Maschwitz, land of Cynolebias nigripinnis

By Pablo Calviño, SAA049
(translated by David Baker).

When we think about a locality of Cynolebias nigripinnis, the first place that comes to mind is "Maschwitz". This is not by chance. Comparing these cynolebias nigripinnis with those caught at other locations, historically, one could say that they were the first that were greatly admired and appreciated. Its appearance is quite something, somehow more complete than other nigripinnis, with multiple irridescent points seeming to be more turquoise and intense. In addition they have another attraction, as apparently to find Cynolebias "Maschwitz" lately is a challenge.

In the year 1998, after much searching, we could not find a single pair. The explanation may be that canals have been built on large part of the biotope. On the other hand, in the typical places where they are caught there has been more water than usual. These cynolebias could be victims of larger predatory fish since we have verified the presence of tarariras (Hoplias malabaricus) and Crenichiclas species, that have returned via the overflow of the larger bodies of water.

This year, we successfully made exciting trips to Argentina and Uruguay, where we obtained Cynolebias species that we had only seen in photographies, like the Cynolebias viarius, Cynolebias adloffi, Cynolebias gymnoventris and many others. But the collecting season was almost finished when we realized that we had left something pending. We needed to see if there would be any fish in the locality of the "Mashwitz Engineer". We asked ourselves, "Will there be Cynolebias "Machwitz" this year there?", and if so would the population be thriving or heading towards extinction, considering the increasing construction and exploitation of its lands.

The town is 45km from Buenos Aires, the capitol of Argentina. Like the killifish, the place has a special attraction too. These lands were acquired by Dr Don Benito Villanueva by the end of the 19th century, and on them he founded the Establecimiento de Campo "Los Arenales" (the "Sandy grounds"): this name indicates that in the past the sea bathed the zone, its sandy streets bearing testimony to this fact. The name was chosen at that time by the Argentine President, Don Figueroa Alcorta, in honour of the engineer, Carlos Maschwitz, who worked arduously on nuilding the Argentine Railroads and as "Ministro de Obras Publicas" (Minister of Public Works).

Today we can see houses constructed on these lands, ignoring the treasures buried beneath, built on stilts to ready for the flooding of the Río Luján. Additionally, this is one of the places preferred by aquarists for obtaining plants like the dense "Elodea", which abounds in the channels. It is interesting that we have never found a single Cynolebia in the same biotope as the Elodea. Logically, the elodeas are true aquatic plants, living permanently submerged and not tolerating drought. The Cynolebia are found in a different type of biotope of the region.

On the 1st October, it looked like an ideal spring day. We arrived at 12:30 under a cloudless sky, the temperature at 24°c and a slight breeze from the north east. Ideal conditions! We took the highway towards the "Dique Luján" (Luján Dock) and once passed the railway lines, we continued for about two kilometers. There, on the right, a road opens that leads to a small tributary of the river. On the right side of this, a channel runs parallel with the road for almost one kilometer, continually varying in width and depth, according to an official notice of the channel's cross-sectional form.

In the larger section of the channel, the depth of the water is 80cm and cleared of plants, but in smaller section of more than of 10m in length, the plants species Myriophyllum and Ludwigias were observed but not in abundance, where the water depth was between 10 and 30cm. Experience indicated that that was a suitable place to look for the Cynolebia. The ecosystem was so pleasant, small and delicate, that we decided to use hand nets to minimise the effect on the biotope.

Hidden there under the profuse roots, like we hoped, were our Cynolebias!

We found beautiful medium sized specimens of Cynolebias nigripinnis in relatively large quantities. With each Cynolebia that we caught, on average we fished out about ten tadpoles and the same amount of madrecitas (Phalloceros caudimaculatus).

The water was crystal clear and coloured a dark amber, pH 7.2 with a hardness of 10°dH, and a water temperature of 21°C.

Also we caught Cynolebias bellottii of approximately 4cm in length. These were found in greater quantities than the Cynolebias nigripinnis along with an abundance of snails in an extremely rich substrate. We named this location "Maschwitz, PC 99/11".

In conclusion, we can say that this location is one which takes longer to dry up, since its cycle extended until November (a couple of months but normal for the region).

As far as the adaptability of the pairs that we caught, it turned out to be optimal, especially if the aquarium enjoys a good substrate crowded with abundant myriophyllum plants of the same habitat. They did even better when moving them to a slightly more acidic water of pH 6.8.

Although the population of this biotope has increased with respect to the previous year, the climatologic variability and the increasing urbanization without concern for the ecological situation, puts the future of the Maschwitz biotopes in doubt.