat. California.

Case closed

I believe the "Bullseye Snakehead" in Southern Fla was taken off the kill list. Studies show that the native fish can co-exist with the snakeheads.

I believe the "Bullseye Snakehead" in Southern Fla was taken off the kill list. Studies show that the native fish can co-exist with the snakeheads.

Huh? Please reference these studies of which you speak.

Oh, and ALL snakeheads are still covered under the Federal ban on import or interstate transport (the official ruling can be found here.

Have a nice day!

According to the FWC ALL Snakeheads are considered prohibited fish! Heres the link http://myfwc.com/WIL..._Prohibited.htm .

Edited by wargreen, 10 December 2010 - 04:42 PM.

"Report" videos of fish eating fish? Are you serious?

I'm speaking of the Illegal snakeheads people have in their tanks that post youtube videos laughing and playing gangster rap while the poor bass or sunfish of equal size is being torn apart slowly dying. Yes I am serious.

I'm speaking of the Illegal snakeheads people have in their tanks that post youtube videos laughing and playing gangster rap while the poor bass or sunfish of equal size is being torn apart slowly dying. Yes I am serious.

I've seen some of those videos, and I can understand why they'd upset you. If you feel protective of the fish being eaten, then they seem very cruel, very cruel indeed.

A suggestion: snakeheads are supposedly very tasty. Perhaps one of the control efforts could be to spread word of how tasty and delicious they are.

Studies show that the native fish can co-exist with the snakeheads.

There's a published study based on multiple years of systematic sampling in S. Florida canals, I think done by FWC biologists, that didn't find any definitive damage (yet?) from the presence of the (FWC-) introduced peacock bass.

Snakehead = very different.

Here is an article from 2006 talking about the Potomac.
http://news.national...snakeheads.html

But so far the snakeheads appear to have had little discernable impact on the native ecosystem, to the relief of scientists and anglers alike.

"We have not seen any adverse effects," said fisheries biologist Steve Owens, with Virginia's Department of Game and Inland Fisheries in Fredericksburg.

I'm not sure how credible that source is. We would have to contact this Steve Owens person and ask him if he still has that opinion now in 2011 and what data he based that statement on.

Edited by EricaWieser, 14 April 2011 - 01:57 AM.

I do not know how they got there but this study indicates that each areas of introduction were different haplotypes, meaning they were entirely separate introductions involving different instances of introductions.
http://www.bioone.or...TNSCAA]2.0.CO;2

It is true that invasive destruction is often overhyped and presumptive, but when it is bad it is indeed bad. It is always a role of the dice. Yet if the cost of natives was calced the way it often is for invasives some of them would look worse. This is in no way a defense of introducing invasives, for reasons too numerous to go through. Do not do it!

Nat Geo is outrageously awful on anything to do with science. It makes no difference which branch of science or logic either, though the gross negligence is more apparent when they deal with a subject you actually know something about. Even their UFO show, which there is nothing wrong with in principle, selects hypotheses from long list of hypotheses in different branches of science, talks about them as if they are the only hypothesis, and then pretend that the lack of accident that they are related was something more than their own confirmation bias. They are also the ones behind the so called scientifically verified (faked) feathered dinosaur (dino-bird), which no scientist even knew about before NG tried to scoop the scientist, who then called them out on the fake almost immediately. Yet this same BS is still used by creationist to claim all such feathered dinosaurs are fakes. I would not trust NG to identify my piss if they were soaked in it.

That said about NG they might not be too far off in that article. The mechanisms in population dynamics can be controversial among ecologist, though trophic cascade is not. In the most productive ecosystems the biomass of the top predators tend to inverted or greater than the prey species. Here are a couple examples which shows this trend and example effects:

Baselines and Degradation of Coral Reefs in the Northern Line Islands

Positive Effects on game Species of Top Predators by Controlling Smaller Predator Populations: An Example with Lynx, Mongooses, and Rabbits

I can outline a general algorithmic explanation of this efficiency inversion with predators but gets too far off topic. Yet we have removed the top predators in many native ecosystems and our present conservation efforts makes the simplistic assumption that predator equals danger for the species we wish to protect. Hence the lack of ecological balances, by loss of top predators, is forcing nature into a new balance which we are trying to prevent through conservation. Meanwhile the very species we are protecting continues to suffer from these imbalances. Perhaps I need to do another thread on these balancing forces in ecology, though applying it to any particular mix of species is extraordinarily problematic. So releasing any given invasive species is a crap shoot, and way too chaotic at the rate we are producing these changes for nature to effectively reach an effective quasi-stable state.

Edited by mywan, 14 April 2011 - 04:29 AM.

It sounds like you're trying to define a doctoral research project.

No, it just seems obvious to me why healthy ecosystems are top heavy with predators, like an inverted pyramid. From a physics perspective life has the same role and function as tornadoes, to increase the efficiency of entropy in a system that is pumped by an external energy source (sun) so as to maintain some degree of lowered entropy indefinitely. The 3 or 4 level trophic cascades is a valid characteristic of selected variables but do not define the algorithm which created these ecological variables. Hence the criticism that trophic cascades are not ubiquitous is valid on several levels. Including variables in food chains that blur distinctions between trophic levels, biotic and abiotic variables, keystone species for reasons other than predation like nesting, etc. Trying to define trophic cascades as a driving force in ecology is a little like trying to define species as the driving force of evolution. In fact species is a consequence of evolution rather than a cause, just as trophic cascades are a consequence of ecology rather than a driving force of ecology. It certainly does not invalidate the reality of trophic cascades, they are just not as fundamental as they are often assumed to be.

it just seems obvious to me why healthy ecosystems are top heavy with predators, like an inverted pyramid.

Ecosystems top heavy in predators create an Hourglass not an inverted pyramid... A healthy ecosystem is a box.

See, "Trophic Structure and Productivity of a Windward Coral Reef Community on Eniwetok Atoll" by Howard T. Odum and Eugene P. Odum, 1955, an Ecological Monograph of the Ecological Society of America.

Ecosystems top heavy in predators create an Hourglass not an inverted pyramid... A healthy ecosystem is a box.

What's "unhealthy" about the hourglass, and where do you find an ecosystem so balanced that it would make a box? Perturbation isn't just something that humans invented

Todd

Edited by farmertodd, 14 April 2011 - 08:31 PM.

What's "unhealthy" about the hourglass, and where do you find an ecosystem so balanced that it would make a box? Perturbation isn't just something that humans invented

Todd

Not sure your reading me right...but that is fine as I do not expect that with cryptically sarcastic text that likely only the author gets.

I am not sure how a predator top heavy ecology could be conceived as an hourglass unless the predators at some trophic level were underutilizing the pray for some reason. Or is that a presumption of predator overutilization? The box graph assumption gives me the impression that each food chain level is strictly stratified with each level working at perfect efficiency. This box graph is perhaps related to a quote in the paper fundulus mentioned:
"Trophic Structure and Productivity of a Windward Coral Reef Community on Eniwetok Atoll" by Howard T. Odum and Eugene P. Odum, 1955, an Ecological Monograph of the Ecological Society of America.

It has long been felt that the productivity of the various trophic levels of a community is very roughly proportional to the standing crop being maintained although the reason has not been entirely clear.

Consider a highly simplified system for conceptual purposes. You have an autotroph such as an algae with a predator that feeds on it. The predator overgrazes the alga to the point they limit their own food supply and goes through starvation cycles. Only a very small percentage of the predator population is needed to maintain a healthy population level. Meanwhile, during the starvation cycles of the predators the algae is overgrazed. Hence the abiotic resources used by the algae go underutilized for lack algae to utilize it. Think of the massive nutrient load we are choking rivers and estuaries with, in which the major limiting factor is abiotic, i.e., the oxygen it depletes from the water.

Now if we add a second predator B that feeds on the first predators A what happens? Then B can feed on the majority of A without effecting the ability of A to maintain a healthy population. Also removing the least fit among A making what population remains healthier. Also reducing the overgrazing on the algae, reducing underutilization of abiotic resources consumed by algae, so that ideal population levels of predators A is greater with B than without. Now potentially B can over predate on A, resulting in underutilization of algae such that both A and B experience periods of suppressed population levels. A third predator of B would stabilize it even further. In some cases to some degree the same effect can even be provided by predation of the young of the same species.

This overly simplified food web optimizes biomass production but does not explain the top heavy distribution predators in living biomass. Consider the bottom producers, algae in this case. Algae reproduces some number of times and eventually dies. But with predators present some chance exist that it ptoduces some number of times and is then eaten. So what would have otherwise been dead biomass is now swimming around looking for its next meal. This continues up through all trophic levels, where even those that die of old age becomes food for predators on their carcass. Hence the increase of biomass among the top predators is not the result of removing that biomass from their prey (where I presume the hourglass comes from), but by increasing the total volume of biomass that remains living at any given time. You also have different lifespans, metabolic rates, etc., to contend with. Consider our own consumption rates if we required the same consumption relative to body mass as a shrew. The body mass of a predator is often determined more by successful survival than it is consumption rate.

The model described is massively oversimplified. Intended only to illustrate that the biomass available to living organisms is not limited by the biomass of available prey. The available biomass actually grows continually as a product of autotrophs which in turn depend on predators. Most fundamentally in the carbon cycle but in many other ways as well. The feedback between trophic cascades and resource limits increases the overall efficiency regardless of the efficiency of any one variable.

With respect to snakeheads and introduced species we simply do not know in any given instance what species we are relieving pressure on or adding pressure to. Due to the effects described just because a snakehead predates on a given species does not mean any overall survival pressure has increased on that species, perhaps even reduced. Likewise, the fact that a species is not being predated on is no indication that their survival pressure is not increased or decreased. It is a crap shoot. We simply do not know. It does not take pushing a species over the edge for these survival pressures to incrementally increase or decrease either directly or indirectly.

Not sure your reading me right...but that is fine as I do not expect that with cryptically sarcastic text that likely only the author gets.

Yep, that flew right over my head

Todd

Here are the facts the VGIF and other state biologists are getting from population surveys from electroshocking and netting. "Although the VDGIF staff has done less
electro-shock sampling this year than
previously, their catch has gone up
exponentially, more than doubling the
number captured in 2004-2005 combined.
“There has been a big increase in the
Occoquan River system,” Odenkirk said,
and they have been found far upstream.
Larger numbers of fish have been found at
Belle Haven and in Pohick Bay. Substantial
increases have been observed in Oxon
Creek on the Maryland side, as well as in
Mattawoman Creek."
Other studies show that the Snakeheads biomass is indeed increasing in the Potomac and that theyre favorite food is Sunfish and topminnows.

Edited by wargreen, 15 April 2011 - 12:06 PM.

Here are the facts the VGIF and other state biologists are getting from population surveys from electroshocking and netting. "Although the VDGIF staff has done less
electro-shock sampling this year than
previously, their catch has gone up
exponentially, more than doubling the
number captured in 2004-2005 combined.
“There has been a big increase in the
Occoquan River system,” Odenkirk said,
and they have been found far upstream.
Larger numbers of fish have been found at
Belle Haven and in Pohick Bay. Substantial
increases have been observed in Oxon
Creek on the Maryland side, as well as in
Mattawoman Creek."
Other studies show that the Snakeheads biomass is indeed increasing in the Potomac and that theyre favorite food is Sunfish and topminnows.

Soo... *tries to understand* Does that mean that the introduction of snakeheads correlated to increased number of fish?

Edited by EricaWieser, 15 April 2011 - 12:08 PM.