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Dean Hendrickson  






Biology discussion  

Interview 17:46 - 1:26:04 Play 17:46 - More
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Dean Hendrickson  






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Water flowing, swimming  







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Dean Hendrickson  






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Swiming, snorkling sounds  







NPR/NGS Radio Expeditions
24 Jul 2001

  • Mexico
  • 26.98369   -102.04739
  • Stereo
    Sampling Rate
  • 48kHz
    Bit Depth
  • 16-bit
    Equipment Note

Show: Cuatro Cienegas
Log of DAT #: 4
Engineer: Fox
Date: July 24, 2001


In the bg JB screams out - WHAT IS THAT OLD BLDG?

3:28 DH - it is an old house that has been here since the 1880s or something - somebody used to live out here - and this used to be a bath spot - a popular bath spot

3:46 getting out of jeep - slam of doors

FX 3:58 open trunk (off mic - JB - man it is dusty)

4:25 getting gear, etc. quiet ambi - not much going on

talking off mic

5:09 DH - the boil is right there in the deepest part and it is coming up almost body temperature - cooler than body temp - and this big canal was built - we are not exactly sure when, but some 1920 photos indicate it was in there by then

JB - they would have used steam-powered shovels?

5:35 DH - I think the first time it was built it was probably dug by hand, and then later they clearly used heavy equipment for it 5:41

5:48 DH - what is it (looking at a bird) a red tail? Hum there is goes, right behind the trees. Huh.

5:56 DH - well the water levels - this is an old bath house. This place was popular as an old bathing spot supposedly the mineral content here and the mud was good for people's health. People used to come all the way out here way way back when to bath here for medicinal purposes. And this bath house was constructed after at the former water level so that the women wouldn't have to get out of the water to get into the bath house. So this is the old water level. So it has been lowered at least 2 meters or so. Like I said in the 1920 photos show that it was at least a meter higher and there was a smaller canal in then. And then the canal was deepened and the water level dropped more then. And the canal was deepened and the water level dropped even further. And even before that, before the first canals it looks like - if you look at this flat around the house there is some old travertine which indicates that there used to be shallow surface flows all over this area here. And if we walk up towards the mtn there were just little shallow cienegas, little marsh lands, all along the side of the base of the mtn which have now mostly been drained through little canals that connect up in to like this one which brings in a fair bit of cool water that is draining these superficial wetlands up higher. And then of course all of these little canals come together into big ones. And this canal was built with the intent in taking the water out to the Rio Mesquites which is then captured in bigger canals like Sacasaladas and the water goes out through - where you drive in through Moncolva. 7:39

8:23 DH - if the mineral content of the water was lower here that surely there would be a city on top of this right here. If this was nice fresh drinking water there would be a large city in this valley. but bc of the high mineral content of the water it is relatively useless, certainly for domestic purposes. Industry has tried to use it; it has been very corrosive, and in agriculture you have to irrigate at very high rates to deal with the salinity, so it is not very useful water, and therefore there is still water in the CC basin 8:52

8:58 JB - so its mineral content has saved it from extinction in some ways.

DH - yes. Correct.

9:14 DH - you get a wide range of water quality throughout the basin though. There are springs which are much fresher than others. This is fairly high mineral content here. It seems like all of these coming up from the deep aquifer through fractures along the fault zone are more highly laden with minerals and usually warmer. It is clearly come up from great depths. 9:34 but this water coming off the cienegas here is more fresh, and probably more useful for agriculture. You see evidence of agriculture up high, all along the edges of the basin indicating that there used to be much more water up high and people were ditching it and irrigating fields with it, but now the water levels are well below those old fields.

JB - hotter spring water indicates that it come from deeper in the earth. And or along fault zones where it might have contacts with igneous rocks. There is some volcanic activity in the area. Not too far north you find volcanoes - up by El Campo¿..\

10:50 JB - (kidding around) a cool 85 in the water!

10:53 DH - it is more like 95 probably! Yeah, it is right up there¿ is way up there¿.

11:03 DH this water coming in is quite a bit cooler and we often see that the fish like to hang out there especially in the summer.

11:18 JB - well, whatever the temperature, let's get in the water!

DH - OK. Good.

12:30 Shawn walking to the poza

13:03 ambi by the side of the poza - Shawn setting up the mics - so not great ambi

14:28 Shawn waist deep in water - waiting for JB and DH to come down into water - ambi - with faint talking (of JB and DH) in bg

15:56 - 16:07 splashing around in the water

16:53 ambi - walking up to poza - very quiet¿.

17:49 - JB - is it bath-like?

18:11 DH This pool clouds up really easily, this is really loose sediment, so the way to get in right here where there is not a whole lot of sediment and if you just keep your feet up and pretty much float you will maintain pretty good visibility. 18:24

JB - ok.

18:39 DH - but if you kind of walk in it really clouds up pretty quickly

18:42 ambi

18:51 JB - lead the way

19:10 JB - oh this isn't bad

FX 19:11 DH jumps in - and swimming around

19:43 JB jumps in - swimming around

JB - is this one of your favorite pozas?

21:41 DH (talking with his snorkel mask on)- yeah this is clearly one of my favorite pozas. It is one of the warmest in the valley¿¿but it also has some rather unique features to it. It has very much changed. That is one of the reasons we choose it for one of our study sites. It lacks exotic species and it is isolated. The canal was never a success. The canal was eaten by a sink hole about 2 ½ kilos down stream¿ the fish fauna is isolated, and we thought it was one place we might be able to successfully conduct a mark recapture and get a good population estimate. And it turns out it is true. In the poza here when we come back to capture recently we find that 60 to 70% of all fish in here already carry our marks. We have a large percentage of the population marked and we are starting to get very good data on growth rates and movement, mortality rates and all that sort of stuff that we need to really understand how these populations work. 22:57 some of the other things we are finding out - just recently one of our colleagues from the U of New Orleans in La has been working out hereon the snails and suddenly we find out that this pool is the only one that has an all female population of the endemic snail. The nexi pergus (sp). It is not that uncommon that you find all female populations of snails, but this is the first one we found in the basin here. So there is something unusual going on here, but we aren't sure. 23:31

JB - what else is interesting here?

23:36 DH - the extent of modifications is clearly interesting. This one of the first ones that was modified. This canal went in probably around the turn of the century, we don't have the exact data, but it has been modified for a long time water levels used to be 2 or 3 meters higher historically, and then canal came in and the water levels were dropped, and so it is clearly a modified system, it still maintains the native fauna, and it also offers an interesting clime in temperatures. We are interested in looking at the movement of fishes. We have never seen the cyclids reproducing in this poza, and they must seek out cooler temperatures. We do see reproduction going on further on down stream, so it seemed like a good place to look for evidence that these fishes do seek out certain temperatures in which to do their spawning. 24:26

24:24 JB (off mic) it doesn't feel as hot as I thought it would feel

DH - naw - no it is just that it is so warm outside.

JB - it is still pretty refreshing.

24:37 DH - but you notice how much sediment is in here. This sediment is just loaded with snails. In fact some of the highest snail densities we ever found were in this pool. We find up to 40,000 snails per square meter. It is just really thick with snails. The other interesting thing - (JB - tiny snails) the little tiny endemic snails - right. We are studying these fish that are polymorphic. One form of the species eats snails. The other one feeds on detritus and can't eat snails, and so that high snail density is interesting, especially in light of the fact that we find that there are always no molluskavores (sp) the snail eating form is very rare here. And we don't really know what is going on here. The snails in here - it looks like related to water temp, have a relatively soft shell. So maybe they can eat snails w/out having the malara (sp)¿.. 25:30 so there are number of questions that drew us to this particular poza. Not to mention that it is fairly isolated, doesn't get a lot of traffic here and we can do things like these cage experiments here w/out having them messed around with much¿¿

JB - are these cage experiments the same as Jane's were you have exotic - and native duke it out?

DH - We don't have any exotics in this pool¿.

25:57 DH - these are experiments in which we are looking at the effect of fish density on snail densities - interactions of native fishes and native snails, so that these are manipulating the densities of snails and fishes.

SHAWN changing locations

27:50 JB and DH diving down
28:20 - 28:23 blow! (from snorkel)

28:24 DH - ok, it is a little bit stirred up bc of the sediment we were on over there. But basically - you saw me grab on to that shelf? you saw some of the big cyclids ? under there? It is real interesting . we got to come back and use some different techniques. It seems like our fishing techniques - we typically just sample with hook and line. And look pretty clear that we are missing the big cyclids. We tagged the first time we came here. And we have to pay more attention to how we capture them. It gets a little more difficult to get nets down into this broken rock that you saw down there. But we have some big fishes that we are not catching so we have to come back and use some diff techniques and see if we can get them. You might have seen the coke bottle down there with our temperature data logger (a description of this¿¿) and it is a pretty constant temperature¿.. with a temperature that is getting up close to body temp that is coming up out of the spring boil. And you can see the snail shells bubbling up a little bit, and the alga that is bubbling up with it 29:28

JB - so what is the spring boil?

29:32 DH - The spring boil is where the water is coming up from the deep aquifer. You get alignments of springs kind of paralleling the mtns. it looks like the water is coming up along faults to the rising of the mtns and things like that . it is coming up pretty deep, increased temperatures, highly mineralized - it is probably water that has been underground for many hundreds or perhaps thousands of yrs. We are not sure. The hydrologic studies haven't really been that thorough yet, so we don't know that much about the aquifer. 30:01

JB - Can you date water?

30:05 DH - there are ways you can date water. It hasn't been done here yet, but you certainly can¿¿¿.

30:15 JB - but you think that the water that is coming up in this pool, where you are floating, is 1000 yrs old?

30:23 Dh - like I said I have no idea, but I am quite sure that it has been down there quite a long time. It is highly mineralized, meaning it has been in contact with the rocks for a long time. It comes up warm meaning it's been down deep, along a fault where is a little bit of volcanic warming

30:40 JB - so why don't we get a little closer and talk about¿..

30:51 JB - oh boy this is really mucky!

DH - this is really mucky.

31;16 JB - this is like walking in quick sand!


DH - it is actually all snail feces is what you are actually walking on ¿.

JB - oh, now I am feeling the snails.

DH - incredible high densities here at times¿.there are lots of snails in this stuff - these are the endemic snails¿ that are such an important part of the ecosystem here¿.and you get this whitish clay here which I think has something to do with bringing the water to the surface here 31:50

31;51 JB - So this really fine silt that we are standing in is not such much plant detritus as - what/

DH - snail feces - as I was saying - it is processed¿¿¿32:24 over millions of years basically these big deposits of snail feces have built up here and they are really an important part of the ecosystem, there is no doubt about it. 32;32

32:53 DH - my name is Dean Hendrickson. I am the curator of ichthyology at the Texas Memorial Museum of Science and History at the University of Texas in Austin, and we are sitting here in the middle of Chihuahuan desert - really literally, about in the center of it, in a nice warm poza called poza Escavada in the middle of the CC valley. we are here talking about the endemic fishes and snails and basically the ecosystem studies we are basically trying to understand how this ecosystem works. It is now a national park in essence a protected area for fauna and flora, run by the federal govt of Mexico and they developing a management plan and trying to figure out how best to manage this ecosystem about which we know relatively little. 33: 34

JB - why are the lagoons of CC so unique in the world.

33:44 DH - the biggest thing would be the high rate of endemism here¿

34:16 DH - poza Escovado is an interesting poza though it has very much changed from historic conditions but basically what we have here is an almost circular sink hole in the middle of a flat desert valley surrounded by very much desert vegetation and then suddenly this round sink hole in this beautiful crystal clear blue water coming up from a deep crack in the earth full of the endemic cyclid fishes and snails that we are studying here. I like it here bc it is an ideal study site. For one we have this modified system but it still maintains the native fauna. It is an enclosed system in that the water goes a little bit underground down stream and so we have a sort of captive population that we can study in great detail. It is unique in some ways in the valley for having the highest densities of snails, low abundance of the molluskular form of the polymorphic cyclid - a number of different things that interest us here. 35:15

JB - have many times have you been to CC

35:26 DH - whoh that is hard to say. I first came with my advisor, Dr. Minckley, in 1978 or 9¿.since then the place really caught my attention and I came back on average every couple of years, at least once. Moved to Texas in 1990 and that gave me much better access to the place - cut my travel time in half, and I started bringing my ichthyology class down here for a yearly field trip. I came down here at least once yearly since 1993, and any more now I come down 10 - 12 times a year.

JB - So since you have been coming down in 1978 has the beauty of the place still affect you?

36:03 DH - oh certainly, it is a gorgeous place. It is an amazing place. I think the beauty requires a little bit of education and training to really appreciate. I have come down with a lot of people - especially scuba divers thinking maybe they are going to be [GG log] diving in this incredible place and they come down and see these little holes in the ground and go, "Hey, big deal." The perception is clearly depends on the person. But it is a gorgeous place - the desert is amazing around here - incredibly high diversity in the terrestrial systems and then you get into these amazing aquatic systems. The endemism is very high, diversity is quite high for desert aquatic ecosystems, and just fabulous places.

36:50 JB: So - what is it about CC that sets it apart - that has drawn so much int'l attention scientifically and ecologically?

36:58 DH - The big thing that sets CC apart and has drawn so much attention to it I think initially at least was all of these species which are found here and nowhere else. Obviously biologists discovered that and the questions were "Why here? What's so special about this? How did all these things evolve here?" I've been meaning to do the calculations for some time¿but if we compare it to something like the Galapagos Islands I think here we probably will find that on a per-area basis we have nearly comparable rates of endemism. Just incredible numbers of organisms which occur here and only here just like in the Galapagos. So that is what initially attracted biologists to the place. And then things like this polymorphic cyclid which is a big evolutionary quandry - how can one species have all of these different forms but still be one species. We have one species here which has at least two or three different morphs which do very different things in the ecosystem. They essentially function as distinct species yet they are just one species. And ecologists and evolutionary biologists have long been interested in how this evolved and how it continues to be maintained. Many people have claimed that this is speciation in process, kind of incipient speciation - this polymorphism is a step towards this morph becoming separate species (38:20)

JB: So in a sense we're watching the process of evolution as you watch these polymorphic cyclids.

38:28 DH - Certianly..things are always evolving..but this is apparently sort of a unique case. There aren't that many instances when you have this polymorphism¿and it's been proposed that this is an intermediate step towards their becoming species. (38:45)

JB - What are you trying to learn about these sinkholes?

38:53 DH - Our particular project right now is sort of, we're actually funded to try to figure out how these ecosystems function with the look towards that helping to preserve them¿and that's really the thrust of our project at the moment. We're trying to understand the food web - who is eating who, who's living on what - so we know how to manage these things, and on top of that, tie it into changing water levels. What happens to these pozas as the water level drops - what can we expect to happen, what components of the ecosystem will drop out first as they dry up. And then what will the cascading effects be¿because they definitely¿have been drying up for a long time.

JB: What's happening over time with the water supply to these sink holes?

40:00 DH - What we've seen here is over time people have been exploiting this water in many ways as you would expect in the desert¿.the water quality is not that high and often they have been thwarted in their attempts to use it. But their attempts to use it have resulted in a dropping of the water table so that we find many pools now have dried up, they've been ditched and the water is slowly working its way into those ditches, the water level drops, the ditches therefore flow that much less¿ every day less and less water is going down the ditches. The sort of superficial water table in the valley has definitely been impacted and many pozas have been dried. This one, for example, has been dropped two or three meters in water level. (41:05)

JB: So, the sink hole we're sitting in used to be two or three meters higher (DH - Correct) - a half a century ago?¿

41:17 DH - Probably more like a century or a little bit more ago. This was one of the first canals built. I don't know exactly when the first canal went in but by - we have photos from 1920 and at that point it looks like the water level was one to two meters higher than it is now. So there was a small canal that took water out of here then. Since 1920 the canal was deepened and the water level dropped that much more. So it has a long history of people extracting water from it (41:58)

JB: So what would happen to these lagoons if the area were not protected?

41:57 - If it were not protected, I'm sure that eventually everything would just dry up. Water in the desert is a very valuable commodity, obviously. We don't know exactly where this water is coming from but it clearly has its origin in the surrounding valleys and mountain ranges. And there's lots of agriculture going in. We see irrigated groundwater-based alfalfa agriculture in valleys both north and south of here. And I'm sure - the studies have not been done yet but clearly, I think, it's obvious that the origin of this water has to be in this valleys or other surrounding areas and if people are punching down wells and pumping out groundwater, that's probably groundwater that's not going to make it to CC and these pozas will just continue to dry up. (42:40)

42:58 JB: ¿Do you find these kind of freshwater pools with the high concentration of endemic species in any other deserts in the world?

43:04 - DH: Oh certainly, yes. Obviously springs like this are sort of islands in reverse, basically. They're aquatic islands in the middle of the desert, and anywhere you get isolation like that you tend to have endemic organisms evolve. They're isolated from their relatives and they evolve into unique species. So it's very common to find endemics in springs. You find them in other deserts around the world. In particular, the Chihuahuan Desert seems to have a high number of spring endemics but like here - in fact perhaps the rest of the Chihuahuan Desert has been more impacted, there are many many dried springs and extinct species scattered throughout the Chihuahuan Desert. Water has been exploited for agriculture and these springs have been dried up or otherwise modified and species have gone extinct. CC is unique in having a very high diversity and lots and lots of springs so there's a higher level of diversity than you'd find in other spring ecosystems in the Chihuahuan Desert. (44:04)

JB - But what about other deserts in the world?

44:47 - DH: Oh, certainly. There are oases, for example, in North Africa and other parts of the world where you definitely find endemic species. (JB - You've been to them?) I haven't been to those in particular. I've traveled mostly in the deserts in North America. I've done a lot of work in the Sonoran Desert. Springs are very very important habitats in the Sonoran Desert as they are in the Chihuahuan Desert. A lot of the endangered species, for example, in Arizona are spring forms that have been impacted by - same sorts of things - overexploitation of ground water - various things that have caused the springs to dry up. Exotic species are a huge problem - we have them here at CC. They've more recently arrived here than in other areas. Arizona has had exotic species impacting its endangered fishes for years and years. (44:55)

JB:¿ (45:00) There should not be African ornamental fish in a sinkhole in Northern Mexico.

45:08 DH - Most definitely not. We have no clue how they came to be here but it looks like some aquarist from somewhere was driving through CC with some of his African jeweled cyclids with him and decided, "Well, this would make a nice home for my fish" and released some here. They've managed to find their way around the basin. It looks to me like humans have moved them in some cases. Some of the pozas we've found them in, we can't figure out how they possibly could have gotten there naturally. So it looks like humans have moved them around a good bit and they're clearly going to have an impact on the native fauna here. (45:40)

JB - Even though they look - even though they make for a better experience when you're snorkeling¿45:55 DH - Even though they're pretty fish, I'd just as soon they were not here. ¿ Our experiments, though, indicate very clearly - our isotope analysis, our stable isotope analyses, and our cage experiments and all that are indicating very clearly that they do live on the same things - they overlap in the food web - with the young cyclosomal somethingorother. And with the pup fishes as well. They clearly will have their impacts -we haven't documented it too thoroughly yet - they haven't been here that long. So I don't think we've seen their impacts in terms of changes in the populations of the cyclids¿ There is one poza which looks to be one in which they were first introduced and the local people tell us it used to have the native cyclid. It does not any more. It could be that the jewel cyclid caused the extinction of the endemic cyclid, but it's a highly manipulated pool so it's a very small little spring, it's highly manipulated for agriculture and there could be other reasons why the native cyclids went extinct there. (46:57)

JB - But that's one of the things you're trying to find out?

47:00 DH - Yeah, exactly. We want to rigorously understand, do studies to demonstrate how these things are going to interact. Is hemichromus, the jeweled cyclid, really a threat to these fishes. It could be that it could exist here and not have a terrible impact on the cyclids. Our preliminary data indicate that it probably will. (47:19)

JB - And, I have to ask this question, why should people thousands of miles away¿care about what happens to CC?

47:35 DH - I think it really is a world class resources. We have incredible biological diversity here in the middle of the Chihuahuan Desert which has been evolving in isolation for millions of years. We can use this place as a natural laboratory to understand evolution - just many different aspects of evolution can be understood here by various studies. And, these organisms have been here for millions and millions of years and it's my attitude that they should be allowed to remain here. There's always that argument that people say that who knows what we will find in this biodiversity that's being lost - maybe someday we'll find a cure for cancer in one of these fish. Maybe - I don't know. But if we lose them we never will know. (48:17)

JB - And in the time that you've been coming here, it's gotten a lot more popular (DH - right). People are starting to come in large numbers?

48:27 DH - Yeah, tourism is definitely picking up. There was a National Geographic article - we started noting quite a bit more tourism then. European tourism picked up. There's a lot more local tourism - a lot more Mexicans coming here much more than they used to. At times of the year, Semana Santa - during Easter week - this place is just wall-to-wall people, practically. Not this poza so much but other, more accessible ones. Tourism is going to have its impact, there's no doubt about it, but at least now the reserve has been established and there's a management plan in place and tourism will be controlled and the really critical habitats will be protected. (49:01)

JB - But isn't that in some ways a good thing because (DH - Certainly, yeah) because when people know about it they'll care about it

49:09 DH - Yeah, there's no doubt about that. And obviously there are certain conflicts between¿management of the reserve and the people who've been living here for hundreds of years. Basically, people were making a living in this basin and the way in which they make their living might be affected by the reserve management. And so tourism could offer a very distinct alternative to them. If people start coming here there will be another resource there to support people. (49:38)

JB - Do you have misgivings about us describing the natural beauty of this place? That too many people may say, "let's go down and visit CC?"

49:48 DH - (chuckles) I do little bit. That first - that occurred to me when I was first approached about this. But in the long run it's going to happen and to me the only way to save this place is through public education and the tourism will increase just through word of mouth if nothing else. And so to me it's better to talk about the real values of this place and educate people to that, so when they come here they're really understanding of it and they act appropriately. If they don't know, they'll be much more prone to trash the place. So, public education to me is really the key. Tourism will happen, we might as well face that and try to educate the public to the resources that we have here.(50:26)
50:40 JB - So, let's talk a little more about the pressures on the water supply here. This is not the breadbasket of Mexico but it's an important area for cattle feed production, right (DH - right). How do you balance those things - the age-old question of conservation - the springs versus the very legitimate need (DH - yeah) to produce feed for cattle to produce food for the country.

51:19 DH - it's a real rough one. It basically boils down to an economic issue. I mean, people are basically making money raising alfalfa in the middle of the desert and that groundwater pumping that occurs to raise that alfalfa is clearly going to impact places like that. And it really boils down to making economic decisions and unfortunately it's very difficult to put an economic value on these endemic species and just the aesthetics of this sort of place. So I think that's kind of key - people have to step back and start putting real dollar figures on the value of these sorts of resources or the next thing you know they're going to be gone and someday we're going to wish we had them back. But it is very difficult to do that. (52:03)

JB -¿ Do scientists not understand the hydrology of why the water table is dropping and where the pumping is going on and all that?

52:16 DH - Right, we certainly don't know with any detail exactly where the water is coming from and exactly how this system works hydrologically. I think there's a consensus that the absolute highest priority for research for this basin is to try to figure out where the water's coming from and how to keep it coming here. The fear is that some of this agriculture going in and surrounding the basins is tapping the recharge to this valley. And that if they take the water out of the groundwater there and irrigate alfalfa with it it won't be arriving to these pozas. But the bottom line is we just don't know where this water's coming from so clearly we have to understand where the water's coming from before we can deal with the management issue of how to control usage and assure that the water's always getting to the pozas. (53:02)

JB - There's a pretty strong feeling by people who've studied CC that the pumping for agricultural use is directly affecting the level of the pozas.

53:22 DH - I think talking about the pozas specifically there's not much data that really indicates that the groundwater pumping is affecting the pozas. I think that what has affected the pozas so far has been all of the canal digging which went on over the last century and has clearly extracted lots and lots of water from the basin, taking it outside of the basin, and very slowly drained this huge sponge that this valley used to be. So that it took many many decades to do that but these canals, once dug, became new low points in the system. The water kept flowing in and eventually the big sponge was just dried up. So we see that the higher parts of the basin are now dry. But these pozas, for example - this is deep water that is coming up - this is deep water that has been underground for a long long time. It's perfectly conceivable that that aquifer could be being impacted by groundwater pumping elsewhere and the impacts really won't be felt here for decades or maybe even centuries. So I think it's critical to take that long-term view and do detailed hydrologic studies to try to figure out where the water's coming from. But so far I think the bulk of the impacts have been due to the canal digging and the slow draining of this sponge that was here just filled with water. This valley - it's interesting to look back at some of the early accounts - there aren't too many but for example there was a novel written by a gringo who came here¿He visited CC and spent at least several months here just as a tourist and it was interesting to see him comment that the train going through CC always stopped so that people could go duck hunting from the train. And of you were to take a train ride along the tracks around here now you'd always be very far from water. There's just no way you could ever imagine there being ducks out there. So, just that simple little statement made it clear that there was an awful lot more water here. Now, our studies are backing that up - there clearly was much more water here¿lots lots more (55:36)

JB - but to understand the overall direction things are going - has it been a success story - Mexico's designation of CC as a protected are?

55:59 DH - Oh, there's no doubt that the designation of this as a protected area is a success story. This is a very active reserve now. It's getting support from all different sorts of orgs - not just the gov't but the World Bank, the World Wildlife Fund - all sorts of different ngo's are supporting conservation efforts here. The reserve staff is growing very quickly, there's a management plan written and being worked on now. The infrastructure is in place to properly manage this place. We're setting priorities and trying to figure out how to go about doing it. We lack a lot of information but the plan is there, the information hopefully will be gained and this place will be properly managed in the near future. So I think it's very definitely a success story - I'm very optimistic. There are some major questions like this issue of where does the water come from. But at least now there's lots of support towards finding the answers that we need. (56:58)

JB - And what kind of abuses of the land and the water that the protected status will hopefully prevent?

57:11 DH - Hopefully the protected status will prevent over-exploitation of water, which would certainly impact this place. There're other things - tourism, if we didn't control it in some ways, would clearly have its impact - you'd have people jumping into these fragile pools and trashing them pretty quickly¿ We can certainly set aside areas where people can come and enjoy it and we can control access to other areas¿where people can look down in and see¿the natural ecosystem functioning as it really should. So tourism can certainly have its impacts. Grazing is an issue which I think will have to be dealt with in the future. There is quite a bit of grazing here - you see a lot of horses out in the valley. It's not clear exactly what impacts its having b/c it just hasn't been studied yet. Some of the big threats here, however, include invasions of exotic plants. One that I'm particularly concerned about which has just popped up and is just starting to get some attention is salt cedar, tamarisk, which is a major impact on southwestern US deserts. Millions and millions of dollars go into control of salt cedar in places like New Mexico, Arizona, California. It's had severe impacts - it uses a lot of water¿it will drop water levels very quickly¿changing flows¿which will quickly affect fish populations. And it has established here - we've seen it as established in some of these recently-dried pozas where you get newly exposed soils¿Its seeds are dispersed by winds¿Also ¿seen in areas heavily impacted by horse grazing¿In these disturbed areas it's clearly establishing and it's not going to be easily removed¿If not addressed soon, it could become a very big issue, costing millions of dollars in control programs to try to get rid of. (59:40)

JB - I wanted to put the¿76-year protection in the context of Mexico¿ I don't want to exaggerate¿because places needs work¿I want your honest opinion¿Is this indicative of a trend in the country - that they are getting more proactive, more conscientious about areas like this that need immediate attention. Is this beginning to happen more over time?¿

1:00:35 DH - Oh yes, certainly. I think there's not doubt that conservation awareness in Mexico is increasing very quickly. They're doing an excellent job with public education and people now are much more aware of the great biodiversity that Mexico ahs and its value and there's no doubt that much more attention is being paid to management of these communities that are endangered otherwise. So I think from a national perspective yes, there definitely is much more interest in conservation than there was, say, just ten¿ or twenty years ago.

JB - Is this one of the better examples of that? Could they have done more here?

1:01:20 DH - No, I really don't think they could have done more here. I think there is much more to be done but I think they've done as much as they can given the situation. Realize, of course, that¿parks in Mexico are often very different than they are in the U.S. This park is mostly privately owned or it's owned by ejidos¿and the park is then imposed on top of those private land owners..making management very difficult b/c all of those private landowners have their own idea of what they want to do with their land but then this reserve is imposed and they have to at least discuss the management of their property with the reserve and get approval from the reserve to do whatever they want. And you can imagine trying to run a reserve with 50 or 100 different individual landowners¿So, given that background, I think they've done an incredible job of bringing people together here and they've gotten great support for the most part from the local landowners. And the local landowners have often had to change their way of life to a significant degree which wasn't easy for them at first. But I think the reserve staff has done an excellent job of reaching compromises and being aware of the needs of the local people, addressing them, and still trying to accomplish reasonable conservation goals. (1:02:42)

JB - But there was opposition¿

DH - 1:02:48 And there always will be opposition. Everybody's going to have different ideas about how the land should be managed¿ For example, when the gypsum extraction was closed on the dunes, the mayor's office was occupied for a couple of weeks and there was a big outcry. That was 90 jobs that were lost due to the declaration of the reserve and the closing of the extraction¿(1:03:14)

JB - Was there any organized opposition to the creation of this protected area as regards the ponds.

1:03:23 DH - Truthfully¿I don't remember much organized opposition. I think there was always talk but the reserve was declared before the opposition really got organized¿ But then there was that one fairly major encounter when they closed the dunes. And there's just always been a lot of discussion too - not everybody agrees with exactly how the reserve has been managed so far. Some of the impacts that are often discussed are fishing - people used to fish here quite a lot. I don't know - we don't have the data to say that that fishing was having measurably impacts¿I rather doubt that it was, but one of the first things they did was they said you can't fish here anymore. But lots of people ate lots of fish here and weren't very happy with that decision, and there's always been quite a bit of illegal fishing since then. I'm sure that fishing could have its impacts and it certainly need to be controlled but perhaps¿we could open fishing back up on a limited basis. (1:04:35)

JB - I haven't seen any fish of any size worth eating yet.

1:04:38 DH - They're here, yeah. There's - the biggest mojaders people eat fairly small ones¿People always tell me that the CC cyclid is the best eating fish in the world¿ I always wished I could try it (laughter)¿(chat w/ JB)¿Actually, we do go to seafood restaurants in town but most they're serving ¿ another African cyclid¿There are others, too - people used to fish for catfish here¿ bass - there's a native bass here¿so, a number of species that people have eaten for years. (1:06:04)

JB - Well, you've done a great job telling us about the science and the ecology issues, what about just some stories that have happened to you and your students through the years¿Good anecdotes

1:06:30¿ DH - Standing here in all this sediment one comes to mind¿ One of my ichthyology students came on a field trip here a number of years ago and I'd noticed that she was not prone to getting in the water¿for whatever reason¿but kicked in and did her part¿One day she was fishing¿and I think she got snagged or something and leaned out a little bit too far and ¿ the next thing she knew she was waist-deep in all these snail feces and just screaming "Help! Help!" and everybody just kind of laughed at her. [not a funny story]¿ Some of my favorite recollections are¿campfires¿Dr. Minkley¿I came on many many trips w/ him. He always camped at a cave¿now sort of officially known as Minkely's cave¿[boring story about fond recollections around the campfire]. 1:08:14 There's always the UFO story - We were out¿by where you guys will be tonight - I had an ichthyology class camped out there and it was just starting to get dark and all of a sudden one of the students goes, "Woah, what is that" and there was a shooting star..way slower than any shooting star I'd ever seen and way way brighter¿and it was visible for 15 - 20 seconds¿18 to 20 of us saw it and then it just sort of disappeared by Sierra San Marcos and we always wondered what exactly it was¿ 1:09:01

JB & DH - discuss Zona de Silencio, a place famous for its UFO stories¿errant US missile launch¿big cover-up¿military came down¿extracted¿missile¿very quickly. Remote desert region¿impressive silence.

1:10:11 JG - I think the concept of old water is really interesting - the fact that this water is coming up from¿deep in the earth¿The concept of a spring¿if you could just emphasize¿that it really never rains here but there's constant water¿and what it looks like.

1:10:48 - DH - We're in the middle of the desert and the rainfall here is on the order of about five inches per year. It comes mostly in June¿but it rarely rarely rains here¿But if you look at these mountains during a rainstorm, you never see water flowing off them - this is a limestone area¿the water basically gets into the groundwater almost immediately. Any runoff you get off the rocks and the mountains finds its way into the ground in very short order. And it finds its way through all the boulders and the rocks eventually into cracks that connect up to faults. And the water apparently drops down¿to great depths. You get rainwater, it's basically acidic so it dissolves limestone so you get cavern formation very quickly. And over millions of years you get huge underground caverns which, in this case, are probably mostly filled with water below the water table that we're sitting at right now. And it then, for whatever reason you can get sort of an impervious layer that sits on top of that water and water will back up into the mountains building a hydrologic head so that any break in that impervious layer will - water will just flow up to the surface through that. And that's what these springs are - these springs are coming up along faults which are allowing water to find an escape and flow up to the surface¿So, a hydrologic head has built up¿(1:12:46)

1:12:53 DH - There are actually sort of two kinds of springs here. There are the ones which are recharged from the local adjacent mountains and sort of a shallow, non-thermal aquifer¿historic wetlands very near the edge of the mountains and I think there's a shallow aquifer that comes off the mountains and then is brought back up to the surface by clay layers or something. And that's the aquifer that's probably been most impacted aquifer by the ditching¿ And then there's this deep aquifer water that has found its way into the deep groundwater - probably big water-filled cavern systems deep underground far enough down that it's heated up by geologic heat and it eventually finds its way to the surface and that water¿we don't know, but it's very likely it spent centuries if not even thousands of years underground (1:14:01)

JG - So the water that's coming up in here could be thousands of years old.

1:14:18 DH - Certainly, yeah. I think that's one thing we have to conduct surveys to determine very soon b/c if it is, for example, thousands of years old, the impacts of pumping wouldn't turn up, perhaps for thousands of years, even. It's conceivable that the groundwater pumping going on now will not be reflected in outflow these springs for centuries. If it's taking that long for this groundwater to make it from rainfall in the mountains to the spring outlets it could be that one day these places are going to start drying up due to the pumping that occurred years and years and years ago. We need to understand that soon so we can predict that and manage the place accordingly (1:15:08)

JB & DH - talking about fresh / salt water ichthyologists. Asks if having this as a lab is like a Disneyland

1:15:40 DH - It's just the diversity again, I guess is what it is, and the endemism. You have all of these things which have evolved in isolation, here¿So basically everything you're studying is a unique species¿And you've got a relatively diverse fauna¿And that's what really interests us. (1:16:16)

JB - Do you like to get in the water to get out of the heat. DH - talk about sun & shade. Until 1:17:02)

JB - Have you had many student or other researchers who've gotten heat stroke?

1:17:08 DH - Oh, certainly, nothing really critical¿but it's a very easy place¿especially people out snorkeling seem to forget about drinking¿so we do definitely have dehydration problems out here but we're real cautious (1:17:44)

JB - And again, what's going on in these cages over there?

1:17:47 DH - These cages ¿are experiments designed to look at the interactions between the fishes and the endemic snails. We have the polymorphic cyclid here, one morph of which feeds on the snails¿it has these heavy pharyngeal teeth down in its throat and the associated musculature which allow it to crush these snail shells and utilize the snails. The other morph can not do that - it has rather weak pharyngeal jaws, very delicate fine, long, pointed pharyngeal teeth and it can't break the snails so it can't derive any nutritional value from the snails. And so these cages manipulate the density of snails and fishes in an attempt to try to understand the interaction btw. the snail community and the fish community. Do the fishes, in other words, really control snail densities¿where the snails hang out¿(1:18:42)

1:18:45 DH - We've done a number of other experiments looking at interaction btw. the exotic species an the native species¿And there's also an exotic snail here¿We've been pleased to see that it's not dispersing quite as fast as we guessed it might. It has a reputation for invading new systems very quickly¿it doesn't seem to have made great inroads in CC¿I think that may be due to the very intact native fauna we have here which basically has the food web pretty well sewn up¿We've noticed the same thing with tilapia, the farm fish that was introduced here for food production¿ It's been introduced throughout this region and everywhere else practically it's invaded river systems very quickly¿It's been in CC for well over a decade¿but they just never have really taken off and become abundant, and I think it's due to interactions with the other species here. This community is intact enough¿that just don't let it invade. ¿ All cyclids have a lot of parental care¿it could be that this cyclid is tough enough - it's managing to eat the¿baby tilapia. (1:20:38)

JB - Of all of the kinds of ornamental aquarium fish, someone tossed another couple in here.

1:20:58 DH - We certainly see other spring systems¿Florida has every exotic species that's ever been in the aquarium trade, practically. Nevada has lots of beautiful little desert springs which have nothing but exotic species in them now¿California deserts the same way.

JB - This is kind of a common problem¿People feel compelled to dump aquarium fish in natural springs.

1:21:35 DH - Seems that way¿It's a very common problem¿It's either fishes that are introduced for sport fishing purposes, or food production¿or it's these aquarium fishes¿they're thinking they can introduce them into these places, and come back years later, harvest them, and sell them back to the fish trade¿ Typically, the fish trade..resists buying wild fishes for a variety of reasons, both ethical but also practical in that they never can tell what parasites or diseases they're likely to bring in from these wild populations. (1:22:23)

1:22:24 JB - As far as you know, there are no CC African jeweled cyclids in Monterrey pet stores. DH - Probably not¿I think, especially at the wholesale level, jewel cyclids are easily reproduced in aquaria. I'm sure there are lots of people producing them¿and at the wholesale level they would not be very valuable¿Very easy to harvest¿We do know now that if we wanted to¿we could control population levels by trapping¿they're a trap-happy species¿With enough effort¿we could go out¿and trap hemichromus and keep their populations at bay. 1:23:33

DH says again that it looks like humans have been moving them around. JG - 1:24:08 - Is it possible their eggs can stick to a human?¿ DH - Conceivable¿We worry more¿about this exotic snail¿than the exotic fishes¿once you've got them in your aquarium they're virtually impossible to get rid of. You get them in your gravel and you can even clorox your aquarium and they just shut up¿They can live through a long treatment of chlorine¿About the only way to get rid of them is to boil your gravel¿The little ones¿can easily get into tennis shoes¿So we're trying to pay a lot of attention to drying our equipment¿ They haven't invaded as quickly as we've guessed¿We guessed they would have impacts on the native snail¿There are no good older data so we can't really tell¿We do have some experiments which will hopefully shed some light on the possibility¿ 1:26:00

1:26:40 - 28:28 ambi - water flowing, reeds 1:27:32 - reeds louder until 28:02

1:29:05- 30:02 ambi - swimming, walking, rustling, splashing

1:32:30 ambi - off-mic talking btw. DH & JB, but lots of SC noise.

1:33:06 - 33:38 ambi - off-mic talking and swimming and water flowing, wind

1:37:57 SC - this is the little canal

1:38:00 - 40:08 ambi - water flowing¿really neat. Wind towards the end so SF moves.

1:40:30 - 43:00 ambi - more water flowing, a little louder this time.

1:44:45 - 45:30 DH - unusual to hear sounds of gurgling water in CC, gradients aren't usually that much but here we have an unnatural situation. Canal constructed a number of hears ago¿drains¿and diverts water¿but now it's canalized into this canal and drops into this spring pool¿water mining by digging small canals connecting up into bigger ones and little by little draining all of these shallow marshlands. 1:45:48 ¿A lot of this could be recovered fairly quickly¿one could go about filling these small canals relatively easily and inexpensively¿1:46:11

JB - Clarity of water amazing¿like Carribean¿

1:46:30 DH - ¿ can see nuances between gradients¿:43 I think the water transparency is due to two things - the spring boils - the water is coming up from very deep and there is no real sediment source down there¿:58 And then once on the surface you get the photosynthetic action¿any turbidity¿gets tied up and then settles out relatively quickly¿

JB - Is this water even clearer than really clear salt water?

1:47:35 DH - I'm sure you could compare it if you did the right analyses¿I'm sure it probably is¿have plankton in salt water¿

JB - is this the clearest water you've ever been in?

1:48:09 DH ¿Right up there¿Yeah, I think it probably is¿:25 It's incredible visibility. That's another big attraction of this place - you can do all sorts of observational work here that you can't do in other fresh water habitats. It's not that often that you get such incredible clarity in fresh-water habitats (1:48:45)

JB & DH chatting¿

1:50:30 ambi - (some ambi before but can hear car doors slamming)
1:50:57 - 1:51:15 ambi - with wind, good

1:51:50 - 54:00 ambi - swimming with periodic blowing through the snorkel

1:54:20 - 25 ambi - breathing / blow

1:55:14 - 16 ambi - one blow from the snorkel

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