(This article was originally published in Freshwater and Marine Aquarium Magazine, Dec 1981; pp. 30-34, 76-79. It is here reproduced with the permission of author Dr. Paul V. Loiselle).
"Before you can make rabbit stew, You must first catch the rabbit" - - German Proverb.
Not long ago, I was involved in a friendly debate with a killiphile friend over which family, the Cichlidae or the Cyprinodontidae, comprised the most easily bred aquarium fishes. My friend stoutly defended the merits of non-annual killies, pointing out that one could find attractive species suited to virtually any water conditions which, when well fed, would spawn continuously despite any efforts their keeper might make to prevent them, Killifish fry, he further noted, are fully mobile at hatching and are very easily reared, for in most instances they are large enough to take Artemia nauplii as their first food. In many species, he concluded, adults will ignore their offspring if well fed, thus allowing the novice breeder to obtain fry in a permanent set up by simply introducing newly hatched brine shrimp on a regular basis from the tenth day of the adults' residence onward.
Not totally ignorant of the realities of killifish culture myself, I marshalled what seemed an irresistible rebuttal. While conceding the accuracy of his statements, I pointed out that to obtain killifish fry in substantial numbers, rather more labor was required than that entailed in keeping a group of breeding adults too stuffed to indulge in retroactive birth control. The eggs have to be removed from the breeding tank and hatched under controlled conditions. I paraded before him a vision of egg-laden spawning mops, whose contents must be carefully removed to hatching dishes containing water of the same chemical makeup treated to inhibit bacterial growth. I reminded him of the need to carefully monitor their contents over a lengthy incubation period and to remove unviable eggs before they infected their fertile counterparts. I conjured up visions of belly-sliders galore should conditions in the hatching container prove less than ideal.
To this onerous picture I contrasted the spectacle of piscine parenthood in its most elaborate form, exemplified by the biparental substratum-spawning cichlids. Here I argued, was the ideal fish for the laid-back aquarist. Just add food to the tank - the parents take care of everything else! I was not long destined to enjoy the illusion of victory, however. His eyes sparkling with the satisfaction of a warrior whose foe has opened himself to a mortal blow, my opponent delivered the coup de grace in this duel of words: "I don't deny for a moment what you say about cichlid family life is true - but before you can have a family, you have to have a pair!
Given that the question I am most frequently asked when I speak to aquarium societies deals, in one form or another, with precisely that issue, I was forced to admit that I had been hoisted with my own petard. In contrast to the case with most other egglaying aquarium fish, where the central challenge in their controlled breeding concerns the postspawning management of the eggs and fry, the chief problem facing the cichlid breeder is that of getting his fish to spawn in the first place. The experienced cichlid fancier tends to discount this aspect of the process because over the years he has learned the art of cichlid matchmaking on a trial and error basis. He can thus pretty well call the shots when working with an unfamiliar species as long as he knows its reproductive modality. To the neophyte, whose ignorance has usually been well buttressed with misinformation, it may rather seem as if the fish are calling the shots instead! Hopefully, this article will make successful matchmaking easier for the novice breeder while offering the experienced cichlid hand a better understanding of how and why his emperically derived approaches work.
To put the problem in perspective, let us look at how biparental substratum-spawning cichlids manage the business of pair formation in nature. We will, for the present, defer consideration of polygynous species, regardless of their reproductive modality. The aquarium literature (Innes, 1938; Sterba, 1966) describes the period leading up to spawning in such cichlids as an interval of intense interaction between the prospective partners characterized by a tremendous amount of reciprocal aggression that is ideally but not always fully ritualized in its expression. This view has also enjoyed a certain amount of support in the scientific literature since the publication of the classic laboratory study of Baerends and Baerrends-vanRoon (1950) on the behavior of a wide range of substratum-spawning cichlids.
The available field evidence presents a very different picture of the mechanics of pair formation in these fishes, however. Two broad patterns appear to characterize this phase of the cichlid life cycle. In the first case, one sex, usually though not invariably the male, establishes a territory from which courtship is actively directed at the other (Perrone, 1978). The courted sex makes an evaluation of the territory and its proprietor that apparently serves as a basis for deciding whether to move in or continue shopping. If the decision is to stay, the courted fish simply moved into the territory and immediately begins to share in its defense. In the second case, the prospective partners evaluate one another prior to the establishment of a breeding territory. Only after a pair bond has formed does the loving couple descend and attempt to establish its demesne, not infrequently at the expense of an already resident pair (Keenleyside and Bietz, 1981; Loiselle, 1977; McKaye, 1975, 1977). In neither case does courtship involve any behavior more overtly aggressive than low-level opercular flaring or lateral displays.
The discrepancy between the sort of behavior observed in the field and under aquarium conditions is more easily explained than might first appear. Simply put, in nature the courted sex is spatially unconstrained. What this means is that if the male and female are at different points in their reproductive cycles, they can simply separate and go their respective ways. The courting sex then resumes its activities, eventually to encounter a receptive member of the opposite sex. This option is rarely available to cichlids under aquarium conditions. The elaborate interactions that occur between male and female cichlids in captivity arise precisely because the individuals in question are maintained in enforced proximity. Such an arrangement invariably elicits a certain amount of aggression, the male usually taking the initiative in most species. If all goes as the breeder hopes, the conflict between the motivational systems underlying sexual and aggressive behavior will tilt in favor of the former as the hormonal events associated with reproduction come to assume progressively greater importance in mediating the two fishes' reactions to one another. The result is coexistence for the interval required to spawn and rear a brood of fry to independence. If not, the male's initial tendency to respond aggressively towards the female goes uninhibited. Barring the timely intervention of their keeper, the end result is a severely battered or dead female. The likelihood of successful pairing and the stability of such pairs after they are formed vary from one cichlid species to the next, but for no species in captivity is the risk of lethal intersexual violence totally absent from the preliminaries to spawning.
Given such a situation, how can the cichlid hobbyist so arrange matters that the end result of his breeding efforts is matrimony rather than mayhem? Conventional wisdom dictates purchasing six to twelve juveniles of a given species and raising them to sexual maturity together in a large aquarium. Pair formation typically occurs freely under such circumstances. The usual explanation given for this state of affairs is that the fish have a wider selection of potential partners under such a regime and are thus more likely to make a happy choice in the mating game. As is often the case with conventional wisdom, the phenomenon in question is real but the explanation offered for it dangerously flawed. Its fallacy is demonstrated graphically each time that a new pair of cichlids breaks up after its transfer to a separate breeding tank or following the evacuation of its former tankmates from the rearing aquarium.
Contrary to popular belief, substratum-spawning cichlids do not behave like the dramatis personae of romantic potboilers. Male cichlids are about as selective in their approach to potential spawning partners as sailors on liberty after a year's sea duty are towards their choice of female companionship. Female cichlids, on the other hand, appear to operate on the principle of: "When I'm not near the boy I love, I love the boy whose near!" Assuming that they are at comparable points in their reproductive cycles, any set of male and female conspecifics appears as likely to pair successfully as any other set of potential partners drawn from the same population, given the same environmental conditions.
If this is so, why then does pair formation occur more readily and reliably in a group situation? Bear in mind that for pairing to occur, the two individuals in question must both have their reproductive cycles in synchrony as well as find some way of mediating the conflict between sexual and aggressive behavior in a manner that favors the former. Rearing a group of potential breeders together enormously increases the likelihood that male and female cycles will be in sync simply by providing both sexes with an identical environment. Not only do the two sexes experience identical ambient conditions, but synchrony is further promoted by the potential for constant exchange of subtle chemical cues between males and females well before the onset of actual courtship. So just by having the two sexes together in the same tank, one automatically satisfies a necessary precondition for successful pair formation by promoting reproductive synchrony' between males and females.
Secondly, by providing precisely the target fish most likely to elicit a strong aggressive response, namely conspecifics of the same sex, the community approach goes far towards minimizing the amount of aggression the potential partners will direct towards one another. To a certain extent, such an arrangement duplicates the conditions prevailing in nature, where breeding sites are often in short supply. Under conditions, it is not at all uncommon to see pairs defending their territories, male facing off against intruding male, female against female. When this pattern is allowed to repeat itself in captivity, successful pairing is virtually guaranteed. To somewhat oversimplify matters, the two fish direct the aggression their mutual proximity elicits outwards, towards the conspecifics sharing their tank, rather than inwards, towards one another. This in turn facilitates the shift toward sexual behavior in their reciprocal interactions.
Thus the ideal case. However, there are circumstances under which the group rearing approach is impractical. It is obviously difficult to implement when very large cichlids such as the guapotes are involved. Rearing six to eight Cichlasoma managuense or Petenia splendida to maturity under such conditions entails far larger tanks than the average aquarist can usually come by. In other cases, economic considerations or other factors, which limit the number of animals available for a breeding effort, make this option impractical. There are few hobbyists who can afford to purchase such species as Lamprologus sexfasciatus or Tilapia buettikoferi in dozen lots at their current prices. Finally the group rearing approach raises the problem of what to do about the remaining individuals once the pair has formed.
In many instances, this last question is rendered moot by the behavior of the first pair to form. The Tanganyikan Lamprologus and their allies seem particularly given to this sort of intramural thugee. Indeed, their approach to courtship seems to be something on the order of: "Hello! I'm a boy (girl) and you're a girl (boy). Let's kill everyone else in the tank and make babies!" There are always humane and not infrequently economic objections to allowing such behavior to run its course. Yet if it does not one is faced with the twin difficulties of furnishing the target fish necessary to keep the pair bonded for the course of a reproductive episode on one hand and disposing of four to ten suddenly otiose cichlids on the other. The latter task tends to fall in difficulty somewhere between that of finding homes for an unexpected litter of kittens and selling Iranian war bonds at a Veterans of Foreign Wars convention!
The problem of disposing of surplus specimens can be avoided if one allows a male and female to interact in a community situation. Under such conditions, heterospecifics act as the targets for the incipient pair's aggression. Assuming that all the fish present are comparably belligerent, such an arrangement will usually facilitate pair formation in much the same manner as the group rearing approach for the majority of substratum-spawning cichlids. The problem of what will happen to the happy couple's neighbors still remains, however. 1n general, those species which do not pose a serious threat to the continued well-being of their companions are unlikely to pull off a successful spawning in their presence, while those that can breed successfully in a community situation can be trusted not to eradicate its other inhabitants only in very large tanks.
What is called for is an approach to pairing up such cichlids that affords the aquarist the confidence of success characteristic of the group rearing or community approach, yet that does not commit him to re-enacting the aquaristic counterpart of the Texas chainsaw massacre. The simplest way out of this quandary is to partition off the portion of the community tank the pair has begun to defend with a transparent barrier. As long as they can see the target fish, the two mates will continue to interact benignly with one another while persisting in their efforts to thrash their suddenly inaccessible neighbors. An equally workable and possibly more practical variant of this tactic is to partition off a separate breeding tank. The newly formed pair is moved into one compartment, the appropriate target fish into the other. Such an approach seems to work particularly well if one has two conspecific pairs separated from one another in this fashion. The essential point to be made is that the target fish must be clearly in view of the pair on a regular basis. Hence the barrier must never be allowed to grow opaque due to algal growth. Inattention to this detail of maintenance can result in a tragedy even after several weeks of fruitful cohabitation by male and female. Thus by exploiting the fact that redirected aggression need not actually strike its targets to promote coexistence of a male and female, the aquarist can reap the benefits of a naturalistic approach to pairing while avoiding its most obvious disadvantages.
There do arise circumstances where prudence forbids allowing the male and female to ever come into physical contact. Attempts to pair off fully grown adults of very large species such as C. dovii or of smaller but extremely aggressive species such as Hemichromis elongatus or C. zaliosum fall into this category. Nor does the prudent aquarist willingly risk the only available pair of a newly imported species, regardless of its reputation for prespawning docility or marital stability.
Fortunately there is an approach to breeding substratum-spawning cichlids that eliminates all risk of injury to the pair while assuring their keeper of an acceptable number of fry. The incomplete divider technique, developed by Guy D. Jordan and his coterie of pioneering guapote fanciers in the mid 1960's, exploits an essential feature of external fertilization, the tendency for spermatozoa to diffuse throughout an aqueous medium. 1n its simplest version, this technique entails dividing the breeding tank with a glass partition whose lower surface is prevented from coming into contact with the floor of the aquarium, leaving a crack through which the breeders cannot pass. A suitable spawning site is placed immediately adjacent to the barrier on that side into which the female will be introduced, then the prospective parents are placed in their new quarters.
The pair will interact through the divider, their activities climaxing in the female spawning on the site provided for that purpose. The male will in the meantime exercise his function on the other side of the barrier. Sufficient milt will pass under the barrier to assure fertilization of a significant fraction of the newly deposited eggs. The actual percentage will depend upon how efficiently and rapidly the tank's filter circulates its contents, upon the distance of the spawning site from the barrier and upon its permeability. In its most rudimentary form, the incomplete divider method will result in fertilization of 50% to 75% of a clutch of eggs. For very prolific cichlids, such as most of the larger , this usually represents a more than adequate return on the aquarist's efforts. Higher percentages of fertilized eggs will result if the fish are separated by a barrier that is more fully permeable to the passage of spermatozoa. Plastic screening fastened to a rigid frame or egg crate diffuser sheeting cut to fit the interior dimensions of the breeding tank will serve this purpose nicely and are easily procured in the bargain.
Using, this approach, the aquarist still can benefit from the complex hygienic behavior that makes cichlids as a group so easily reared under aquarium conditions, for the female will tend her clutch with the same efficiency as she would under conditions of free interaction with her mate. An additional advantage of the incomplete divider method is that it allows both parents to become involved with the care of the mobile fry, which can pass freely through the barrier. One can thus enjoy the sight of the fry interacting with both parents without exposing the female to the risk of serious injury or death.
As I implied earlier, spawning polygynous cichlids entails some rather different approaches, which I will explore in a subsequent essay. The novice cichlid breeder who makes use of the techniques related above should find himself a competent cichlid matchmaker within a very short time. With the problem of successfully pairing substratum spawning cichlids thus put into proper perspective, I close with the observation that these fish cede place to no aquarium resident with regard to the fascination their reproductive biology exerts upon hobbyists or with regard to the ease with which they can be bred.
- Baerends, G.P. and J.M. Baerends-vanRoon. 1950. An introduction to the study of the ethology of cichlid fishes. Behaviour suppl. (1): 1 - 243.
- Innes, W. 1938. Exotic Aquarium Fishes. Third Edition. Innes Publishing Co. Philadelphia.
- Keenleyside, M.H.A, and B.F. Bietz. 1981. The reproductive behaviour of Aequidens vittatus (Pisces, Cichlidae) in Suriname, South America. Env. Biol. Fishes 6: 87 - 94.
- Loiselle, P.V. 1977. Colonial breeding by an African substratum-spawning cichlid fish, Tilapia zillii (Gervais). Biol. Behav. 2: 129 - 142.
- McKaye, K.R. 1975. Some aspects of the biology and behavior of the cichlid fishes of Lake Jiloa, Nicaragua. PhD Thesis, University of Califomia, Berkeley, pp 1 - 137.
- McKaye, K.R. l977. Competition for breeding sites between the cichlid fishes of Lake Jiloa, Nicaragua. Ecology 58: 291 - 302.
- Perrone 1978. Male size and breeding success in a monogamous cichlid fish. Env. Biol. Fishes 3: 193 - 201.
- Sterba, 1966. Freshwater Fishes of the World. Revised English language edition. Studio Vista Ltd., London.