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by Ted Judy |
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I traveled to Gabon in February, 2011, for a whirlwind tour of the northern region of the country collecting fish and having the experience of a lifetime. The trip took us from Libreville in the west to the city of Makoukou in the far east, through regions of densely forested highlands and river bottoms. We collected in many locations and found a huge diversity of species of interest to aquarists. The target species included any of the Parananochromis that are found in Gabon. We found several, and I was fortunate to make it home with two of them: P. brevirostris and P. gabonicus.
A big challenge to obtaining rare fish is researching their care and husbandry needs. There is not a lot available, and what information can be found is mostly a reiteration of another person’s report. The reality is that very little is known about Parananochromis in general, and probably less about how to successfully keep and breed them in captivity. |
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I have some experience with representatives of the genus through keeping P. longirostris and P. caudifasciatus (both imported from Cameroon). I had no success breeding the larger P. longirostris, but the smaller P. caudifasciatus was very willing to reproduce. Unfortunately, the sex ratio of the fry was heavily out of proportion and after a couple of generations the line was lost. That situation is commonly reported for the species, and the few spawning reports I was able to locate for P. brevirostris described the same problem. I was not able to find a specific spawning report for P. gabonicus, other than ‘reproduces like others of its genus’. The few people I talked to who had and bred any of the Parananochromis species reported that poor sex ratios were a common problem.
Sex determination in fish is not the simple matter of chance inheritance of a specific sex chromosome as it is in mammals. That type of inheritance, though the norm for us, is actually the exception in the animal kingdom. Many fish have their gender influenced by the chemical and temperature environment in which the eggs are incubated. Some of the best-known examples of this are the cichlids of the genus Pelvicachromis, which are not too distantly related to Parananochromis. The question is… what is the deciding factor? Temperature? pH? General hardness? Nobody knows for sure, and it is possible that any or all of these factors can play a role. |
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My challenge was to try to breed the fish in an environment conducive to getting a good sex ratio in the offspring. Considering that there is not a lot of pertinent information available from research, and the few accounts I did find resulted in skewed sex ratios, the best plan was to toss out any preconceived notions and start with what I know from observations in the wild.
The P. gabonicus were collected west of the city of Mitzic on the road to the town of Sam (near the border of Gabon and Equatorial Guinea), in a small stream under a dense canopy of a huge species of bamboo. The surrounding countryside was mostly cleared for agriculture, broken by strips of low-lying land with a stream and the bamboo habitat. The stream banks were shallow, and the flood plain wide with residual pools of water adjacent to the main channel (no fish were found in the pools). The soil of the flood plain was humus-rich, and the sediment in the stream was similar: a lot of plant detritus over a sandy bottom, with very tannin-stained ‘black’ water. The water parameters at this location on the day we were there would qualify as very soft and acidic. The pH was 4.0, conductivity 12 µS, GH 0 and KH 1. The temperature was a cool 74°F (23°C), as compared to stifling heat and humidity of the air around us. We did not measure available oxygen, but water flow through the stream and a shallow depth suggest that the water was well oxygenated. We were collecting in Gabon’s rainy season, but on this day the water was clear enough to see the bottom, at least to the depth permitted by the dense staining by tannin. |
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The biodiversity in the stream was high, attesting to the fertility of the rainforest habitat of the area. We collected several species of tetras, barbs, killifish, mormyrids, catfish, shrimp, and the one species of cichlid, P. gabonicus. Adult cichlids in breeding color were found, as well as many juvenile fish and fry. The young fish were found throughout the stream, but mostly congregated in shallow, low flow areas with deep accumulations of leaf litter. The adults were found in deeper pools, but also associated with leaf litter. Once nets had disturbed the habitat, the best way to find more cichlids was to scoop up masses of the leaves and pick through them. It appears that the fish responded to danger by diving into the detritus.
The P. brevirostris were collected in a very different habitat. The location is a stream called the Menguegne west of the town of Ndjole along the road to Bifoun. The Menguegne is a northern tributary of the Ogooue River, the large waterway that bisects Gabon into north and south. The stream is large with deep banks, suggesting that during strong rain events the runoff through the channel becomes powerful. The banks were forested with a mix of deciduous trees and bamboo. The soil was sandier than at the location where we found the P. gabonicus, but the thick leaf litter and associated humus was still present. There had been some rain the day before our visit to the location, and the water was carrying some sediment that reduced visibility in the deeper pools. The channel is broken by alternating shallow riffles and deep pools, some of which are close to a meter (3.3 ft) in depth or more. There many logs and branches in the stream, creating an array of structure for fish. Leaves accumulate in areas where the current slows down, and some of these patches spread across the center of the stream for several meters (several yards). Those leaf beds would prove to be significant. The pH of the Menguegne measured 6.5, significantly higher than the location previously described. The conductivity was 35 µS, GH 0 and KH 0. The temperature was a relatively warm 79°F (26°C). |
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The diversity of fish species in the Menguegne is also high, and includes several species of fish similar to the location on the road between Mitzic/Sam, with the notable additions of the freshwater pipefish Enneacampus ansorgei and three species of cichlids: Chromidotilapia regani, C. kingsleyae, and P. brevirostris. The presence of multiple species of cichlids can be attributed to the diversity of habitats in the stream. The larger Chromidotilapia species were netted close to and among the logs and branches, while the smaller P. brevirostris were closely associated with the piles of leaf litter. So much so that we were able to capture P. brevirostris in large numbers and of all ages by using a seine to dredge up the large accumulations of leaves in the slow, open areas of the stream.
Once the fish were home and acclimated, the task was to decide how to set them up to spawn. I had plenty of time to work this out, because most of the fish I made it home with were juveniles that would not be ready to breed for a few months… or so I thought. Tragically, P. brevirostris can be a nasty little beast, and within two days of being home I was left with a single male. Territorial males will not tolerate the presence of another male in a small space. My mistake for trying to form a pair in the same way I use for other west African cichlids, by putting three of each sex together and letting them work out who will mate who. The result with P. brevirostris is… the survivor. |
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I chose to house the cichlids as single pairs in 20-gallon (76 L) aquarium because of the high level of aggression towards extra fish in the tank. I had three pairs of P. gabonicus, one pair of P. brevirostris and three adult female P. brevirostris, each in a tank of her own. My plan (which worked) was to rotate the male P. brevirostris between ripe females, leaving females with fry alone to raise their broods. I have observed several spawns of each species, and rarely see the males provide much in the way of brood care. Keeping the male in with the female and her fry usually resulted in the male being driven from the vicinity of the brood. That pattern changed, as I will describe, when I moved the breeders to large aquariums. Matching the natural water conditions is a good starting point when trying to breed a rare species, and since I had first-hand knowledge of where the fish were collected I pretty much tossed out anything I had read. Water parameters listed in a book or article are usually a snapshot in time and place, just as the readings we took in Africa are, so a statement of the pH, temperature, and hardness does not paint the entire picture. Use them as guidelines, and be prepared to deviate from them if the fish do not breed. I started all the cichlids in reverse osmosis water reconstituted to a KH 1 by the addition of a very little amount of carbonate buffer. Then I used a commercial pH reducer to drop the pH in the P. brevirostris aquariums to 6.0 and in the P. gabonicus aquariums to 5.0. Adding the chemical increased the conductivity of the solution to over the low levels in the wild, but there is no calcium or magnesium ions in the pH reducer (the bulk of which is sodium chloride), so the general hardness (GH) did not increase. In my experience, conductivity is not as crucial as GH, KH, and pH can be (and they are frequently not crucial at all). |
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Each aquarium was furnished with a pile of bogwood, a few spawning caves with small openings, clean sand as a substrate and some free-floating Anubias plants. The light was subdued and on a 10 hour light and 14 hour dark schedule. The fish were fed a variety of foods as befit their omnivorous diet, with regular feeding of live daphnia, black worms, and Artemia nauplii to condition the females for spawning. The females were displaying pinkish abdomens within a couple weeks, and the first signs of spawning came shortly after. The P. gabonicus were quickest out of the gate, and I am sure that two of the females laid eggs that did not hatch. The fish never appeared to be truly comfortable with the spawning sites. Thinking back to observations made in the streams, I started to consider the role of microhabitat. The high stakes game of reproduce or die suggests that fish (or any other living thing, except possibly us) do not choose things without a reason. The place in which a fish chooses to lay its eggs is purposeful. Though I do not have a concrete observation to prove it, I suspect that the natural spawning sites for these two Parananochromis species is deep under the piles of leaf litter in the streams they come from. If my hunch is correct, then the site where the fish lay the eggs is probably surrounded by plant detritus, and would probably have a pH much lower than the flowing water in the stream above. I tested the hypothesis by reducing the number of caves in each tank to two. One cave was left alone, but the other was stuffed with long-fiber sphagnum moss. Both caves were located next to each other in the back of the aquariums, behind the bog wood, but positioned so I could see their entrances. Within a day the only caves that the females gave any attention to were those with moss. Within a week there were spawns with two of the P. gabonicus pairs, and with the P. brevirostris pair, which had not shown much interest before. Fry rearing for both species proceeded in the standard chromidotilapine fashion, with the exceptions that the male was only loosely associated with the task, and that the female P. gabonicus would bring all the fry into her mouth and retreat to the cave when she perceived a threat. She would keep the fry in her mouth, even venturing out to confront the male, for several minutes before releasing the fry. Considering that there are other genera in the chromidotilapines that display some level of mouthbrooding (most notably Chromidotilapia and Benitochromis species), the mouthbrooding behavior of the females does not surprise me. The female P. brevirostris, however, did not mouthbrood (at least not while I was looking). |
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Now that the fish had produced fry I started to think about sex ratio. As the fry grew I spent a lot of time trying to find a characteristic that appears early in development to tell them apart. I was not able to do so until the fry were six months old, and when the changes occurred they literally happened over night. One day the grow out tank was full of fish of indiscriminate sex all living peacefully together, and the next a few males and females had decided to pair off and all bets were off. Luckily, the behavior of ‘destroy all others’ seemed tempered by cushy tank-rearing and the added space of being in a 75-gallon (284 L) aquarium to grow. As both species matured the sex ratios appear to be in the 60% female to 40% male range, which is not unreasonable. When I had bred P. caudifasciatus, I managed to get a total of two males in several hundred offspring. What did I do differently to get good sex ratios in both species? I have not made a scientific study of it, but I suspect that the secret is in two factors: the very low pH in the microhabitat inside the spawning cave and cool temperatures. The temperatures of the water in Gabon were considerably cooler than I had ever kept west African cichlids in before, and the first thing I did after getting the fish into tanks was to unplug the heaters. I also put all the breeding pairs in aquariums on the bottoms of my racks. There the temperature stays between 70–74°F (21-23°C) year round. I measured the pH in the caves with moss (using a meter with a narrow electrode housing that fit through the opening) at 4.5. That was half a point lower than the water in the P. gabonicus tanks, and 1.5 points lower than the water in the P. brevirostris tanks. I have since moved my adults into larger aquariums in groups mixed in with some of their juvenile offspring. Each group consists of at least two males and four or five females, plus up to a dozen juveniles from 0.5–1 inch (1.3–2.5 cm) in length. The tanks are heavily decorated with wood and moss-filled caves, and I have been keeping a layer of boiled oak leaves over the substrate to a depth of about three inches (7.6 cm). The fish have not been killing each other in this set up, and they are continuing to spawn. The water parameters are the same, so I do not expect to have any less success with maintaining good sex ratios. Parananochromis is a rare genus in our hobby, and when we manage to get them it is in our best interests to try to keep them around. Barring any unforeseen problems, I hope that the colonies I possess will be here for a long time. |
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