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Tilapia ruweti by Paul Loiselle |
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The availability of a selection of Lake Bermin’s endemic Tilapia species to aquarists on both sides of the Atlantic has put to rest—hopefully for good—the conventional perception of tilapias as drably colored cichlids whose large adult size recommends them to the table rather than to the aquarium. The Bermin tilapias are vividly colored and few species grow much more than 6 inches (15 cm) SL (Dickinson, 2007). Indeed, one species, Tilapia snyderae, is small enough to qualify as a dwarf cichlid (Loiselle, 2008). However, T. snyderae is neither the only dwarf Tilapia species nor the first to make its debut as an aquarium fish. That distinction goes to the subject of this article, Tilapia ruweti. | |
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A combination of elaborately-patterned and very well-developed vertical fins and unequally-bicuspid jaw teeth led this species to be originally described as Pelmatochromis ruweti by Max Poll and Dirk Thys van den Audenaerde in 1965. The holotype was collected from Lake Lufira, an artificial impoundment located in the Democratic Republic of the Congo’s Shaba—then known as Katanga—Province. Contrary to the usual fate of such specimens, this fish was brought back alive to the Aquarium of the University of Liège in Belgium. This doubtless accounts for the extraordinarily detailed half-tone illustration of the holotype in the species’ description as well as the unusually complete description of its life colors. Additional type material came from several localities in the Angolan portion of the Congo River drainage. In a subsequent revision of the genus Pelmatochromis as broadly understood, Thys (1968a) noted that this species actually had far more in common with Tilapia sparrmanii A. Smith 1840, type species of its genus, than to any nominal Pelmatochromis species and changed its generic placement. Tilapia ruweti is now firmly ensconced within the subgenus Tilapia, along with T. sparrmanii and two other southern African species, Tilapia guinasana Trewavas 1936 and Tilapia baloni Trewavas and Stewart 1975. This species made its aquaristic debut very shortly after its scientific description. I first heard about the newly available “Microtilapia” in 1967 from Kappy Sprenger, an enthusiastic cichlid hobbyist with whom I corresponded while serving as a Peace Corps volunteer in Togo. On the basis of a sketch that Kappy sent me, I was able to identify the “Microtilapia” as T. ruweti. This species was one of the first cichlids I kept and bred when I returned to the United States from Africa in 1971. At that time, I assumed that as was the case with so many other cichlids native to the Congo, we owed the availability of this delightful species to the efforts of the late Pierre Brichard, who pioneered the export of ornamental fishes from central Africa. However, when I asked Pierre about this the first time he spoke to an A.C.A. convention, he informed me that this was not the case. While he had gone to Shaba in an attempt to find T. ruweti, his efforts were unsuccessful. The aquarium strain of this species clearly originated elsewhere in Africa. | |
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Subsequent surveys of the ichthyofauna of southern Africa have revealed that T. ruweti is by no means endemic to the Congo River basin. It transpires that this species enjoys a much wider distribution, occurring in the headwaters of the Zambezi River in Zambia and Zimbabwe and as its South African vernacular name Okavango Tilapia clearly implies, in Botswana’s Okavango River as well (Skelton, 1993). As ornamental fishes were being sporadically exported from South Africa in the 1960s and early 1970s, it seems reasonable to suggest that the founders of the original aquarium strain of T. ruweti were collected from either the Zambezi or the Okavango basin. That the coloration of the original aquarium strain differs in a number of details from that of the topotypical population but corresponds quite well to that of the Okavango-Zambezi fish illustrated by Skelton lends further support to this hypothesis. Males of this species can reach 3 inches (c. 7.5 cm) SL in nature, while maximum size for females is usually an inch less. Given the small size and attractive coloration of T. ruweti, its solid establishment among the ranks of aquarium fish would seem to have been assured. The actual fate of the initial captive population was actually quite different. While this hardy and easily bred species was initially received with enthusiasm by cichlid hobbyists, within a relatively short time its popularity was eclipsed by the seemingly endless stream of spectacularly colored cichlids being exported from Lake Malawi. As its popularity waned, so did any interest in breeding it. A species that has made it into commercial production is to a certain extent buffered from abrupt swings in popularity. However, fish farmers in Florida were precluded from working with T. ruweti by a state prohibition against the commercial production of Tilapia, while this species seems never to have sparked the interest of breeders in the Far East. As nothing comparable to the American Cichlid Association’s C.A.R.E.S. program existed at the time, T. ruweti slipped quietly into aquaristic oblivion. By the time this species was profiled in the A.C.A.’s Cichlid Index (Loiselle, 1979), it had disappeared from the tanks of aquarists on both sides of the Atlantic. | |
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Given both the degree of insecurity arising out of the turbulent political history of the Democratic Republic of the Congo from 1980 to the present day and the fact that the export of ornamental fish from South Africa had ceased well before the disappearance of T. ruweti from the aquarium scene, it seemed most unlikely that cichlid enthusiasts would ever again have a chance to work with this species. I was thus very pleasantly surprised when in 2011, I learned from my Austrian colleague Anton Lamboj that T. ruweti from the type locality in Shaba Province had been imported into Europe and successfully bred. I was even more pleased at his generous offer to send me some of these F1 fry, which I eagerly accepted.
Tilapia species have a reputation as “industrial strength” cichlids able to prosper over a wide range of water conditions. Tilapia ruweti is no exception to this rule. I have maintained and successfully bred this species in both soft (3° to 7° DH general and carbonate hardness) and moderately hard (14° to 20° DH general and carbonate hardness) water. Like many other fishes native to marginal habitats in a part of the world with pronounced rainy and dry seasons it experiences a rather wide range of pH over the course of a year’s time. This probably explains why T. ruweti is also tolerant of a rather broad range of pH values in captivity. I have had pairs spawn successfully at pH values between 5.5 and 7.8. This species is considerably less tolerant of elevated nitrate levels. High concentrations of nitrogen cycle byproducts both depress reproductive activity and leave T. ruweti susceptible to systemic bacterial infections. Given this species’ robust appetite, efficient biological filtration combined with a program of regular and frequent partial water changes is essential to its successful maintenance. | |
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Although a water temperature between 70 °F – 80 °F (21 °C – 26.7 °C) is recommended for day-to-day maintenance, with an increase to 82 °F – 85 °F (27.8 °C – 29.4 °C) for breeding, this species is capable of surviving much cooler conditions. After “Hurricane Sandy”, I was without electricity for eleven days. Water temperature in my aquariums dropped into the low 50 °F (10 °C) range two days after the storm and remained there until power was restored. I lost all of my West African cichlids within a few days of the power outage, but my group of topotypical T. ruweti not only survived what I have come to think of as the “Big Chill”, but spawned three days after the restoration of power and a return to a more “tropical” water temperature in their aquarium! In nature, T. ruweti feeds upon aquatic invertebrates and organic detritus, including some plant matter. While it displays a marked preference for live or frozen food in captivity, this species will also enthusiastically devour any of usual prepared foods. I feed my fish frozen Mysis and Spirulina-based flakes on alternate days, with frozen bloodworms or glassworms as an occasional treat. Readers who like cichlids that respond positively to them will love this species. Like most tilapias, T. ruweti makes the connection between the appearance of its keeper and that of food almost instantaneously. My fish practically climb out of their tank when they see me approach. This poses a considerable challenge to photographing them, as this “begging” behavior will persist for up to half an hour even in the absence of any positive reinforcement. Hope clearly springs eternal in the tilapiine breast! This species will also “graze” on the biocover that develops on submerged wood and seems to do better when afforded the opportunity to do so. | |
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As it does not share the aggressively herbivorous tendencies of many other Tilapia species, T. ruweti can be kept safely in a planted aquarium. The only risk to the aquascaping is likely to come when the fish breed. While not compulsive diggers, pairs of this species do engage in a certain amount of substratum-shifting in conjunction with spawning. Rooted plants in close proximity to the spawning site are thus at risk of being dislodged. One can minimizing the likelihood of such an eventuality by growing strongly rooted plants like Anubias in pots rather than planting them directly in the tank’s substratum. Sexually quiescent T. ruweti are moderately social cichlids. It is possible to keep a group of six to eight individuals in a 29 gallon (120 liter) aquarium until the onset of reproductive activity. At this point, the first pair to spawn will proceed to make life progressively more unpleasant for their conspecific tankmates, who should be moved elsewhere. When not reproductively active, this species will share quarters amicably with other cichlids of comparable size and temperament. Pelvicachromis and Anomalochromis species are appropriate tankmates, as are such robust Apistogramma species as A. steindachneri. As it occurs syntopically with an interesting assortment of haplochromine cichlids, it is not surprising that T. ruweti can also hold its own when housed together with riverine Astatotilapia species. | |
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The behavior of this species towards non-cichlid tankmates is exemplary. I have housed T. ruweti with smaller tetras, danios, rasboras, and barbs without encountering any problems. Poeciliids will also share quarters successfully with this species, whose indifference extends even to their newly-dropped fry. As this tolerance diminishes markedly once a pair has free-swimming fry, prudence would suggest removing non-cichlid tankmates as soon as eggs are noticed unless the tank is large enough to allow them to keep well clear of a pair’s territory. I have never kept T. ruweti together with Corydoras species, but given the strong negative response that catfish elicit from substratum-spawning cichlids, I suspect that parental T. ruweti would make life thoroughly miserable for any representatives of the family Callichthyidae. Possibly because they never displayed any interest in either cichlid eggs or fry, Ancistrus and Panaquolus species housed with breeding pairs of T. ruweti were ignored. Tilapia ruweti is a biparentally custodial substratum-spawning cichlid. Courtship behavior is rather simple and can be initiated by either sex. It consists of reciprocal lateral displays and ritualized digging by both partners. That said, I have observed noteworthy differences with regard to a number of features between the reproductive behavior of the original aquarium strain of this species and the present topotypical population. The first has to do with the choice of spawning site. Pairs of the original strain either cleaned a small rock or else dug down to their tank’s bottom and spawned thereupon. I have observed eleven spawnings by three pairs of topotypical T. ruweti. In every instance, the eggs were placed upon a vertical surface, either the tank wall or a piece of driftwood. Of the many other Tilapia species I have bred, only T. guinasana has consistently displayed such a propensity for spawning on a vertical surface (Loiselle, 2001). | |
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Pairs of both populations produced rather loosely structured plaques of ovoid, olive-green eggs. The eggs measure 1.2 mm (c. 0.05 in) along their major axis. Spawns can number up to 300 eggs. Such clutches are decidedly on the small side by Tilapia standards, but still represent a respectable reproductive effort by a species whose females rarely exceed 2 inches (c. 5.0 cm) SL. The eggs hatch in 72 hours at 80 °F (25 °C) and the fry are free-swimming three days later. As is the norm for the genus, hygienic behavior towards and close-in defense of the developing eggs and yolk-sac fry are primarily the female’s responsibility, while the male concerns himself with keeping intruders from crossing the boundaries of the pairs territory. That said, the males of my pairs were not averse to relieving their consorts long enough to allow them to snatch a few mouthfuls of food. The second notable difference between the two strains has to do with how pairs manage their newly hatched fry. Pairs of the original aquarium strain would usually move yolk-sac fry to previously dug pits adjacent to the spawning site. However, on several occasions, the female of pairs housed in tanks with a heavy cover of floating fern (Ceratopteris sp.) hung the newly hatched fry from the roots of these plants, in a manner reminiscent of the Central American Herotilapia multispinosa and the various South American Mesonauta species. Although I cultivate Ceratopteris in all my tanks, I have yet to observe this behavior in my pairs of topotypical T. ruweti. As the one feature these otherwise very dissimilar cichlids have in common is a tendency to breed in habitats with extremely soft bottoms and relatively low dissolved oxygen levels, I have interpreted fry-hanging behavior by the original aquarium strain of T. ruweti as an adaptive response to frequently encountered low dissolved oxygen levels in the wild that carried over under aquarium conditions. I have not to date had the courage to pull the plug on the outside power filter that serves the tank housing a breeding pair of my present population to determine if this will trigger comparable fry-hanging behavior! | |
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Both parents are actively involved in the defense of the mobile fry. For the first few days, the parents can usually manage to keep their fry concentrated within a restricted area and have no difficulty in protecting them from potential predators. However, as the young fish grow a bit older, they tend to disperse more widely. It is at this point that significant fry mortality occurs when the fish spawn in a community setting, as the adults are incapable of protecting such straying offspring. An interesting twist on the usual pattern of custodial care demonstrated only by a single pair of the original aquarium strain. On several occasions, the male of the pair responded to disturbance by taking the free-swimming fry into his mouth and holding them until the perceived threat had passed. Such behavior is the norm for most larvophile and even some ovophile mouthbrooding cichlids—the various Benitochromis and Chromidotilapia species come to mind in an African context. However, I am unfamiliar with any observations of such behavior from other Tilapia species , although there is circumstantial evidence suggesting it may be practiced by Tilapia discolor, a species endemic to Ghana’s Lake Bosumptwi (Thys, 1970). In any event, Parental care under aquarium conditions rarely lasts longer than three weeks. At this point, the female is capable of spawning again. Parental care drops off dramatically as the pair begins to prepare to spawn again. The older fry are no longer tolerated within the pair’s territory and will be killed and eaten if they cannot move beyond its boundaries. This situation arises because the food intake of parental fish is essentially unchanged in a captive setting. In nature, parental cichlids cannot simultaneously forage and effectively protect their fry. They typically subsist on fat stores until their fry attain independence. This strategy effectively precludes prompt re-spawning, as the female lacks the ability to mature another clutch of eggs. Aquarists who desire to prolong the period of active brood care can inhibit prompt re-spawning by both reducing the food intake of the parental fish and lowering the temperature in the breeding tank. | |
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A third significant difference between these two populations of T. ruweti relates to the size of the free-swimming fry. Newly mobile fry of the original aquarium strain were large enough to take Artemia nauplii as their initial meal. Those of the present strain are not, as I discovered the hard way. These need to be fed microworms for several days before they are capable of managing newly-hatched brine shrimp. After a few days on Artemia nauplii, it is feasible to add a prepared fry diet such as Hikari’s First Bites© and frozen Cyclops to their menu. As the fry are as voracious as their parents, frequent partial water changes are essential to successful rearing. If due attention is given to this aspect of their maintenance, rearing poses few problems. Despite their healthy appetites, T. ruweti fry are initially rather slow growers. It takes about a month before they are large enough to show a distinct Tilapia spot in their soft dorsal fins. Once this point is reached, growth accelerates considerably. Under optimum conditions, the fish attain sexual maturity fourteen to sixteen weeks post-hatching, at 1.25 inch (c. 3.0 cm) SL for males and just under 1 inch (c. 2.0 cm) SL for females. In my experience, cichlids characterized by extreme reproductive precocity are not particularly long-lived. Such species are typically found in habitats that are either ephemeral or markedly unpredictable. Frequently they are both. Under such circumstances, the sooner an individual breeds, the more likely its genes will be represented in the next generation. As available data (Skelton, 1993) suggest that T. ruweti is characteristically found in just such habitats, it should thus come as no surprise that natural selection has favored reproductive precocity over longevity in this species. This species’ susceptibility to systemic bacterial infections increases quite markedly by the end of their second year, as does its reproductive output. This, I suspect, is one of the factors that contributed to the disappearance of the original aquarium strain of this species. Hobbyists that held off rearing the progeny of early spawns believing that they had plenty of time to rear the next generation of breeders discovered too late that such an assumption was erroneous. The take-home message is simple: Don’t defer rearing the next generation of this species! | |
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The conservation status of T. ruweti, unlike that of far too many cichlid species, poses little cause for concern. This species enjoys an extensive range which includes extensive regions where human activity has had—and in the foreseeable future is unlikely to have—minimal impact. However, this state of affairs does not automatically assure its future as an aquarium fish. Indifference led to the disappearance of T. ruweti from the hobby once before. Thanks to a fortunate combination of circumstances, cichlid enthusiasts once again have the opportunity to enjoy this delightful little fish. Given the vagaries of African politics, it would be extremely unwise to count on a third chance at establishing a managed population of this species if history is allowed to repeat itself. The American Cichlid Association’s C.A.R.E.S. Program was established both to assure the survival under management of cichlids whose survival in nature is either presently at risk or apt to become threatened as well as to perpetuate aquarium populations of species which while secure in nature, would, if lost to the hobby, be for any number of reasons, extremely difficult to re-import. As T. ruweti clearly falls into the second category, I have strongly recommended that it be added to the roster of C.A.R.E.S. species. Given the small adult size and attractive coloration of this species, it clearly has considerable commercial potential. If the regulatory climate still precludes the large-scale production of T. ruweti in Florida, hopefully enterprising fish farmers in the Far East adopt this species as enthusiastically as they have Anomalochromis thomasi. | |
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Dickinson, C. L. 2007. The endemic Tilapia of Lake Bermin. Cichlid News 16(1): 22–27. Loiselle, P. V. 1979. Tilapia ruweti (Poll and Thys 1965). American Cichlid Association Cichlid Index 4(8): 1–2. Loiselle, P. V. 2001. Aquarium husbandry of the Harlequin Kurper, Tilapia guinasana Trewavas 1936. Cichlid News 10(1): 6–14. Loiselle, P. V. 2008. The aquarium husbandry of Tilapia snyderae, a dwarf cichlid from Lake Bermin, Cameroon. Cichlid News 17(2): 16–22. Poll, M. & D. F. E. Thys van den Audenaerde. 1965. Deux cichlidae nouveaux du Sud du Bassin du Congo. Rev. Zool. Bot. afr. 72(3-4): 322–333. Skelton, P. 1993. A Complete Guide to the Freshwater Fishes of Southern Africa.Southern Book Publishers, Grahamstown, pp. 1–388. Thys van den Audenaerde, D. F. E. 1968a. A preliminary contribution to a systematic revision of the genus Pelmatochromis Hubrecht sensu lato. Rev. Zool. Bot. afr. 76(3-4): 351–391. Thys van den Audenaerde, D. F. E. 1968b. An annotated bibliography of Tilapia (Pisces, Cichlidae). Mus. Roy. Afr. Centr. Doc. Zool. (14): 1–406. Thys van den Audenaerde, D. F. E. 1971. The paternal mouthbrooding habit of Tilapia (Coptodon) discolor and its special significance. Rev. Zool. Bot. afr. 82(3-4): 285–300. |
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