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[sergeyal]

Hello
My name is Sergey ,I'm from Israel.
I want to thank Ivan Mikolji for his high quality  film.
I really enjoyed to see  Venezuelan underwater habitats and their surroundings  .
I think every one who particularly interested in South American fish or in Amazon rivers  in general must see this documentary.

Following this movie i want to ask Ivan some questions about my favorite species :

what are the feeding habits of potamotrygons  ?
are they pure predators or opportunistic like many other species.
same question about pt.Altum

in which river system potamotrygon yepezi ( http://www.youtube.com/user/fishfromvenezuela#p/u/64/sQPmsmIDYLA ) occurs ?
is it true that this specie endemic to Venezuela?

is there any differences (in feeding habits ,aquatic environment or something else) between potamotrygon and plesoitrygon species (antenna rays).
in your opinion why antenna rays have such huge tails (like marine rays and unlike potamotrygon)?


Thanks.

[admin]

Hi Sergey,

Thanks for the good word on the documentary. I'm happy to hear that you enjoyed it.

For what I have seen in the wild, they feed during the day and during the night.

During the day, freshwater rays move slowly around the river bottom stirring the sand, probably looking for invertebrates or small catfish which bury themselves in the sand. During the night, river stingrays move faster and we have always found them going after fish towards the river bank or shore. They swim from the deep towards the shallower areas and kind of swim on the water surface until the river gets so shallow that any sleeping fish that was in the area winds up under its body. Freshwater stingrays are opportunistic feeders during the day and excellent predators by night.

I have never had the chance to see altum by day in their natural habitat in the 5 long years that I have been snorkeling the rivers. Sometimes when I watch a video of altum in their natural habitat by day posted by people on youtube I think to myself… “They are very, very, very lucky or they caught them by night and released them in front of the camera by day”. So… I have no idea of what they eat, I could only speculate. My best guess is that they eat small shrimps, fish fry, insects that fall in the water and maybe perifiton.

yepezi is from the lake of Maracaibo and up till now I think it is an endemic species from Venezuela. I’m not entirely sure because in the Maracaibo lake we have found 2 species of rays, yepezi and magdalenae, the second having the name of a Colombian river. So if we have a Colombian ray, probably Colombia could have yepezi.

The last question got me out of base. You need someone who is an expert on the Myliobatiformes order, not a self-taught person like me. I’m not a biologist or ichthyologists; I’m more of an explorer.

I hope that I could help you in some way and thank you very much for joining the forum!

Ivan Mikolji

[sergeyal]

Thanks Ivan.
freshwater stingrays are pretty common in the hobby , but there is lack of knowledge about their behavior in nature.
your information is very valuable.

They swim from the deep towards the shallower areas and kind of swim on the water surface until the river gets so shallow that any sleeping fish that was in the area winds up under its body. Freshwater stingrays are opportunistic feeders during the day and excellent predators by night.

Such a sophisticated  hunting technique typical for all kinds of fw rays ?

Have you noticed some signs of social behavior among young or mature fish?
Different species like paratrygon aireba ,plesiotrygon iwamae , potamotrygon shroederi and potamotrygon motoro can be found in same rivers ?

Is there any research on freshwater stingrays in Venezuela?