Magdalena Loricariids

[Shane]

Some loricariids from the upper Magdalena near Giradot. I also finally managed to speak to a collector from the Magdalena about Panaque sp. "blue eyes." He said that they are still plentiful around Bucaramanga and a few other places, but that all the places where he knew he could find them were under either Guerrilla or Paramilitary control. Despite the best incentives Diego and I were willing to offer, he replied that no fish was worth his life. Given that this fish has been pretty much wiped out from the upper Magdalena, this inability to collect them might be good for helping the sp. rebound and recolonize its old habitats. Now on with the fish...

Since only one Lasiancistrus has been described from the area, Ithis must be L. caucanus.



An interesting Chaetostoma sp.



A very interesting Chaetostoma sp. Possibly C. leucomelas?



Another shot.



An interesting Sturisoma sp.



-Shane

[Plec0maniac]

very beautiful shane.. especially the chaetostoma, and the sturisoma looks like either a aureum or panamense

[Jools]

Since only one Lasiancistrus has been described from the area, Ithis must be L. caucanus.

Not an undescribed sp.?

Jools

[Jools]

very beautiful shane.. especially the chaetostoma, and the sturisoma looks like either a aureum or panamense

Sadly my catfish books are all packed away as I am about to move house but is it not more likely this fish is <I>S. festivum</I>?

Jools

[Plec0maniac]

its really hard to tell cuz sturisoma sp. really have little variations, except for the barbatum sp

[Jools]

its really hard to tell cuz sturisoma sp. really have little variations, except for the barbatum sp

Yes, but we know exactly where Shane collected these fish and so we don't just have to go external characterisitics.

Jools

[Silurus]

If we go by localities, shouldn't that be <i>S. aureum</i>, since the Rio Magdalena is the type locality of this species?

[Jools]

If we go by localities, shouldn't that be <i>S. aureum</i>, since the Rio Magdalena is the type locality of this species?

Seems likely and (from memory) fits the description in Hans and Ingos Catfish Vol. 1. book.

Jools

[Shane]

The Rio Magdalena has a very interesting fish population for a number of reasons. It is completely independent of any other South American river system and is seperated from all other river systems, especially along its upper course, by very high mountains. Leaving Bogota, you have to cross through a pass before you can start descending towards the Magdalena. The altitude at the pass, which is a LOW point in the mountains, is 8,900 feet (almost 3,000 meters)! These fish were caught at an altitude of 1,500 feet about 100 kilometers (60 miles) from Bogota. As you drive down to the Magdalena you descend almost 7,500 feet over 60 miles. It is an incredible drop! Many of the mountains that seperate the Magdalena system from the llanos system are snow covered for most of the year. This would make it highly unlikely that very many fish spp. could move, or be moved, between systems. This means that the Magdalena's fauna has been seperated from the rest of South America's fish populations since the Andes rose. It is also interesting to note that not all catfish groups are represented in the Magdalena. For example, Corydoras are absent and there is only one sp. of Doradidae. Interestingly, this population dynamic matches that of another secluded drainage, the Maracaibo Basin. The Maracaibo basin also lacks Corydoras. This would seem to point out that, even though now these two groups have diversified into hundreds of spp., they were probably rare before the Andes rose in the Cretaceous and Tertiary periods.
OK, so what is my ultimate point? Heok Hee was kind enough to provide me with a copy of Miles' "Peces Del Rio Magdalena" (1947). It seems to me that Miles went out of his way to try to identify the fishes he found in the Magdalena during his survey with already described species from other drainages instead of recognizing that he was dealing with a unique river system with, more likely than not, unique (almost relic) fish populations) left over from when the Amazon and Orinoco were conneted and drained north into the Caribbean.
-Shane

[König Löwe]

The Lasiancistrus looks very much like <A HREF="http://www.l-welse.com/forum/index.php? ... ">L-312</A>

[Shane]

It does look like the same fish, but why is L-312 listed as coming from the "Rio Magdalena, Peru"? Is there also a Magdalena Peru or is it likely that we are talking about the same fish and it is from the Rio Magdalena Colombia?
-Shane

[kgroenhoej]

According to http://www.transfish.de it's from Rio Magdalena Colombia

-Klaus

[coelacanth]

This means that the Magdalena's fauna has been seperated from the rest of South America's fish populations since the Andes rose.

Fossil evidence indicates that the Magdalena once had a far more diverse ichthyofauna more typical of the Amazonian/Orinoco drainages. Following isolation it is thought that the less stable conditions led to local extinctions of those species unable to adapt to the changes. Fossil Colossoma from the Magdalena area are impossible to distinguish from the extant species, fossil Phractocephalus have been recorded from areas well outside their current range, and also Arapaima.
There are other interesting questions about the fish from this area though, such as the origins of 'Geophagus' steindachneri.
Pete