Scientist: Frog's decline threatens Sierra ecology | High Sierra Topix  

Scientist: Frog's decline threatens Sierra ecology

Grab your bear can or camp chair, kick your feet up and chew the fat about anything Sierra Nevada related that doesn't quite fit in any of the other forums. Within reason, (and the HST rules and guidelines) this is also an anything goes forum. Tell stories, discuss wilderness issues, music, or whatever else the High Sierra stirs up in your mind.
User avatar

Postby burtonfm » Wed Feb 08, 2006 2:11 pm

This is a great thread and I'm learning quite a bit about the yellow legged frog. But, I do want to stand up for Caddis's entry because I had a similar opinion of the original post.

It appears we are all data driven people who form opinions based on our intepretation of facts and data. Great. I'm all for data and making statements that can be backed up by data. But, as I was reading the article in the original post, I was fine until the last few paragraphs. In particular, the quote: "I suspect that climate change is involved in general in these enigmatic declines" left me thinking Pounds was guessing. He didn't say "empirical data has shown" or "the consensus of the scientific community is"... he said "I suspect". To me, that's the equivalent of "I'm guessing that..." or "I really can't prove it, but I think...".

In the very next quote, he goes on to link the burning of fossil fuels to global warming and the emergence of the fungus, thus making a big leap in conclusions based on "suspect" logic. The article was about how fungus is impacting frogs, not an editorial on a personal opinion saying we are killing frogs all over the world as we drive our cars home tonight. In my opinion, Pounds's last few quotes cheapened the article and distracted the reader from the topic at hand. The article was about how frogs are disappearing from the Sierras, not a debate on fossil fuels. I can see why Caddis reached the opinion he did.

BTW, I found several well writen papers on the web that do a good job of disputing Pounds's assumption that the chytrid fungus is due to global warming. Bottom line... I'm not a scientist, so I'll let them fight it out and then I'll make up my mind.

I do love the Sierra's, and am all for restoring them to their natural state. I'm an avid fisherman, but have no problem supporting the frog restoration efforts, and now that I'm more aware of the problem (thank you everyone for the informative posts), I'll be watching for ways to help. I promise to catch as many fish as I can and eat them :>.



User avatar
burtonfm
Topix Acquainted
 
Posts: 21
Joined: Sun Nov 13, 2005 9:45 pm
Location: El Dorado Hills
Experience: N/A

User avatar

Re: Ribbet, ribbet

Postby giantbrookie » Wed Feb 08, 2006 6:02 pm

gdurkee wrote:Speaking only of the National Parks, most visitors & fisherfolk are pretty open and supportive of our netting a handful of lakes to reestablish habitat. It is such a major effort to get just a few lakes trout free that it's just never going to expand much in the forseeable future.


I believe most fisherfolk are supportive when they find out the comparatively small number of affected lakes. The problem has been that some sportswriters (and possibly magazine article writers) have fanned the flames of hysteria by greatly exaggerating the number of affected lakes. As a result, many fisherfolk are under the impression that an immense number of lakes will be gillnetted and they have no easy way to get a hold of specifics. Because I've been in touch with folks in fisheries management since the late 80's (initially starting with simply exchanging field data on fish populations with DFG) I've been able to find out things that the average wilderness angler cannot that easily. In fact, I myself have kind of fallen out of touch because my wife and I now fish less than 1/10 as much as we used to (having kids is main reason), hence less incentive to expend time mining various information sources. It also seems as if different groups are in charge of different restoration campaigns and one can't get all the info in one place. For example with DFG-managed programs, one pretty much has to go basin by basin. So the guy who might know changes in fisheries management policies for Desolation Wilderness won't know what's going on in the eastern High Sierra (JMW), for example. The DFG folks also won't know the extent of programs within the NPs and visa versa.

Speaking of which, what do you know about future gillnetting plans in Seki? I figured you are the one regular on this board who would know. According to what I've been told, efforts to date have focused on some unnamed ponds/lakes downstream of Helen Lake and some lakes in Sixty Lakes Basin. Is this still the situation, or have additional lakes had their fish removed (or will have them removed in the near future)? I know early generation plans targeted the remaining fishery in Swamp Lakes, and the unnamed golden-bearing lakes east of Bench Lake, as well as the big unnamed lake between Wanda and Sapphire (I had hoped the latter wouldn't get the axe given that it's Evolution's finest fishing lake, by far). Are these lakes still being considered for trout removal?
Since my fishing (etc.) website is still down, you can be distracted by geology stuff at: http://www.fresnostate.edu/csm/ees/facu ... ayshi.html
User avatar
giantbrookie
Founding Member & Forums Moderator
Founding Member & Forums Moderator
 
Posts: 2439
Joined: Wed Dec 28, 2005 10:22 am
Location: Fresno
Experience: N/A

User avatar

froggies

Postby AldeFarte » Fri Feb 10, 2006 12:53 am

Am I correct in assuming a large polliwog is likely to be a yeller leg and a small black polliwog in shallow , mud holes is likely to be a pacific tree frog? Or is this more of my ignorance? I read that article in the fresburg beehind and have to agree with caddis. I have known a few biologists over the years and and I would not accept any biologists study carte blanche. Every single one of them has an agenda. Fill in the blanks. I wonder who put that fungi down in the Costa Rican jungle that wiped out their froggie populations? Seems to me they have been experiancing global warming down there for quite a few MILLION years. My experiance with the word extinct is that it means KAPUT! No more. Gone from the globe. There are lots of places where the froggie is alive and well. I will concede that they are not thriving over their historical range. Neither is the buffalo or the elk. Yet they are not in danger of extinction. :D jls
User avatar
AldeFarte
Topix Regular
 
Posts: 215
Joined: Mon Jan 09, 2006 10:46 pm
Location: Eklutna, Ak.
Experience: N/A

User avatar

Re: froggies

Postby giantbrookie » Fri Feb 10, 2006 9:38 am

AldeFarte wrote:Am I correct in assuming a large polliwog is likely to be a yeller leg and a small black polliwog in shallow , mud holes is likely to be a pacific tree frog?

Small and black sounds like some sort of a toad polliwog. Tree frog tadpoles are fairly small and shades of brown. I recall tree frog tadpoles max out at somewhere around 4 cm in length including tail, whereas the MYLF tadpoles are also brownish but longer and fatter and can exceed 6 cm in length, although they're nowhere near as large as bullfrog tadpoles (15 cm range). As a little kid I used to raise toads and Pacific tree frogs from tadpoles in a backyard pond. All the ribbetting tree frogs must have kept the neighbors up at night, given that such as sound wasn't part of the normal nocturnal background noise in the neighborhood I grew up in.
Since my fishing (etc.) website is still down, you can be distracted by geology stuff at: http://www.fresnostate.edu/csm/ees/facu ... ayshi.html
User avatar
giantbrookie
Founding Member & Forums Moderator
Founding Member & Forums Moderator
 
Posts: 2439
Joined: Wed Dec 28, 2005 10:22 am
Location: Fresno
Experience: N/A

User avatar

Postby sierra_smitty » Tue Mar 07, 2006 2:17 am

SteveB wrote:GiantBrookie, is the database you referred to re: surveyed lakes in the Sierra online? Given some information seen here it would be interesting to examine the raw data from these surveys.



I was absolutely opposed to the whole "kill the fish to save the frog" thing until I took the time to educate myself about it, now I'm for it so long as the "powers that be" are up front about their plans, the when, the why, the where etc.

Some of the "science" out there truly is scary though..when you start off trying to prove something and your PHD or federal/state funding depends on you finding what you want to find, I'm sceptical, I think we all should be. Politics have as much a place in California's science as science does unfortunately......feel free to doubt it, but if you have your head screwed on straight, it should be no surprise. Lets just hope the best interests of those who actually enjoy these areas are protected when push comes to shove.....I'd hate to see some guy from NY who's never been here with a big smile on his face after his generous donation to some extreme enviornmental group helps close huge areas of our favorite playground to backpackers, anglers, photographers etc. I hope the day never comes when hiking or angling in the backcountry will be looked down upon...if you doubt it can happen, just look at what the pack stations are having to deal with, many would have them banned from the very trails they've blazed over the past 150 years.
Last edited by sierra_smitty on Fri Apr 21, 2006 12:05 am, edited 1 time in total.
User avatar
sierra_smitty
Founding Member
 
Posts: 50
Joined: Fri Oct 28, 2005 10:04 pm
Experience: N/A

User avatar

Postby gdurkee » Tue Mar 07, 2006 11:11 am

Well, as they say, it depends. Preliminary data is probably not available to the public -- that is, stuff that hasn't undergone peer review. That's kind of what science is all about. For instance, I was trying to put together a map last fall to demonstrate an area I thought should be next on the list to trap out the fish and restore it to frog habitat. I asked for the most recent data of frog & fish locations from our local biologist, who wouldn't give it to me because it was preliminary. I mean, I work for them and was doing an in-house project, but they still didn't want it out there until it had been published (plus, it wasn't his to give. The data had been collected by SNARL).

They (agencies and scientists studying froggies) definitely worry about people getting ahold of these maps, not to find the good fishing, but to reintroduce fish back to where they've been removed (once again boys & girls, that amounts to maybe 15 - 20 lakes in the entire Sierra). However, much of it is publicly available -- though I don't know where to get it. I think it's overstating it to say it's not available to the public.

Same thing with releasing information too early. Several of the researchers have generously written articles for Sierra Nature Notes, but have not felt that they could say things that they were pretty sure of but were not yet out there for peer review (in a science journal etc.).

My experience with all scientists (not just the frog folks) is that the facts lead them to conclusions. Overall, they're really bright and enthusiastic folks who just want to find out how things work. None of them go out to prove, for instance, that global warming is caused by humans. They do not have what a lot of folks here and in the popular press assume is an "agenda." The facts and models lead them to conclusions. No question there's a few with agendas, I just haven't seen it. Certainly not anywhere near the level that justifies the paranoid "they" are hiding stuff and have a hidden agenda... .

g.
Last edited by gdurkee on Tue Mar 07, 2006 11:22 am, edited 1 time in total.
User avatar
gdurkee
Founding Member
 
Posts: 658
Joined: Tue Nov 08, 2005 8:20 pm
Experience: N/A

User avatar

Postby gdurkee » Tue Mar 07, 2006 11:18 am

Speaking of which, what do you know about future gillnetting plans in Seki? I figured you are the one regular on this board who would know. According to what I've been told, efforts to date have focused on some unnamed ponds/lakes downstream of Helen Lake and some lakes in Sixty Lakes Basin. Is this still the situation, or have additional lakes had their fish removed (or will have them removed in the near future)? I know early generation plans targeted the remaining fishery in Swamp Lakes, and the unnamed golden-bearing lakes east of Bench Lake, as well as the big unnamed lake between Wanda and Sapphire


Giantbrookie:

Sorry. I missed your earlier post. As far as I know, the only lakes under consideration or where there's work being done are the ones below Helen (maybe 3 lakes??), 60 Lakes (and of them only 5 or so); the small lake NW of Golden Trout; a lake directly across from Golden Trout on the other side of the Canyon. I've never heard anything about Wanda or Sapphire as being under consideration. Seems really unlikely to me. The problem is you can't just do a lake -- you've got to make sure you get all the feeder streams free of fish, so you look for isolated lakes (at this stage) that have some sort of barrier (a 10 foot waterfall) to prevent fish from getting back. Kind of limits what you can actually do. You also want a basin where there's other lakes with frogs so if they're wiped out of one lake, they can repopulate from another. Finding such a combination is not easy.

It's a bummer the angler magazines get so amped up about this without checking the actual plans and what's possible... .

g.
User avatar
gdurkee
Founding Member
 
Posts: 658
Joined: Tue Nov 08, 2005 8:20 pm
Experience: N/A

User avatar

Postby giantbrookie » Wed Mar 08, 2006 11:17 am

gdurkee wrote:Giantbrookie:

Sorry. I missed your earlier post. As far as I know, the only lakes under consideration or where there's work being done are the ones below Helen (maybe 3 lakes??), 60 Lakes (and of them only 5 or so); the small lake NW of Golden Trout; a lake directly across from Golden Trout on the other side of the Canyon. I've never heard anything about Wanda or Sapphire as being under consideration. Seems really unlikely to me. The problem is you can't just do a lake -- you've got to make sure you get all the feeder streams free of fish, so you look for isolated lakes (at this stage) that have some sort of barrier (a 10 foot waterfall) to prevent fish from getting back. Kind of limits what you can actually do. You also want a basin where there's other lakes with frogs so if they're wiped out of one lake, they can repopulate from another. Finding such a combination is not easy.

It's a bummer the angler magazines get so amped up about this without checking the actual plans and what's possible... .

g.

Thanks for the confirmation. Indeed the big one between Wanda and Sapphire would be a major undertaking given that it has a whole system of feeder streams that are teeming with fish. The one you are referring to across from Golden Trout, I presume is Mesa? I heard both Mesa and Knob were gillnetted. I recall that are more JMW lakes slated including Bench (Onion Valley) and the upper Treasures in Bishop Creek.

Regarding your reply above about information, I agree about the reluctance of scientists to divulge data that is not part of peer-reviewed literature. Given that I am a research scientist myself I can say that it is certainly part of our normal cautious approach and what we feel to be public responsibility. As you may know, there have been a lot of missteps when scientists have gone to the press or general public before their work gets published in a rigorous peer-reviewed forum. "Cold fusion" is one of the most infamous examples. In the SF Bay area there was a notorious case of this back in the mid 90's when a loose cannon geophysicist went to the press with his interpretation that there were a gazillion active faults in the SF Bay. I benefitted mightily from this because I received research funding for two years to hunt down the on-land projections of what turned out to be phantom features. When other geophysicists finally saw the data that the interpretations were based on, the whole thing quickly evaporated, but the issue wouldn't have been such a cause celebre had it gone through the standard peer reviewed channels first--the work (ie original interpretation) would have never been published.

I also sympathize with the sensitivity of researchers to the issue you pointed out about clandestine fish stocking. Living in the era of fingerling air drops it's easy to forget that the original stocking of Sierra lakes was by coffee cans and other low-tech manual means. McDermand himself even writes about doing this (the nice goldens in Darwin Canyon may be part of his legacy in this respect).

The bottom line is that the total number of affected lakes vs those that still have fish is vanishingly small, so it has a negligible total effect on the quality of Sierran fishing. The adverse fishing impact has been dramatically overstated in magazines, newspaper articles, and in Cutter's 2nd edition.

We should also bear in mind that this lake-kill info is not the only information that is not easily accessible by the public. The basic DFG air drop allotments/schedule/distribution data is not easily accessible either. The only reason I personally got to see that information was that I exchanged data with DFG over the years (in the pre-frog era when DFG wasn't getting much funding to do field studies).
Since my fishing (etc.) website is still down, you can be distracted by geology stuff at: http://www.fresnostate.edu/csm/ees/facu ... ayshi.html
User avatar
giantbrookie
Founding Member & Forums Moderator
Founding Member & Forums Moderator
 
Posts: 2439
Joined: Wed Dec 28, 2005 10:22 am
Location: Fresno
Experience: N/A

User avatar

Frogs vs. Trout? It's a red herring...

Postby avidskier » Sat May 27, 2006 2:56 am

I've been discussing this topic off and on for a couple of years with a friend that works at the Fish and Wildlife Service. There are a number of factors that don't quite seem to add up.

Trout have been nearly ubiquitous in the Sierras since before World War II. Read books from that period, such as "Waters of the Golden Trout Country" and "Yosemite and Kings Canyon Trout" (1946 & 1947 by Charles McDermand), which document both broad distribution and much healthier populations of native and non-native trout in the Sierras, yet yellow-legged frogs apparently thrived in the face of that evil onslaught until just recently. Why do researchers not explain the disconnect between the broad stocking of trout, as well as prior much higher populations of trout in the waters they inhabit, and the much later (by many decades) decline of the yellow-legged frog? It's a glaring oversight in the overly simplistic cause-and-effect theory that trout are a primary cause of the frogs' decline.

There are other holes in the "trout as cause" theory. According to one of the primary researchers on the decline of the frogs, Roland A. Knapp of the Sierra Nevada Aquatic Research Laboratory:

"The combination of data from Wallis (1952) and Botti (1977) suggests that approximately 34% of Yosemite National Park lakes still contain fish (Elliot and Loughlin 1992)."


Is it reasonable to conclude that the water-bound residents of 1/3 of an area's lakes are responsible for a species' decline across the entire area?

Let's agree for a moment with D. Knapp's theory that introduced trout are a primary cause of frog decline, and see what he says about another area receiving attention, Kings Canyon National Park:

"However, a considerable amount of inter-drainage variation in the relative proportions of fish-containing versus fishless lakes is apparent from a second survey by Bradford et al. (1994a). This survey included 104 lakes in a particularly remote portion of Kings Canyon National Park, and trout were only found in 17%."


Wouldn't we all know a lot more about frog decline if we studied what's threatening them in the 83% of that basin's lakes that don't contain trout?

I do believe that trout have some impact on frogs, where trout are found, but surely native predators such as garter snakes, birds, and coyotes are much more mobile and ubiquitous threats across the frogs' range. Some combination of environmental causes is tipping the scales and denying these predators their froggie dinners across the frogs' entire range. Focusing on trout, found in a minority of Sierra lakes (and native to many of those lakes), only sucks research dollars as well as researcher and volunteer resources away from the greater underlying issues.

So why, you might ask, would a researcher do this? In parks and wilderness areas, researchers can get grants to study and remove non-native species. The process begs for an easy scapegoat. By highlighting only the trout "issue," bioligists can continue to get paid to spend summers camping in beautiful remote areas of the Sierras, gill-netting and removing trout (which according to the numbers they provide affects somewhere in the range of only 17-46% of Sierra lakes). Nice work if you can get it. One biologist has made a tidy living from this theory for over a decade. Doesn't he have to release supporting "findings" to reinforce the valuable expenditure of last year's grant, and to set the stage to get awarded next summer's grant funds? It appears to be a treadmill that's hard to get off of, and at some point, perhaps even when a theory is first offered, a researcher's professional reputation may get caught up in justifying and furthering the theory.

With so much drama and momentum built up around that theory, now even the lack of a quick rebound of frogs in the trout-cleared lakes must be blamed on the removed trout (they damaged the ecosystem so thoroughly). Now the problem HAS to be the trout. Now more than ever.

A much more balanced view of frog threats is presented at sites such as: http://eces.org/archive/ec/ecosystems/a ... ml#sources
The problems facing amphibians are global and multi-faceted. The fungus killing yellow-legged frogs in common in soil, not some new exotic invasion, and it is a documented factor in amphibian declines and extinctions as far afield as Australia and South America.

What else could be involved? Naming global warming and UV radiation as contributing factors seems like a bit of a cop out: they're too trendy and they're a convenient shift of blame and response away from local action. Deformities in frogs may be linked to viruses. What are we going to do, vaccinate amphibians? The decline of mountain yellow-legged frogs may be linked to the use of pesticides in the Central Valley. See the work by Gary Freel (spelling?) of the USGS. Pesticide use issues would require entering the arena of the EPA registration process - a real "can of worms" especially under the present administration. If you were successful providing information justifying the need to ban or more closely control some chemical applications, you would be assailed on the economics. What would be the effect on agricultural output? On jobs?

Unfortunately too few Sierra lakes have trout to have their removal make much of a difference either way to the frogs. Through the siphoning off of valuable research dollars some underlying decline factors may go relatively unexplored and unaddressed. We may see another decade of trout-targeting papers (how the trout destroyed lakes long term, even when they're no longer in habiting those waters) before that horse is thoroughly beaten to death.

My bet is on mercury. Rain arrives on California's shores with 300% the estimated pre-industrial level of mercury, and due to interaction with ozone once it starts inland contains 44% more mercury when it falls inland. Methylmercury is toxic to tadpoles at concentrations of .05ppm (Chang, et al 1973), can build up in vertebrates to concentrations many thousands of times greater than mercury levels in the surrounding water, and can be a greater problem in clear bodies of water with low dissolved organic matter (Gorski 2006).

Effects of methylmercury chloride on Rana pipiens tadpoles
http://www.sciencedirect.com/science?_o ... 55f3157c63

Mercury From China Rains Down on California
http://www.evesgarden.org/archives/2002 ... California

Study shows link between clear lakes and contaminated fish
http://www.engr.wisc.edu/news/headlines/2006/Feb15.html

Up to 83% of the mercury load to the Great Lakes comes from atmospheric deposition (see Shannon and Voldner, 1995).
http://www.epa.gov/owow/oceans/airdep/air2.html
User avatar
avidskier
Topix Newbie
 
Posts: 1
Joined: Fri May 26, 2006 10:04 pm
Location: Sacramento, CA
Experience: N/A

User avatar

more ribbetting

Postby gdurkee » Sat May 27, 2006 11:07 am

Hmmm. Not sure where to start here. I'll start by agreeing with you. Yes, there are definitely other factors affecting froggie decline. Two things seem to be going on. At a macro scale, frogs are being eaten by fish. Period. Specific lakes that have fish don't have frogs. Find me a lake that has fish AND a substantial frog population (over, say, 50 adult mountain yellow-legged frogs). You can't do it. You can, though, find lakes with healthy frog populations (200 to over a thousand) and no fish. Kind of a clue to what's going on.

It's important to distinguish the individual lakes, not just a blanket: "83% of lakes in XXX." How many of those lakes are actually suitable frog habitat? It's not a hugely meaningful statistic. More importantly, you're wrong that the frog populations don't rebound when the fish are removed. In every case that I have personally witnessed in Sequoia Kings (about a dozen lakes now) the frogs are back immediately (like in weeks) and in very large numbers where they didn't exist before. In hiking for 35 years in Yosemite and Sequoia Kings, I have never seen significant populations of frogs occur where there are fish. Maybe one or two frogs, but not dozens or hundreds as occurs immediately upon fish removal.

But, you touch on an issue that the researchers are definitely interested in and absolutely not ignoring, as you imply: Why is this happening in the last 30 years? You're absolutely right that fish have been around since the late 1800s when they were introduced in alpine lakes -- which had NO fish before then (and I'm only talking about elevations above about 9,000 feet where there were almost no lakes between Northern Yosemite and southern Sequoia that had fish before they were introduced -- I'm less sure of distribution outside those areas).

Next, and here you're very likely right, is the micro scale. Something else is for sure happening. Frogs are clearly dying for other reasons. In those frog populations that have mass die-offs, Chytrid is usually present in all of the frogs. You're right that it is present world-wide, but it has only shown up in the last 10 (??) years in Sierra frogs. It's also not at all clear that it even existed in the US much before then. It is likely a new pathogen to our populations of frogs.

The biologists are now looking at what makes them susceptible to this fungus. My money, too, is on airborn pollutants. The worst Chytrid outbreaks have been in areas of Sequoia Kings that have the worst (to my eye, but also actual pollution data) visible pollution -- the Kern Canyon and along the west slope of Sequoia Park (Tablelands, Pear etc.).

Also, it appears (and I'm on shaky ground here) that the frogs that succumb to Chytrid are already weakened prior to visible infection -- they show very low fat content. Also being looked at is skin secretions that fight infection. Something may be happening at the molecular level that compromises this system in the mountain yellow-legged.

I think part of the problem is that you and others seem to be focused on one cause. At the moment, the one thing that can actually be done to at least preserve the frogs in small areas is to take out the fish in a drainage that the fish can't get back to. That at least preserves the frog populations for those areas and preserves a reservoir for them to recolonize other areas. This is critical to their survival. I think the accelerating decline has been because when one population is wiped out by Chytrid (or other pathogens that have been documented), there are no longer nearby populations to recolonize as would have been true in the past. It is almost certainly the trout that have started that vicious cycle.

I tried that link with the "balanced" presentation. It seems to be blank. Also, I'm more than a little confused by you saying that "Doesn't he have to release supporting "findings" to reinforce the valuable expenditure of last year's grant, and to set the stage to get awarded next summer's grant funds? It appears to be a treadmill that's hard to get off of, and at some point, perhaps even when a theory is first offered, a researcher's professional reputation may get caught up in justifying and furthering the theory."

These guys publish in peer-review journals. Sure, they could probably get away with shoddy data for awhile. But all of the data by a number of different researchers is showing the same things. The predictions they make are being borne out by field experiments. It's all agreeing internally. That's what science is all about. Taking a swipe at them because "biologists can continue to get paid to spend summers camping in beautiful remote areas of the Sierras, gill-netting and removing trout" is specious black-helicopter nonsense. The initial work on frogs & fish has led directly to current research on Chytrid and airborne pollutants -- they are not ignoring, covering up or tweaking the data so they can spend time in the backcountry floating in alpine lakes. They are following the data.

Many of these researchers have generously submitted articles to Sierra Nature Notes. Check out the Archives section at http://www.yosemite.org/naturenotes.

I remain, respectfully,

George, Defender of Frogs
User avatar
gdurkee
Founding Member
 
Posts: 658
Joined: Tue Nov 08, 2005 8:20 pm
Experience: N/A

User avatar

PS

Postby gdurkee » Sat May 27, 2006 11:10 am

PS: AvidSkier. I'm not sure, but I think your long link (Effects of methylmercury chloride on Rana pipiens tadpoles) needs to be broken in half -- or even thirds. It may have caused the margins to widen beyond what they usually are. Maybe you could edit it and see if that helps to keep the lines wrapping in a reasonable width.

Eric, does that seem like what's happening?

Thanks,

George
User avatar
gdurkee
Founding Member
 
Posts: 658
Joined: Tue Nov 08, 2005 8:20 pm
Experience: N/A

User avatar

Postby giantbrookie » Sat May 27, 2006 11:22 am

Avidskier, you bring up some good points and have clearly spent some time researching this. Knapp and fellow researchers are well aware that trout are not the sole cause for the decline of the MYLF. Unfortunately, trout are probably the easiest of the several identified factors to tweak in an effort to protect the frogs (ie it's much harder to mitigate against the fungus and the larger scale environmental factors are similarly more difficult to control at this time), so the trout have been left to take the fall. If you've seen the trout distribution versus frog distribution maps, I think it's pretty difficult to deny that trout have had a negative effect on MYLF populations. Regarding the 34% (Yosemite), it is important to think about the last part of that sentence "...suggests that approximately 34% of Yoseemite National Park lakes STILL contain fish..." (my emphasis there). The number of lakes that once held trout prior to cessation of stocking is vastly greater. Large numbers of rainbow-trout stocked lakes in northern Yosemite have gone fishless, for example (Flora, Spotted Fawn, Boundary, Inferno, etc). The same is true of Seki, where many lakes have gone fishless in the past few decades. Thus the majority of lakes deep enough to support trout (and this is sort of similar to the lakes that will support MYLF because their polliwogs need to overwinter) in the NPs probably had fish at one time, just as the vast majority of lakes in the areas surrounding the NPs do (or at least did until very recent changes in stocking policy).


Regarding the history of coexistence of trout and MYLF, I think there is no question that in many fisheries the trout did indeed wipe out the MYLF. McDermand's own accounts provide anecdotal evidence for this as there are a number of accounts of obese trout gorging themselves on polliwogs and you know what kind of poliwogs those are. At present most of the southern Sierra lakes with coexisting MYLF populations and trout have very low trout population densities (this means very nice sized trout, by the way).

I am personally aware, however, through 40 some odd years of hiking about, of examples wherein the trout's presence cannot be held responsible for the MYLF extirpation in a given lake. At Vogelsang Lake, a lake that had held trout for decades as of my visit there in 1969, I saw lots of MYLF polliwogs. In fact, given that the fish were lying low that day, I thought it meant there weren't any fish! Similarly at Mildred Lake in 1979 I saw plenty of polliwogs and the apparently abundant brookies were laying low at the time. Like Vogelsang, the fish and Mildred and frogs were apparently doing well together for a very long time, but it is likely that something else did them in .

The southwestern Seki high country has a number of lakes that certainly don't have fish today, and I suspect there is at least one remote, trailless, major basin that never held trout (potential spawning looks too good for there not to be fish it fish had ever been introduced). These lakes lack MYLF too, again pointing to another culprit for their extirpation there.

In Desolation Wilderness MYLF populations still exist in lakes that have held significant trout populations for decades; some of these lakes have or have had very high trout population densities. In fact most of the MYLF lakes in Desolation are trout-bearing lakes, in stark contrast to the pattern in the higher altitude central and southern Sierra.

Again, there is no question that trout are not the only culprit in the decline of the MYLF, but the data, at least in the central and southern Sierra that show a very good correspondence between trout bearing, MYLF absent, and trout absent MYLF bearing lakes makes a good case for trout having had a major detrimental effect. As an avid fisherman, I don't like to see the trout get scapegoated, but I don't think I can deny the strength of the data, either.
Last edited by giantbrookie on Sat May 27, 2006 12:10 pm, edited 1 time in total.
Since my fishing (etc.) website is still down, you can be distracted by geology stuff at: http://www.fresnostate.edu/csm/ees/facu ... ayshi.html
User avatar
giantbrookie
Founding Member & Forums Moderator
Founding Member & Forums Moderator
 
Posts: 2439
Joined: Wed Dec 28, 2005 10:22 am
Location: Fresno
Experience: N/A

PreviousNext

Return to The Campfire



Who is online

Users browsing this forum: Google Adsense [Bot] and 1 guest