Nesting For Success

The sight of a new cichlid nest in an aquarium brings both excitement and trepidation to the cichlid aquarist. Along with the prospect of dozens, hundreds or even thousands of fry comes the possibility of injuries or death to tankmates of the breeding pair.

Breeding is serious business for cichlids. Mortality rates in the wild can be extraordinary with many nests succumbing each day to seemingly tireless predators. For example, of 87 spawnings of Neolamprologus mondabu in Lake Tanganyika, Takemon and Nakanishi (1998) found that the total brood was lost in 68 cases! So it isn't surprising that the cichlids we keep in our aquariums also take breeding very seriously, and as a result, we observe elaborate displays, digging and fighting off potential nest predators. Understanding the function of nests in the wild gives us greater insight into what is going on in our tanks.

Cichlid nests vary in size and appearance from a simple clearing on the substrate to the elaborate tunnel nests of Hypsophrys nicaraguensis (Coleman 1999). Some cichlids take advantage of natural concavities, like many Archocentrus species, and others use specific objects, like abandoned snail shells, as is commonly seen in Lake Tanganyika.

I use the term "nest" to describe a place not only for spawning but also for taking care of the eggs and/or larvae. Most mouthbrooders do not make nests. McKaye et al. (1990) have argued that the spawning structures made by mouthbrooders in Lake Malawi are best described as "bowers," not nests, in reference to their similarity to the bowers made by certain nesting birds. A bower is a structure built for the express purpose of attracting a mate, not for rearing young. Just because bowers are not nests doesn't mean they aren't important - far from it - these structures convey vital species-specific information, as well as information about the quality of the male that built the bower. Females are highly attuned to distinguish between excellent and mediocre bowers and choose their spawning partners accordingly.

Like bowers, nests also serve as a site for mate attraction and many fishes put substantial effort into nest preparation, creating structures that are not only beneficial for the future offspring but also demonstrate to potential partners the skill, quality, and attention to detail of the nest constructor.

We actually know remarkably little about nest construction for many cichlids. Many nests are often difficult to detect until they are well on their way toward completion. For example, many aquarists only notice a nest either just before or after spawning has occurred. Nest construction can be very rapid in cichlids. In Central American cichlids, parents may need as little as a few hours. In the wild I typically observe a pair of fish hanging around a particular spot and by the next day they have laid eggs. Important questions are unanswered: does one fish choose the nest site, start the nest and then attract a partner, or does the pair form first then together find a site and begin a nest? There is no reason to believe that the answer will be the same for different species.

The principle function of a nest is to provide a safe environment for the eggs and possibly the larvae. Achieving this usually requires modifying the existing terrain, including cleaning it, digging into it, and removing vegetation.

The first sign of nesting is often a parent, typically a female, pecking repeatedly at a hard surface, like a rock or piece of wood. If these are in short supply, many cichlids will dig to find something solid. Several years ago I studied Texas cichlids in the San Marcos River, Texas. This river is a spring-fed, constant temperature stream found in South Central Texas and is home to a long-established introduced population of Texas cichlids (Herichthys cyanoguttatus), and incidentally a great spot to go snorkeling to see cichlids doing their thing in the wild.

In the San Marcos River in Texas, adult Herichthys cyanoguttatus clear vegetation from steep banks for nesting purposes. Photo by Ron Coleman.

The cichlids spawn along the banks, under the over-hanging vegetation. The sandy substrate is covered in aquatic plants over much of the spawning area. The first job of the cichlids is to remove nearby plants (much as they do in an aquarium). The purpose of removing the vegetation is not just to annoy the aquarist: it is to create a vital "clear-zone" around the nest. The parents remain in this clear-zone and watch the perimeter for potential attackers.

By making a large clear zone, the parents increase the odds of seeing potential nest predators before they can strike. In the New World, these nest predators consist of juvenile cichlids, characins, sleeper gobies, and other small species that hang out waiting for the opportunity to dash into the nest and grab a mouthful of eggs or wrigglers.

These predators are numerous, small, relentless and frequently attack in groups, leaving the parents reeling as they try to chase one after another intruder. In some cases, the onslaught is so great that the parents are overwhelmed and abandon the nest. The entire nest contents may be consumed in a minute or less. So, when your cichlids start uprooting plants, you might have a little sympathy. You may know that there are no nest predators in the tank, but parental cichlids must always be on guard.

Interestingly, some cichlids do not clear vegetation. For example, Archocentrus septemfasciatus in the Rio Puerto Viejo in Costa Rica, where I have observed them, do not appear to clear the area around the nest. In fact this fish prefers to nest under the tangled roots of trees and among leaf litter. These are the smallest cichlids in the river, and my guess is that they are trying to draw as little attention to the nest as possible. An area cleared of debris would be a giveaway to a potential predator, and the A. septemfasciatus parents would be easily overwhelmed.

Once the vegetation is cleared, almost all substrate-spawning cichlids require a solid surface on which to lay their eggs. Some species, such as some of the delayed mouthbrooders of South America, lay their eggs on dead leaves, but most cichlids are looking for a rock or a log. I was fascinated to watch the Texas cichlids excavate in search of a hard surface.

I don't know if they have some way of detecting solid surfaces under the sand, but inevitably the fish I watched would discover a rock or buried log in their cleared territory. Sometimes they had to dig almost a foot down to find it, but find it they did. The eggs were then laid on that hard surface.

Understanding why cichlids dig (though some also dig as a regular part of feeding, e.g., eartheaters and some members of Thorichthys and Astatheros) may ease the pain of finding your carefully arranged aquarium entirely re-landscaped. I suggest that if your cichlids are digging, then you haven't provided them with a large enough solid surface on which to lay their eggs and they are determined to find one. The number of eggs laid by a female does not appear to be limited by the size of the surface; instead, the female lays a predetermined number of eggs and finds a surface suitably large to accommodate them. If the rock is a bit small, the female will lay the eggs very compactly. Larger surfaces allow the eggs to be more spread out. Substrate-spawning cichlids almost never lay eggs on top of each other, because to do so would deprive the underlying eggs of oxygen.

Breeding pair of Herichthys minckleyi in Poza de la Becerra (Type locality of the species), Cuatro Ciénegas; Coahuila [Mexico] showing the male and female in their distinctive color forms and in their typical breeding caves. Foto di Juan Miguel Artigas Azas. determinatore Juan Miguel Artigas Azas

A few recent discoveries about cichlid nests suggest that even more complex interactions are occurring. Ochi and Yanagisawa (1999) recently described "sand-transfer" behavior by Neolamprologus caudopunctatus, in Lake Tanganyika. This fish constructs its nest among the stones in the lake, leaving a slit-like entrance to the nest chamber. The researchers found that during the period of egg and wriggler care, which lasted about 40 days, females often removed mouthfuls of sand from within the nest. This isn't surprising. In addition, females (and rarely males) sometimes brought mouthfuls of sand from the area around the nest to the nest entrance in an apparent attempt to keep the entrance narrow. "Kribensis" are known to do this in aquariums: if the cave entrance is too wide, they may "back-fill" the gravel until the opening is just wide enough for the female to get in and out.

The researchers also found that males and females unexpectedly transferred many mouthfuls of sand around the territory, typically depositing the sand at the base of stones. The parents were not feeding and only did this before the fry became independent. The exact reason for this behavior is not known, but Ochi and Yanagisawa propose a fascinating hypothesis. Just as with the Central American cichlids described earlier, parents of this species are vigilant toward predators that lurk around the perimeter of the territory and dash in to eat the young. Common predators include Telmatochromis vittatus, a stalker, which hides under or beside stones waiting for an opportunity to arise. Could it be that the parent Neolamprologus caudopunctatus are actively filling in these potential hiding places and thereby increasing the safety of their young? More work is needed, but it seems a reasonable hypothesis.

The advantages of a good nest are so great that some species take advantage of the nests of others. Lepidiolamprologus profundicola is a large piscivorous substrate-spawning cichlid, also from Lake Tanganyika. Female L. profundicola guard the nest area for about two weeks.

Cyprichromis leptosoma is an open-water, maternal mouth-brooder. You might think that these two species would have little to do with each other, but Watanabe (2000) observed schools of hundreds of juvenile Cyprichromis leptosoma hovering above L. profundicola nests. This observation is unusual because L. profundicola do not guard their fry once the fry become free-swimming; the fry swim away so there is no opportunity for the C. leptosoma fry to mingle in with the L. profundicola fry as has been observed for other species. Furthermore, under other circumstances, L. profundicola preys upon C. leptosoma. However, because the female L. profundicola keeps predators far away from her nest area, and the C. leptosoma do not prey on her young, these foreign fry gain substantial protection from the defensive perimeter the female L. profundicola creates.

These two studies illustrate the importance of nests, and no doubt future work will reveal yet more intriguing ways that cichlids nest for success.