Rio Tehuantepec

[seanwelsh1]

I know that both Amphilophus trimaculatus and Paratheraps zonatus inhabit this river but do Astatheros macracanthus also live there ?

[Bas Pels]

Basically, macracantus and trimaculatus have a similar function - and therefore where you can find 1, the other will be missing

[seanwelsh1]

Ah ok i thought that i had heard in Juan Miguel presentation that both these fish lived in this area ?

What other species come from this area then ?

[michi tobler]

Basically, macracantus and trimaculatus have a similar function - and therefore where you can find 1, the other will be missing

Hi Bas,
that is actually not correct. We regularly collect the two species together (also along with Vieja and C. grammodes). The two species also have different trophic niches.
Cheers, m

[seanwelsh1]

Basically, macracantus and trimaculatus have a similar function - and therefore where you can find 1, the other will be missing

Hi Bas,
that is actually not correct. We regularly collect the two species together (also along with Vieja and C. grammodes). The two species also have different trophic niches.
Cheers, m

all in the Rio Tehuantpec system

[Bas Pels]

Basically, macracantus and trimaculatus have a similar function - and therefore where you can find 1, the other will be missing

Hi Bas,
that is actually not correct. We regularly collect the two species together (also along with Vieja and C. grammodes). The two species also have different trophic niches.
Cheers, m

Thank you for correcting me

[michi tobler]

all in the Rio Tehuantpec system

I have never fishes in the Tehuantepec proper, but A. macracanthus and C. trimac should occur there. Also, I'd expect Vieja zonata. C. grammodes and V. hartwegi probably not; they co-occur with the former two in the upper Grijalva, but probably not in the Tehuantepec.
Cheers, m

[Rico Morgenstern]

I find it interesting that Astatheros macracanthus und 'C.' trimaculatum are present in the Upper Grijalva drainage. Are these populations translocated from the pacific slope or could this be a natural occurence? Taylor & Miller (1980: http://hdl.handle.net/2027.42/57129) noted some similarities between the Upper Grijalva and Pacific coast ichthyofaunae, which would support the latter possibility. However, there's a serious objection: apparently these remarkable and readily identifiable cichlids have both never been recorded from there before.

[michi tobler]

Hi Rico,
excellent point! Actually you got me on the wrong foot, and for a moment I thought my memory was failing me. So I went back, checked my notes, and plotted the sites on a drainage map to make sure that they are part of the Grijalva. At three out of the four sites I recalled we collected trimac or macracanthus or both (at the fourth most eastern one it was only grammodes). As you can see on the map, all sites are part of the upper Grijalva and drain towards the Gulf of MX. Interestingly enough, I also found the following note in my field book: " Region is very flat. Could stream capture cause faunal exchange between Coatzocoalcos and Grijalva (or Pacific/Grijalva)?". Apparently we realized in the field that something was fishy, but I actually forgot until you mentioned it now. Clearly something I should follow up on. Juan, any comments?
Cheers, m

[seanwelsh1]

thanks michi,

I have following Amphilophus trimaculatus , Paratheraps zonatus and Astatheros macracanthus (all very small atm) in a 680L tank. I am trying to create a biotope with these guys . Have you any underwater pictures or descriptions of the river system please

[michi tobler]

As I said, I've never been to the Tehuantepec. But below some pictures from sites where we collected trimacs and macracanthus (they correspond to the sites on the map from west to east). I am sorry for the poor quality pictures, but I only had a point and shoot camera available on that trip. What you can see nicely on the pictures though is that all of the three rivers have sandy bottom with relatively little structure. Cichlids are pretty easy to catch here around undercut banks and snag. As usually, no macrophytes.Other fish we collected in the area were Profundulus, Poeciliopsis, Poecilia, Astyanax, Atherinella, Rhamdia, and Ophisternon. I hope that helps.
Cheers, m

[Rico Morgenstern]

Thank you, Michi, for the detailed information. If these are natural populations, it seems that they have colonized the Grijalva system only recently. Otherwise they would certainly be more widespread. Interesting in this context are records of A. macracanthus in the Motagua drainage and of 'C.' trimaculatum in Rio Malatengo (upper Coatzacoalcos system). The type locality of Cichlasoma tenue Meek, actually a synonym of 'C.' trimaculatum and not of 'C.' salvini, is also on the Atlantic side. However, in this case Miller (1976: "An Evaluation of Seth E. Meek's Contributions
to Mexican Ichthyology" Fieldiana [Zool.] 69, no. 1: 1-32) concluded, that the locality is wrong as a result of a mix-up. Interesting enough, the material from which he had drawn this conclusion includes also A. macracanthus.

Best regards
RM

[michi tobler]

Hi Rico,
the colonization must not necessarily have been recent (I guess it depends on the definition of the term). The upper Grijalva has a very unique fish fauna with numerous species with relatively restricted distribution. So, not being more widespread does not necessarily mean a recent origin, but it could also be indicative for particular environmental conditions. The fact that multiple "Pacific taxa" (the cichlids, but also some Poeciliopsis) made it into the upper Grijalva suggests to me that the area has been colonized naturally, maybe through stream capture, and not by human introductions. This may also apply to the Coatzocoalcos records. If you look at the tomography of the area, stream capture events do not seem far fetched in the area. It would really be interesting to tackle this in more details, but there are not too many collections from these areas. I'll talk to Allison Pease about this. She did her dissertation about the Grijalva drainage and she spent a lot of time catching fish in the upper Grijalva.
Cheers, Michi

[Willem Heijns]

Interesting topic. Still, I find it hard to believe that stream capture could be the explanation for Pacific species like macracanthus and trimaculatus occurring in the upper Grijalva. One reason is that there is a well developed mountain range between the Grijalva basin and the Pacific coast with peaks between 1,200 and 1,900 meters elevation. Secondly, why would Pacific species invade the Grijalva system and no Grijalva species cross to Pacific rivers? Taylor and Miller (1980) only noted similarities between Pacific and Grijalva species, which is quite different from finding the same species on both sides of the mountains. Any invasions into the Grijalva system could have occurred from the west though.

At the narrowest part of Tehuntepec stream capture could be possible. Species crossing the "borders" between Pacific slopes and the Coatzacoalcos drainage could very well have happened. In fact, we found trimaculatus in the Río Grande, a tributary of the Coatzacoalcos. Dispersal from there into the upper Grijalva seems much more difficult to me.

The Río Tehuantepec is further to the west. Finding grammodes there would be a very big surprise, raising some intrigueing questions.

[Bernard GBX]

Hi everybody,
it's a really interesting topic.
I found Trimac just near Tuxtla guttierrez (in 2007). So we can say that this fish is in both side of Mexico.
But if you agree with Rican, this species became to Amphilophine who invide North america 26 myear ago. And at that time, I dont think that the landscape was like today. I think too that tehuantepec could be under water and maybe north mexico was colder than today (so No cichlids on north).
Only 10 myear after is the arrival from Herichthyines with Vieja and lot of species from Usumacinta/Grijalva and the North atlantic mexico.
Trimac and macracanthus were not enough specialized to resist everywhere and the Herichthyines conquest was really great.
Just for the other question, we find Vieja guttulatus / zonatus on pacific slope, so there was too a population from North wich exists in South. But at this time the orogeny laramienne was ended and the landscape seems to be the same as today (even if the water level is not stabilized).
But it's only a theory !