Diamond tetras Moenkhausia pittieri in the wild | Mikolji

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Diamond tetras Moenkhausia pittieri in the wild

By Ivan Mikolji / 2009
 

When we think about freshwater fish that are in border of extinction what probably comes up to your mind is Panaque suttonorum commonly called the blue eyed pleco, Hypancistrus zebra or zebra pleco etc., but you would never think of Moenkhausia pittieri. Yes, Diamond tetras! Even though this small characiform is very prolific and can be bread quite easily in the aquarium hobby, it is disappearing in the wild.

 

Moenkhausia pittieri 101

Ornamental fish known as tetras belong to the Tetragonopterini tribe that includes genera as Astyanax, Briconamericus, Hyphesobrycon, Paracheirodon and Moenkhausia to name a few. This group is characterized by having an internal row of teeth from the premaxilla composed of 5 or more teeth on each side. The bone under the eye (big sub-orbital) having an area without scales and the absence of a ventral keel. The Moenkhausia genera can be distinguished by having strongly dented maxilla, disordered scales before the dorsal fin without forming a line (irregular pre-dorsal line), caudal fin lobes scaled at least in 25% and ctenoid type body scales which means that their scales have small spines on their surface which feel rough to the touch when stroked in a forward direction.

 

The Moenkhausia genera was named afterthe zoologist William J. Moenkhaus and the species name pittieri after the biologist Henri F. Pittier. The distinctive characters of the Moenkhausia pittieri species and what makes this fish unique is that its body is covered with golden iridescent scales. In the wild, their dorsal and anal fins show a violet coloration, yellowish caudal peduncle and its dorsal fin sometimes presents a white line.

 

 

Diamond Tetras are autochthonous to the Lake of Valencia basin. Actually, the “holotype” or original specimen used to describe the species by Carl H. Eigenmann in 1920 was caught in (type locality) the Tiquirito River, in El Cosejo, Aragua State, Venezuela which is one of many small streams that drain towards the Lake of Valencia. They are currently taxonomically classified as follows: Class: Actinopterygii (ray-finned fishes), Order: Characiformes (characins), Family: Characidae (characins), Subfamily: Incertae sedis

 

Location

The Lake of Valencia is located in an enormous valley or plain surrounded by mountains. The lake gets its waters from many little mountain streams. What makes this lake so special is that it has no outlet streams or rivers and it does not connect to any main river system or ocean. Its water levels are controlled by rainfall and evaporation.

 

The great majority of these small streams arround the Lake of Valencia have been contaminated with raw residential and agro industrial sewers which are mostly introduced without a previous water treatment into the streams or lake, making a biological unbalance which makes a direct impact on all the aquatic fauna and flora population.

 

 

First encounter

After looking for them for more than three years with no luck, a friend of mine called Simeon Perez told me that he knew of a place where there was a stable population in clear waters. After making me promise never to give the exact location out to anybody, he took me to his secret spot.

 

Simeon’s secret creek was the typical Moenkhausia pittieri mountain river habitat which are regularly clear watered and cold. It had a coarse gravel bed with abundant larger river rocks. In no place the water was more than 5 feet deep being 1 foot the average depth. The pH was 7.8 (slightly alkaline) with a temperature of 25 Celsius. (77 Fahrenheit). Simeon Perez told me that the alkalinity in the water was due to the large amounts of limestone rock which form part of the bottom substrate. The low temperature of the water is due to the amount of dense tall trees that grow on the creek banks letting practically no direct sunshine penetrate the water. In the dry season these small creeks stop flowing. The diamond tetras with all the other fish which inhabit the creek get caught in large puddles. The tall trees seem to be crucial for their existence for they keep these puddles from drying up for up to five to six months until the rainy season starts again. The trees also prevent the water from getting to warm for them to live in.

 

 

I found no submerged aquatic plants in the creek. The few species of aquatic plants that I found where the “partially submerged” type, which grow half in and half out of the water. In other aquatic biotopes, fish use aquatic plants as shelter from predators. Because of the lack of aquatic plants, the Moenkhausia pittieri dealt with this using the abundant drift wood and larger rocks as shelter but the most important factor in their survival in the wild is their quick acceleration response and high swimming speed.

 

Photographing this species underwater in its natural habitat was a real challenge. The 1 foot deep water had a strong current and the creek bed was full of awkward shaped rocks some protruding out of the water which made it almost impossible to lay flat. Even with a 10 pound lead belt I was still being dragged downstream. The water was so shallow that it was almost impossible to submerge my head straight. I had to take the pictures with my head submerged sideways, so I could look at the camera screen. Another challenge was the lack of light do to the abundant trees which blocked all direct sunlight making the camera take long in taking the picture. Added to this was another problem, the fish swam as fast as they could, fighting the current swimming upstream and passed by, with lightning speed, coming back downstream. Once I pressed the camera shutter button to take the picture, the diamond tetras where way gone or I was left with pictures of the end of their tails or a blurry picture. I wound up having to anticipate their movement and take a guess at shooting the pictures sometimes a second before. Added to all the situation was the usual hypothermia that always kicks in around 40 minutes after being submerged in the 25 degree Celsius water. The uncontrollable shivers make taking a good picture even harder.

 

 

The deeper areas of the creek or pools where much easier to lay still in because the current slowed down; but because of this, the creek bed was covered with a thick layer of silt. Once you entered a deep area and placed your foot on the bottom, a cloud of silt was created that left the small pool water murky and unusable for photographing for more than an hour.

 

In the 2 days of photographing, I took 870 pictures to wind up with a couple of decent shots.

 

Even though the pictures of the Moenkhausia pittieri mountain creek habitat are monochrome and monotonous and not as multicolored as other types of aquatic biotopes, they show what their true home looks like and these are probably the first underwater pictures to show it. As I know that good aquarium pictures of most fish can be found everywhere I try to emphasize on taking pictures of their habitat which are very hard to find and practically inexistent.

 

After snorkeling in the small creek for two days we spotted many other fish that share and coexist with them in the wild. It was amazing to me to see how sophisticated nature works in these small confined habitats and I’ll try to explain why as well as I can.

 

Two of the species of fish that inhabit their confined habitats are Hoplias malabaricus (wolf fish) and Crenicichla sp. AFF. geayi (pike cichlid). Now, if you place these two fish in any aquarium, it would be extremely hard for any tetra to survive and even less, thrive. These two fish are very voracious.

 

So, how does nature even things out? Well, there are large amounts of very prolific fish as, Poecilia reticulata (wild guppies) and many other small tetra species like Corynopoma riisei and many other tetras which I could not identify. These other tetras and guppies are easier pray for they are slower swimmers and smaller in size than the Moenkhausia pittieri which makes them easier to swallow or to be hunted by the predatory fish.

 

Other fish that we spotted and inhabit the creek with the diamond tetras are Corydoras aeneus and Ancistrus sp. (pleco). They are in charge of cleaning up after everybody’s mess.Aequidens pulcher, was one of the easy going cichlids that where always minding their own business and staying out of any trouble.

 

The adult male diamond tetras where much bigger in size than the adult females. The biggest males that we saw where around 5.5 cm. long. The adult males could be easily differentiated from the females by having the first rays of the dorsal, anal and pelvic fins elongated. The females where half that size. We also observed that they are a mid water dweller, only going to the surface if something that looked like food fell in the water. Their feeding patterns are basically opportunistic, capturing anything that that falls or moves on the water surface and that would fit in their mouths. Their feeding tendency is principally carnivorous being their most common prays, ants, termites, small moths, flies, mosquitoes and small wasps.

 

CONCLUSION

In many years of study around the Lake of Valencia rivers and creeks I have noticed that many fish are highly tolerant to contaminants. The highest tolerance can be found in Poecilia reticulata followed by Aequidens pulcher. The Moenkhausia pittieri are one of the extremely susceptible species which in my opinion can de used like a Canary in a mine. Once a body of water starts deteriorating, they seem to be the first ones to disappear.

A good green orientated idea would be to buy a plot of land where this small creek is born to preserve what could be one of the last natural habitats of this beautiful characiform. The diamond tetras of this creek could be used in the future to repopulate or reintroduce other recuperated rivers or creeks with an original Moenkhausia pittieri blood strain.

 

Hopefully, the diamond tetras will continue to exist in the wild but their future looks quite dim to me, so if you ever breed diamond tetras in your home aquarium always remember that there are practically non left in the wild.

 

Special thanks to Yoliana Añanguren from the UCV (Central University of Venezuela) for providing me with scientific species details of the Moenkhausia pittieri species.

 

This article has been published at:
• Tropical Fish Hobbyist Magazine - January 2010

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