Altum Fry in Nature

#1
Good Morning Everyone, I hope you're all having a good Memorial Day if you're in the USA or a nice Monday if you're in other countries.

My question is simple: Has anyone observed Altum fry in the wild? I'm wondering if any experienced aquarists that have visited the Amazon can elaborate on the environment best suited for raising Altum fry.

Re: Altum Fry in Nature

#2
Aha Lilhelper,

Well now you will find that you will get an animated response from Ed. Most of the Altum habitat is in the drainage of the Rio Orinoco and not in the Amazon, although our DNA analyses show that there are certainly altums in the upper drainages of the Rio Negro, which is then in the drainage of the Amazon. Ed grew up in the vicinity of the town of Puerto Ayacucho, Venezuela, hence his forum name! There he witnessed young altums in their natural habitat on many occassions and will be able to explain.

Kind regards,

Dirk
Somerset West, South Africa

Re: Altum Fry in Nature

#3
Hi Eric and Dirk.
Just to clarify, I was born in Maracaibo, Venezuela but a month and a half later my parents and I (oldest kid in my family) moved to Miami, Florida. I returned to Venezuela in the mid 70's (already well bitten by the aquarium hobby thanks to my grandmother). I studied 5 years focusing on Aquatic Biology but before graduating I started to work as a translator and interpreter for the oil industry in Venezuela. I lived in Puerto Ayacucho three years but visited their and adjacent Orinoco Basin since the late 70's until 2001, when my wife and son finally moved to Maracaibo, from Puerto Ayacucho. Throughout all these years I always continued collaborating with my ex-colleagues/co-students, to this day.
OK... enough of myself...just wanted for Eric to have a summary of my background in regards to the geographical area and species of our interest.
Most of my experiences in the Orinoco have been published here on the forum and I will try to post links to those old threads in which you will find some in depth answers to your interest on young altum and their habitat.
Among some of the more pinpointable things I can summarize for the moment are:
1. Breeding altums prefer to lay their egg cutch on vertical or diagonal wood or rock substrates, rather than leaves. In nature I have seen clutches protected by parents on a) woody roots jutting out from a stream bank (Upper Pozo Azul, North of Puerto Ayacucho), b) a submerged fallen tree trunk, in Pozo Cristal, just a few kilometers South or previous location, and c) on the "under belly" of a large partially submerged boulder, near the mouth of the Cataniapo (on Orinoco), also Puerto Ayacucho area.
The above describes the three moments that I can remember to have noticed parents guarding clutches. I could not get close enough to see if any fry had hatched, and actually only once could I distinguish there really was a clutch... the other two were by pure deduction and observation of the behavior of the parents from a safe distance so as not to disturb them.
Water was between pH 4 and 5 and I would put the T in water at around 80F... but here we have something interesting... the fish know how to pick locations with warmer currents or sources to help incubate their eggs. The boulders I mention in the Cataniapo (for example) get really hot when the sun hits them directly, and I'm pretty sure this heats dissipates throughout the surfaces helping egg incubation. Even in the stream in Pozo Azul which was in its major part covered by forest canopy (at least back then it was), the fish always managed to choose warmer parts or currents to lay their clutches. In these waters, direct sunlight and the forest canopy make a big difference in temperature, as well as the underwater riverbed... you can be standing in 5 feet of water and feel cold on your torso while your lower legs are warm, or viceversa.
2) As to the younger juveniles. they will look for some very shallow ditches that form near the streams (these ditches can be seen just off the road in the Pozo Cristal area) and vehicles pass very close to them (back then, early 80's to mid/late 90's), there were offroad trails that a vehicle would need to transit to get to Pozo Cristal. These ditches were the easiest place to catch altum juvies. They were loaded with dead and dying vegetation, tetras and dwarf cichlids, and had plentiful invertebrate life. Average depth was around 2 feet, usually less. The water in the ditches was very warm and pH could be below 4.0. These ditches flow directly into the streams that end in the Orinoco or other major Orinoco tributaries.
Note that these ditches are dry a good part of the year and covered by grass, but when the wet season starts they fill up and the acid water starts to kill off the vegetation.
Hope this helps you to get a better picture of the environment for the younger altums, nominally near 1 inch body size.
God listens. He may not always give you everything you want, when you want it; but he always gives you what you really need, when you need it most!
E.R.

Re: Altum Fry in Nature

#4
What wonderful observations, Ed. Thank you for the animated response. :) I suppose these animals are pretty hardy in their natural habitat due to their proximity to roadways.

My fish are well past juvenile stage and are approaching their adult form. I reckon the fish are close to 1 3/4 years old as I got them at about 1". They are now about 2" - 2.5" of the Rio Inirida form.

Re: Altum Fry in Nature

#6
Lilhelper wrote:What wonderful observations, Ed. Thank you for the animated response. :) I suppose these animals are pretty hardy in their natural habitat due to their proximity to roadways.

My fish are well past juvenile stage and are approaching their adult form. I reckon the fish are close to 1 3/4 years old as I got them at about 1". They are now about 2" - 2.5" of the Rio Inirida form.
Long way still from their adult size which comes at 4.5-5+ inches SL (this is from tip of snout to the caudal peduncle AKA base of tail).

Really the fact that they can be found in streams near roadways has little to do with hardiness. The roads are in general, quite remote in an area of the country which, though slowly growing in population, it is slower still, in development, and continues to be basically rural, with minimal density of population. Even rural development is poor because the land is not apt for any significant agricultural development due to the acidity of the soil.

Ivan Mikolji has already reported the species disappearing from some Northern locations which are adjacent to the places I have mentioned (so also possibly they no longer exist in Pozo Azul and Pozo Cristal). This area is also where Horste Linke collected his first breeders (Laguna La Parhueña).

This said, the fish (altum) from this Norhernmost area of distribution could be hardier than those in the Atabapo and Ventuari where conditions are a lot more acid, and pristine... almost moonlike under the surface. The Orinoco from were it meets the Guaviare, changes considerably, from a black to amber and clear watered river to a browner, siltier and much more voluminous river, and then, when the Meta hits it (downstream of Puerto Ayacucho), it is much more similar to the Amazon.

And though the Inirida is also categorized as a blackwater river and it used to be so. I remember Heiko once explained to us that it has very much changed and is now a muddier river due to the mining activities (He visited there I believe in November 2009).

The thing is that the water where these fish live are so acid, that there are not many pathogens around to give them a hard time, and this of course, reflects in a very specialized immune system, which is not necessarily a good thing after these fish fall in our hands.
God listens. He may not always give you everything you want, when you want it; but he always gives you what you really need, when you need it most!
E.R.
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