Chaetostoma Stew

A spawning account of Chaetostoma cf. thomsoni
by Derek Heath

As the old saying goes, to make a rabbit stew you must first catch a rabbit. Likewise before you can spawn your Chaetostoma you must first get a pair of Chaetostoma. Obvious perhaps but sometimes the obvious is the hardest part.

I had wanted to try my hand at breeding Chaetostoma cf. thomsoni also known as bulldog or rubber-lipped plecos for quite some time. At first I was put off by comments I had heard to the effect that these fish could be very difficult to keep alive, let alone breed. After searching the Internet for information on this genus I decided there were three main requirements that may be essential to the successful maintenance of these fish. They appear to come from very fast flowing streams and rivers, often at a high altitude. Consequently it follows that they would probably prefer cooler temperatures and a vigorous current both of which would maintain high oxygen levels.

I set about arranging a tank 75x30x36cm (l.w.h) that I felt would give the best chance of success. Male Chaetostoma will “dig” their own spawning cave under rocks or wood, working away until they have produced a “cave” to their liking. They will not use ready-made caves or holes in wood, as many other Loricariidae will. To accommodate this requirement, small rocks of 6-7cm diameter were placed on the tank bottom and the gravel (3-6mm in size) was poured in to flow around and over these stones. Several pieces of slate were then nestled into the gravel until they were resting on top of the stones. This would prevent the slate from moving and potentially crushing the fish while they excavated their “caves”. At the back right corner of the tank I placed a small power filter (basically a powerhead connected to a sponge filter). In front of this filter and running along the side of the tank was a 15cm air bar. The flow of air caused the water surface at this point to raise 10 – 15mm above normal and this created a good circular current flowing up the right hand side of the tank along the surface and back along the bottom of the tank. Hopefully this would give the impression of a riverine environment. A piece of driftwood with some Java Fern was placed about half way down the tank. This served several potential purposes. Firstly many Loricariidae need cellulose in their diet. Secondly it created some eddies in the current which allowed food to drop to the bottom in concentrated feeding areas. Again many Loricariidae will only travel a short distance from their cave in the search for food and lastly the overhanging roots of the Java Fern provided additional areas for the fish to hide and feel secure. Although the tank did not have a heater, it was in my fishroom and was maintained at a temperature of 20-22^oC.

Fortunately some more Chaetostoma cf. thomsoni finally turned up for sale. These were juvenile fish, only 6-8cm in length. I chose 4 fish in all, two of them a little bigger than the other two. This was the only indicator I had to go on at the time, which may have distinguished males from females. Luckily this turned out to be correct and I ended up with 2 pairs. I finally had my pair of Chaetostoma. It was time to make “Chaetostoma Stew”

The fish were placed in the tank and allowed to grow and become sexually mature. Initially they were fed a range of foods such as flake, frozen bloodworms, daphnia and green vegetables such as zucchini, cucumber and silverbeet. I was never sure if they were eating anything and eventually they were fed solely on flake food.

In the wild many catfish spawn in the rainy season. During the previous “dry” season they experienced rivers and streams with the low levels (perhaps no more than a collection of puddles) and slow currents. The temperature of the water increased, as the levels dropped, and food becomes scarce. But once the floods arrive, this all changes almost overnight. The rivers again become a torrent, increasing in level until they break their banks and flood onto fertile lands providing increased food and spawning sites. The temperature of the water also drops with the large influx of water from rain or melting snow in the mountains.

Prior to their first spawning, these conditions were duplicated in the aquarium. I would like to say that this was done on purpose but the truth is it was all an accident. During most of last Summer I became disillusioned with fishkeeping and consequently my fish did not get all the care and attention that they deserved. The Chaetostoma were lucky they were fed let alone if they had a water change. On top of the reduced feeding and water changes, unnoticed, the filter had stopped working as well. Even the flow of air to the airbar had reduced due to a perforation in the diaphragm of the air pump. So for a couple of months these fish were fed much less than normal, their water quality declined, the flow of water was reduced and the temperature increased a few degrees from the summer heat. Due to the lack of filtration a small but noticeable amount of mulm was starting to collect on the bottom.

Once I noticed how bad things had become I set about correcting them. Firstly the airpump was fixed and the filter was replaced with an air driven box filter filled with filter wool. Secondly 25% cold water changes were done each day for 5 days, this effectively replaced about two-thirds of the water and finally they started getting fed everyday. About a week later, immediately after a 10% water change, I discovered three fry in the tank. When I first observed the fry (with partially absorbed yolk sacs) they were clinging to the roof of the spawning site, the rest had obviously already left the “nest”. It was 7-8 days later before I started to consistently see fry "grazing" on the glass, rocks and gravel. I assume they take this time to use up their yolk sac. They are very shy and if they spot movement they move at a speed that makes it appear as if they have simply disappeared. If not out feeding they stay under cover.

Unfortunately I did not record the water parameters either at the time of the corrective action nor at the time these fry were first noted. Presently the conditions are 4dGH, pH 6.8. Temp. 20OC.

Since noticing those first fry the Chaetostoma have continued to spawn every 3-4 weeks. Presently the male is guarding his forth batch of eggs. 2-3 days prior to spawning the female can be seen near or even in the spawning cave. At all other times the male vigorously defends this area from all comers, including the female. Spawning itself appears to take place during the night and the eggs are placed on the roof of the cave in a small clump about 3 layers thick. They are about 4mm in diameter and of a creamy yellow colour. The females work is done at this point and the male takes the sole role of guardian. He is very diligent at this. I have never seen him leave the cave, even for food during this period. However he will continue to protect the cave entrance should any other fish get to close. At all other times the male stays in an inverted position with his ventral fins completely covering the eggs, these he uses to gently fan the eggs. At 20 ^oC the eggs take about 10 days to hatch. On hatching the fry instantly leave the cave. This differs from what Rob Torrens says in his article on spawning Chaetostoma cf. thomsoni (planetcatfish.com) “The fry, right after hatching, consisted of a yolk sac with a tail and eye development occurred over the next two days.” This apparent discrepancy is probably due to the difficulty I have in viewing the eggs/fry in the cave. Looking through a small opening while the male still occupies the cave makes it difficult to determine much else other than the fact that eggs are present. Under these conditions newly hatched fry with a large yolk sac may appear to look like eggs. Alternatively this male may not be a good parent and once hatching occurs immediately pushes the fry from the cave. I have had a male Bristlenose (Ancistrus lineolatus) which did the same. The fry take finely ground flake food immediately but they may be getting some of their nutrition from the mulm in the tank. I have seen no signs of predation from the parents, which is just as well as I find it almost impossible to catch the little suckers without destroying the entire setup.

Just prior to spotting the first three fry, a storm front moved through the area after a long settled period of fine weather causing a drop in barometric pressure. However there is some doubt in my mind if any of the above caused the spawning. If my recollection of the timing of events is correct, then those initial three fry had to come from eggs laid 12-13 days earlier. At this stage the tank was still in its original neglected state. So exactly what the initial trigger which caused the fish to spawn was, remains uncertain.

To summarise, some of the ingredients for making “Cheatostoma stew” are, a fertile pair, appropriate spawning sites, cooler temperatures, good aeration and current, putting the fish through a dry – rainy season cycle and possibly a drop in barometric pressure. The ingredients should be added in the correct order and allowed to “simmer” until it reaches the “boil”. Simmering time will vary depending on personal experience.