On Saturday 11 May 2002, we headed out to do some collecting in the Rio Aragua and the upper Rio Tuy. This was my first chance to get back to the field since Expedicion Corroncho ended in late March. During my last trip to the Aragua I had found F. acus, however in my excitement over finding this fish, I did not snap any good habitat photos. I had also come across two other loricariids in the river, but I did not retain any specimens. Since that trip, I have become more fascinated with the genus Chaetostoma and I wanted to get specimens from the Aragua and upper Tuy to compare with specimens from the Orinoco drainage.
I was accompanied by Cindy and recent Venezuela arrival Mark, who is actually more into herps than fishes, but was none-the-less eager to go to the field with us. Despite the fact that the rainy season has started, we lucked out with a beautiful sunny day. I was also very surprised on arriving at the Rio Aragua that the water was low and crystal clear. Seining along the banks where there were overhanging bamboo branches and palm fronds once again turned up lots of Farlowella acus. Seining against the banks and around debris turned up two Rhamdia spp. (probably R. guairensis and R. quelen) and mataguaro (Crenicichla geayi) and in mid-stream we caught lots of Creagrutus tetras. As tropical streams go, this is a pretty sterile place and maybe the only body of water in Venezuela without guppies (OK, I guess I have become jaded when I call a creek with five catfish spp. "sterile.")
After some general sampling, we went right for the loricariids. We used a method that Jools, Don Kinyon, and I had perfected in the Rio Zuata where one person slightly lifts the stone an inch off the substrate while the other two gently bring the net under the stone. Once the net is in place, just lift the stone out of the water and the loricariids will drop off into the net below. Collecting in this manner is hard work, but very rewarding in terms of catching lots of fish. The same method is used with driftwood chunks to collect Panaque nigrolineatus, Hypostomus, L 94, Hypoptopoma, Panaque maccus and others in the Orinoco basin.
On my last trip, I called the loricariids I caught L122, boy was I not paying attention. As it turns out, there are actually two species of Chaetostoma in the Rio Aragua. C. pearsei is a smaller dark grey fish with scattered tiny white dots on the dorsal surface of the body. The caudal edge is trimmed with a thin white band that turns orange at the top and the bottom of the fin. The second fish, which I had earlier mistaken for L122, turned out to be Chaetostoma guairense. The colour pattern of this fish is almost exactly the same as L122's, but the fish is obviously a Chaetostoma. I kept several examples of each species to take home and compare with material from the Orinoco.
We left the Rio Aragua about 10:00 am and drove down the old highway towards El Concejo. Just after El Concejo, there is a bridge that spans the Rio Tuy and we stopped to take some samples. This should have been very close (if not the same spot) where Eigenmann collected specimens for his 1920 "The fishes of Lake Valencia, Caracas, and the Rio Tuy at El Concejo." The Tuy was not as calm as the Aragua and was actually quite sediment laden and moving along with a good current, that made collecting difficult. The water was also chilly and I estimated the temperature at close to 70F, which was about four degrees cooler than the Aragua. At this location, we managed to catch only guppies, Creagrutus and more Chaetostoma guairense. Wet and tired (but happy!), we decided to call it a day.
After returning home I was able to confirm the identifications of the two Chaetostoma species. I also compared the Chaetostoma sp. from the Rio Zuata (labelled in aqualog as L187) to the described and recorded spp. from Venezuela and this fish does not match any of the descriptions. The only other sp. with a long dorsal fin (I,9) is C. venezuelae which has only been recorded from eastern Venezuela. However, C. venezuelae has a slightly concave caudal fin edge (versus straight in the Rio Zuata species), no black spot at the anterior base of the dorsal fin, two cheek spines (versus 6-7 in the Rio Zuata species), and the adipose fin may be present or absent (versus always present in the Rio Zuata species).
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