Scientists study spawning Cichla
Scientists have studied the reproduction of one of the world's largest cichlid species - the tucanare, Cichla aff. monoculus.
Munoz, van Damme and Duponchelle studied the breeding behaviour and distribution of a form of Cichla they refer to as Cicla aff. monoculus, which occurs in the waters of the Rio Paragua in Bolivia, South America.
The study found that the cichlid was most common in the smaller remnant channels, rather than the main river itself, as well as in isolated lakes. The specimens in the main river spawned a month later than those fish living in the channels or lakes, and also constructed different shaped nests. The fish in the isolated lakes dug deeper, larger nests than the fish living in the river or its channels. Brood sizes in the species are vast with 460g females producing on average 3712 eggs per spawning, and larger females weighing in at 1.38kg laying 10,355 on average.
Nest buildingThe study provides an interesting insight into the reproduction of the fish, which may be of use to any fishkeepers attempting to spawn the species. Both male and female were involved in the digging of the nesting pit and the cleaning of the ground to remove organic matter from the spawning site. Cichla aff. monoculus constructs a large circular nest just under 2m/6'6" in diameter, which contains a central depression of 20-100cm/10-39" deep.
Cichla aff. monoculus seems to prefer building its nest around branches or sticks that protrude from the substrate. Out of 291 nests examined, a massive 279 of them were dug around a slender branch with a diameter of 3-30cm/1.5-12" which was usually buried in the substrate at one end.
During the breeding season, the fish breeds in close proximity to other Cichla, and a 50m2 area can contain as many as 18 nests, usually separated from each other by a metre or so of no-man's land. The species also has a penchant for deeper water, and does not spawn in water less than 1m/39" deep.
SpawningAfter the pair had constructed their nest, the female laid up to 10,000 eggs on the branch, often covering it completely if the branch was relatively small. Both parents defend the nest when an intruder comes within 2m/6'6" of the spawning site. Although both sexes would leave the nest to defend the clutch, she was always the last to leave the eggs and was always the first to return to the brood.
The authors state that as soon as the female leaves the nest, small tetras of the characid family rush in and try to steal the brood, but quickly disperse when she returns.
After the eggs hatched, the fry stayed within the deep part of the nests below the branch, where they swam under the close supervision of their parents.
Like other members of the Cichla genus, aff. monoculus shows sexual dimorphism, with males reaching a large size and developing a nuchal hump which is not usually seen in females, except on rare occasions.
How many Cichla?The taxonomy of the Cichla genus is complex and all species can be difficult to identify. There are currently five species: Cichla ocellaris, Cichla temensis, Cichla orinocensis, Cichla intermedia and Cichla monoculus.
Kullander and Nijssen (1989) suggested that the genus may contain a further six undescribed species, however, recent studies have shown that Cichla form natural hybrids in nature, and some of the fish currently regarded as new species may in fact by hybrids.
For more details on the study see the paper: Munoz H, van Damme PA, and F Duponchelle (2006) - Breeding behaviour and distribution of the tucanare Cichla aff. monoculus in a clear water river of the Bolivian Amazon. Journal of Fish Biology (2006) 69, 1018-1030.