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Mexico 2009 - Oaxaca, Chiapas, Veracruz

Some brief insights into the Mexican ichthyofauna

Sierra de Juárez, Oaxaca

The first stage was a kind of cold temperate fog forest located in the very heart of the Oaxaca state, the Sierra de Juárez. It’s on the way south between Oaxaca city and Salina Cruz. If you are heading westwards you are crossing an Atlantic-Pacific watershed. The mountain range reaches 2750 m in high stretching from NW to SE. On the NE slope of the mountain range there are plenty of tributaries to the Rio Coatzacoalcos running all the way up to the Caribbean Sea, on the opposite SW slope there is the Rio Tehuantepec basin. The latter empties into the Gulf of Tehuantepec (Pacific). 

Moses and ferns are thriving in this moist environment. They are growing virtually everywhere, here on vertical rough rocks. Almost any surface is covered by them.

Heimes (2010) provides an excellent overview about tree frogs of the genus Charadrahyla from Mexico. Some members of this genus inhabite the Oaxaca fog forest. 

Water is flowing everywhere in Oaxaca Fog Forest. Small streams coming up from the rocky bottom flowing along the road sinking into the soil, later accumulating to rivers or just evaporating anywhere. There plenty of wild rivers running through the forest. I fished in more than six location. I did not catch any fish although some locations are really smelling like Priapella. Probably my equipment did not meet the unique conditions of hill streams. 

Massive clouds of fog are caught in the Sierra de Juárez canyon. It was permanently raining perpetuating the moist environment. The speed of fog clouds moving was impressive. It took only seconds from a cloudy view to an excellent far sight view. 

Leaving the road MEX190 I was trying to pass the Sierra de Juárez mountain range between Zacatepec and Maria Lombardo de Caso on the MEX147. Due to the extreme bad road conditions after Zacatepec, constant rainfall and the lack of 4WD I gave up after wasting four hours. I returned to the road MEX190 heading southern towards Salina Cruz.

The first poecilid I caught: Poeciliopsis gracilis, male, Bartolo location

The corresponding female of Poeciliopsis gracilis, Bartolo location

Heterandria bimaculata was ubiquitous; at virtually any location I found this species. Picture shows a male.

An Anura tadpole of a yet undetermined species.

This biotope is located half way from the major highway to the Pacific coastline. It’s a small stream which contributes to a system which finally empties into the Pacific. 

Partially dense canopy coverage and the slow water movement mediates a layer of leaf litter accumulated on the sandy-muddy bottom. 

Livebearing Poecilia and the tetras Astyanax were rather frequent.

Astyanax aeneus E-MEX 02-09, probably the most frequent tetra in Mexico, usually iving a small shoals of up to 10 individuals; formerly misidentified as A. mexicanus.

The landscape around biotope E-MEX 02-09 was arid and of a savanna type. Fields are used as cattle pasture.

Poecilia sphenops E-MEX 02-09. Picture shows a young female. Also a very common species in southern Mexico.

Biotope E-MEX 03-09 at El Fortin is the only brackish water habitat I went to on this trip. The deeply greenish turbid water features rich biodiversity.

Mangroves are a typical vegetation form in tropical to subtropical brackish water environments. 

A single individual of Anableps dowei Gill, 1861. Watch the horizontally divided eyes after which the fishes are named. Anableps possesses a mattress-shaped swim bladder giving them enormous floating. They are using the enormous floating when grazing algae; the fish snaps thick algae thriving on the submerged mangrove roots. Now they are using shift lateral head movements and additionally the floating body to tear the algae off the roots.   

Without a doubt the most beautiful Four-Eye is Anableps dowei Gill, 1861 inhabiting brackish water habitats along the Pacific coastline of Central America. Their are living in shoals grazing on algae which they tear off the roots of mangroves. They shoal swims deep into the mangroves at high tide to conquer new feeding places. When the water retreats at low tide the shoal is following the retreating water level returning into the main channel. The pic shows a small shoal in the main channel at low tide. 

A beautiful livebearer living in the nutrient rich, warm water: Poecilia butleri Jordan, 1889. Thanks to Harro Hieronimus/DGLZ and Michi Tobler for identification.

Read more about this eye-catching species here. 

The predatory gobiid Dormitator maculatus (Bloch, 1792) is common in southern Mexico.

The first cichlid: Cichlasoma trimaculatum (Günther, 1867) was caught by a local fishermen. 

The rather speciose biotope attracts plenty of piscivorous hunters. Several Snowy Egrets, Egretta thula, family Ardeidae, were hunting along the mangroves.

Another piscivorous bird is the Neotropic Cormorant (Phalacrocorax brasilianus, family Phalacrocoracidae.

The Little Blue Heron, Egretta caerulea, family Ardeidae was also among the avifauna of the El Fortin brack water channel. They were by far not as numerous as the snowy egret. 

I am greatly indebted to Mr. Rüdiger W. Riesch for identifying birds species of my Mexico trip. 

One of the birds living in this arid and hot vegetation is steadily tail whippingTyrannus melancholicus, the Tropical Kingbird. This bird can be frequently encountered. 

Typical tree as an attribute of the landscape when heading back northwards. Among the trees and bushes bird life was abundant.

I arrived in San Cristobal de las Casas late in the night. I took some pictures and spent the night there. There are plenty of well preserved buildings featuring colonial style architecture in San Cristobal de las Casas. This place is worth goirng there even you are not too deep into architecture and colonialism. 

This is the largest specimen of Astyanax mexicanus. It is a mature female with 89 mm SL. 

The bottom was partially covered by snail housings.

Biotope E-MEX 05-09 at Sushila is located on the way towards Laguna Miramar. It’s a swordtail habitat. I caught wild Xiphophorus for the first time in my life.

The water was slightly turbid, the bottom covered by leaf litter. At the time of my presence the weather was sunny alternating cloudy with some rain drops.

Beautiful blueish wild swordtails Xiphophorus hellerii; a mature male.

The lion share of the swordtails were covered by melasoms; small spots all over the body and fins.

There were plenty of Procambarus (coded CR29) among the leaf litter at the bottom. Some hauls brought up to 4 specimens.

Experts were unable to guess the identity of this species based on a seires of the displayed specimen.

Two years later, during my Mexico 2011 excursion I was returning to this place and caught crayfishes readily identifiable as Procambarus llamasi Villalobos, 1954. This species is characterized by fine, densely arranged chelate setae and a distinct white or yellow horizontal band on the exoskeleton. P. llamasi is growing rather big. Hence, the pictured individuum seems to be a juvenile not yet showing the species’ characteristica.

Biotope E-MEX 06-09 located ca. 2 km before Patihuitz headings east had wonderful riparian primary forest. Water was extremely clear.

Aside the road MEX 307 from La Trinitaria towards Lagunas de Montebello there is highland pool which possesses an interesting aquafauna. 

Xiphophorus hellerii; a mature female.

Leaf litter and drift wood on the bottom. The swordtails I found here seem to be the same form as in the previous biotope.

Poecilia sphenops from Santa Rita; mature male.

An interesting and rare species caught here is Profundulus labialis. Picture shows a juvenile.

Poeciliopsis hnilickai from Santa Rita; mature male. They were rather abundant in this biotope.

Poeciliopsis hnilickai, mature female.

The crayfish Procambarus acanthophorus dwelling on the leaf litter covered bottom.

Thanks to Chris Lukhaup for identification of this species.

Thanks to Michi Tobler for identification of this species.

Thanks to Michi Tobler for identification of this species.

The National Park around the Lagunas de Montebello featuring residual primary rain forest. You can stroll through the forest on some paths or take a refreshing bath in one of the Lagunas.

The Laguna de Tziscao belonging to the Lagunas de Montebello. Unfortunately the weather was bad. Hence, the pictures are not as brillant as they should be.

When traveling in Chiapas province, southern Mexico you will certainly encounter some collapsed road, like the highway MEX 175 Lagunas de Montebello towards Ixcan (towards east).

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