Cichlids of Laguna de Apoyo by Willem Heijns

People are always asking what is to see in Laguna de Apoyo during a SCUBA dive. Lots of folks have Open Water certifications these days, but most of them have only dived in tropical oceans, over coral reefs where brightly colored fish dazzle. Tropical coral reefs are indeed among the best eye candy on the planet. But people are intrigued when they learn that we SCUBA dive in tropical lakes when the ocean is so close. It's obvious to them that something very attractive must be going on down there to keep our attention, with coral reefs just a couple of hours away.

We at FUNDECI/GAIA study the fish in this lake and in other freshwater locations in Nicaragua. Lake Apoyo has clear, warm water (28 degrees C) which makes it easy to view the fish underwater. Our divers have been collecting data on the fishes of Lake Apoyo for years, learning about the differences between very recently evolved species and even documenting the species themselves. Over the years, other research groups have also become interested in the cichlid fishes of Lake Apoyo and neighboring lakes, especially the group headed by Axel Meyer of the University of Konstanz.

The fish of the Midas cichlid group are definitely the main attraction in Laguna de Apoyo. Since the lake was formed some 23,000 years ago, the lake has been colonized by a few species of fish, but the dearth of species in the lake has left numerous, broad niches available for specialization in feeding, refuge behavior, and nesting activity. The Midas cichlids in the lake have undergone a remarkable evolution, dividing into numerous species. Six species from this group which are only found in Laguna de Apoyo are now accepted in the scientific community. Publications which present these six species can be found here, here, and here. These cichlids are terribly similar, but they do not interbreed, and they even use different timing and locations for nesting in the lake. 

The video presented above, produced by Willem Heijns, is among the best quality of videos showing some of these species in their natural habitat. We hope you enjoy seeing this video. Thank you, Willem!

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Under the water

We spend hundreds of hours per year under the water in Laguna de Apoyo, in counts of fish, documentation of the quality of the habitat where they live, the vegetation found there, and yes, even in retrieving the trash that folks discard which ends up all along the lake bottom. Here is a small collection of photos which show what we see when we are down there, in the most beautiful spot in Nicaragua. In the photoessay below, you can experience what one of our interns saw during a study of the fish with the director of the Gaia Program, Dr. Jeffrey McCrary. Dr. McCrary is leading an international team in the study of the fishes of Laguna de Apoyo, and to date five new species have been discovered as part of the program. 

These fry of an Amphilophus zaliosus pair recently hatched in a nest hole which is often seen with babies. 

Lots of fish are hanging out in this site, including a probable male Amphilophus zaliosus in breeding coloration in the center of the photo. 

Counting fish along a transect.

Juveniles and nonbreeding adult Amphilophus seek refuge under rocks in Laguna de Apoyo.

Breeding season is approaching, and breeding pairs are forming. A pair of Amphilophus zaliosus are in the foreground, and a pair of jaguar cichlids, Parachromis managuensis, are in the background. 

As can be seen from the photos, several Midas cichlid species are locally abundant in the waters of Laguna de Apoyo. Of the six species recognized in Laguna de Apoyo in this group, the most abundant of the group in most locations is the little Apoyo cichlid, Amphilophus astorquii. Other fish species are in the lake, too: Atherinella sardina, Poecilia sphenops, and Parachromis managuensis, as well as some invasive species.

Fish ahead!

A multispecies school of Amphilophus cichlids.

The species of Amphilophus cichlids in Laguna de Apoyo vary by body shape, spot pattern, and background colors. 

Dozens of cichlids are always under this rock!

Much of the lake bottom is covered with recently eroded sediments which cover the rocks and destroy all the high-quality habitat. Furthermore, ordinary garbage accumulates along our transects, such as this plastic cup, sold by the local bars. 

In some areas where waves clean the substrate, the lake bottom is covered with fine mud or sand. 

Fragments of snail shells (Pyrgophorus coronatus) litter the surface in many places. Snails are an important component of the diets of the Amphilophus species flock in Laguna de Apoyo. 

Filamentous algae has displaced Chara vegetation along the bottom in much of the lake. We do not understand why Chara often disappears from the lake, although it is known that tilapia will consume large quantities of it. 

In shallow areas with small rocks, juveniles of the invasive species Gobiomorus dormitor abound. 

Many shallow areas are covered with snail shell fragments, demonstrating the abundance of snails in Laguna de Apoyo.

A human-altered waterscape in Laguna de Apoyo. Filamentous algae and a plastic beverage bottle displace native fish and vegetation. 

Silversides, Atherinella sardina, put on a show in the water column. Silverside schools may exceed ten thousand individuals. 

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SCUBA diving in Lake Apoyo, Nicaragua

Hundreds of young arrow cichlids (Amphilophus zaliosus) are only perhaps sixty days from hatching. Although they have been abandoned by their parents, they continue to school at a nesting site. Photo by Martin Cabrera.

We often get asked what can be seen while SCUBA diving in Laguna de Apoyo. Nicaragua has lots of lakes and rives, but most tropical freshwater sites here and elsewhere have low visibility. Lake Apoyo visibility is almost always 5-12 meters at the locations where we dive.

The fish of Lake Apoyo are special, too. The most commonly seen fish are members of the Midas cichlid species complex. Six species in this group have been discovered  in Lake Apoyo, all of which evolved in the lake and inhabit only this lake. The first to be discovered was the arrow cichlid (Amphilophus zaliosus) in 1976 by a professor at University of California-Berkeley, George W. Barlow. Most of these six endemic species can be seen while scuba diving.

Arrow cichlids, like all the other members of the Midas cichlid species complex in Lake Apoyo, nest in rocky reefs, but they also nest often over sandy bottoms in water from 4 to 8 m depth. All the fish in this species complex, which is found throughout the San Juan River watershed and a few rivers to the north and south, provide parental care to their fry for several weeks after hatching. Here is a photo of the arrow cichlid fry after the parents have abandoned them. These fish are no longer defended from predation by the parental units. 

These arrow cichlids have not yet dispersed but are no longer receiving parental care. Photo by Martin Cabrera. 

The parental units expend a lot of energy during the seven weeks of care of the fry. Predators constantly attempt to capture the small fish and they are fended off by the parental units. It's a long seven weeks, not including the courtship and egg-incubation. Parental units often look battered and even emaciated at the end of the period of parental care. However, the great majority of nests never make it to seven weeks fry age, because predation and disease will have killed of the entirety of their nests.

After a scuba dive in Laguna de Apoyo, the clearest lake in Nicaragua. Photo by Martin Cabrera.

Lake Apoyo is the easiest of all locations for scuba diving in Nicaragua. We are located only one hour from downtown Managua. Estacion Biologica collects data at four sites in Laguna de Apoyo, all have easy reach from the shore, and great views below. We enter our study areas from the shore, along property managed by Estacion Biologica.

Life is good after a dive. Photo by Martin Cabrera.

One vital reason for our monitoring program is the bigmouth sleeper, Gobiomorus dormitor. This fish looks a lot like a goby, only much larger as an adult. This voracious predator sits quietly on the lake bottom, where it awaits an injudicious move by any appropriately sized fish, when it strikes with lightning speed. The fish of Lake Apoyo spent thousands of years without the threat of bigmouth sleepers or anything similar, so they are now evolutionarily naive to the grave threats this fish presents.

The Bigmouth Sleeper (Gobiomorus dormitor) is a dangerous predator. It was introduced into Lake Apoyo in 1991. Photo by Martin Cabrera. 

Bright blotches, usually randomly placed, are not exactly uncommon among fish. These colors are usually caused by a specific mutation, such as in the goldfish, which is simply a selectively bred variant of a wild carp. Midas cichlids have a similarly brightly colored variation in the wild, although the "golds" are much more common in some locations than in others. Lake Apoyo, for instance, is considered to have no gold forms. Nonetheless, as the photo below demonstrates, gold forms may also be found in Lake Apoyo.

Gold form Midas cichlids are relatively common in some lakes, but not in Lake Apoyo. Fish such as the one in this photo are exceedingly rare. Photo by Martin Cabrera. 

Which gene(s) control the gold color form in the Midas cichlids is not known. Nor does anyone understand why Lake Apoyo has so few golds. In comparison to most other natural habitats of the Midas cichlids, Lake Apoyo has far fewer golds.

Some Midas cichlids show 

This clownish coloration is quite common among Midas cichlids in Lake Managua, some parts of Lake Nicaragua, and other volcanic crater lakes such as Lake Masaya and Lake Xiloa. Why is it so rare in Lake Apoyo? We don't know.

This breeding, gold form Midas cichlid stays near the nesting hole. Photo by Martin Cabrera.

Midas cichlids are territorial when nesting. A breeding pair will occupy a natural or constructed hole, often at the base of rocks, in which a hard, flat, usually vertical surface can be utilized to adhere eggs. The pair will defend the site vigorously against predators and usurpers.

The gold-normal breeding pair linger near the nesting cavity. Photo by Martin Cabrera. 

The great majority of Midas cichlid nests do not result in the eventual creation of new adults. Hundreds of eggs are produced in each spawning, but very few fry will reach the age to swim away from the parental units and begin life independently of them.

The Bigmouth Sleeper has occupied Lake Apoyo only two decades, but is now very common. Photo by Martin Cabrera.

The newest reason for the demise of nests in Lake Apoyo, the bigmouth sleeper, has become very common in the lake. Some of the Midas cichlid species of Lake Apoyo are so rare that the bigmouth sleeper could even make the species disappear. Who would even know if a fish species in Lake Apoyo went extinct?

Filamentous algae forms a carpet on the lake bottom where Chara macroalgae was once abundant, placing much of the life in the lake at risk. Photo by Martin Cabrera. 

The bigmouth sleeper has a neutrally colored, mottled pattern along its sides and back, making its detection difficult. It sits on the bottom, awaiting a false move by some other fish. It strikes rapidly, with the intention to sink its long, fine teeth into the prey and then gradually move the prey into the mouth to swallow it.

A Bigmouth Sleeper (Gobiomorus dormitor) pair in courtship in Laguna de Apoyo. Photo by Martin Cabrera. 

The success of bigmouth sleeper (Gobiomorus dormitor) during the two decades of its time in Lake Apoyo is startling. They are extremely common. Recent research conducted by Topi Lehtonen and the research team at FUNDECI/GAIA demonstrated that the Midas cichlids of Lake Apoyo do not recognize the threat these fish present to their fry.

These Midas cichlid fry must share their nest space with garbage left by humans. Photo by Martin Cabrera.

Lake Apoyo's fish species are facing several threats from humans. Soil introduction into the lake is higher than ever, coming from constructions in the watershed. Predation and loss of habitat by introduced species have done lots of damage to the species found here. And of course, garbage follows humans everywhere we go. The fish of Lake Apoyo have no choice but to utilize garbage-filled areas of the lake to feed and reproduce.

Juvenile Amphilophus cichlids in Lake Apoyo, Nicaragua. Photo by Martin Cabrera. 

Lots of juvenile Midas cichlids are present year-round in Lake Apoyo. By diving during the different seasons, one can see the smaller fish grow and, by the end of about a year, start their first anniversary as members of the next breeding stock. The intense uses (and misuses) of Lake Apoyo by human beings requires that we assure adequate habitat for these fishes in all their life stages.

A blind Amphilophus astorquii in Lake Apoyo, Nicaragua. Photo by Martin Cabrera.

To date, six species of the Midas cichlid species complex have been described in Lake Apoyo. All of them are only found in this lake. There are eight volcanic crater lakes such as Lake Apoyo, near the Nicaraguan Great Lakes, which have multiple species of Midas cichlids in them. What was once thought to be only one or a few species is now considered to be dozens of species, with very small ranges, and in some cases, populations of only a few thousands of adults. One of those species with a very small population is the chancho cichlid, Amphilophus chancho. It is the largest of the Midas cichlid species complex found in Lake Apoyo, with males sometimes reaching well over a kilogram weight.

Amphilophus chancho defending fry in a nesting hole in Lake Apoyo. Photo by Martin Cabrera. 

Child-rearing is an expensive venture for most species. It is especially so for the Midas cichlid species of Lake Apoyo, too. Providing care for the fry means eating less and lower quality food. It also means getting in harm's way. The parental units must confront potential predators and utilize displays, threats, and if nothing else works, direct attacks to drive away the fish and crabs that would want to eat the fry. Adults often look emaciated and battered at the end of the breeding season.

Amphilophus fishes near a hole beneath a rock in Lake Apoyo, Nicaragua. Photo by Martin Cabrera.

A scuba dive with the staff at FUNDECI/GAIA usually means seeing most of the six species of the Midas cichlid species complex, perhaps about five hundred individuals in total. Occasionally, we get to see jaguar cichlids (Parachromis managuensis) up close, while nesting. It also means seeing the ubiquitous bigmouth sleeper, lots of them, perhaps upward of a hundred individuals in a single dive. Other fish, crabs, and the dramatic undwater views round out most dives. Some of the dives take you to thermal vents, where clear, warm water flows from between rocks into the lake. And especially during the appropriate season (November through February), lots of fry in nests!

An adult bigmouth sleeper uses a hole beneath a rock as a hiding spot, from which to hunt. Photo by Martin Cabrera.

Diving in Lake Apoyo is different than in the ocean and generally much easier. No currents, waves, poisonous animals produce dangers here. The dives are rewarding and especially so when contemplating the rarity of some of the fishes, to which our divers contribute to study and protect them. Please contact us if you would like to dive with us in Lake Apoyo.

Jaguar cichlid (Parachromis managuensis) fry are feeding in open water outside their nest cavity in Lake Apoyo, Nicaragua. A small clump of Chara vegetation can be seen in the lower left. 

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Amphilophus chancho

The Midas cichlid (Amphilophus) species flock is composed of several species, and the research group at Estacion Biologica has been working on describing new species in the group. The largest of the Midas cichlid complex found in Laguna de Apoyo is the mojarra chancho, Amphilophus chancho Stauffer, McCrary & Black 2008. It is named after the Nicaraguan local name for pig, for its corpulent appearance.

Mojarra chancho in breeding coloration. Photo by Adrianus Konings.

Like other Midas cichlids in Nicaragua, the mojarra chancho find mates near breeding areas, then establish a breeding site with a natural or dug hole. They usually make nests at between 12 and 25 meters depth, in areas of massive nesting. The parents are sequentially monogamous, with both male and female staying on nest to care for the fry around forty days after free-swimming.

Juvenile mojarra chancho. Photo by Adrianus Konings.

 The mojarra chancho can be as large as the large-mouthed predator in the lake, the jaguar cichlid (Parachromis managuensis). Its only habitat is Lake Apoyo, Nicaragua, where it evolved sympatrically with a least five other members of the Midas cichlid species complex. This species is distinctive among the crater lake cichlids for its size and behavior: notice two of the fishes in the photo below, looking at the photographer with both eyes!

Schooling mojarra chancho maraud in search of prey. Photo by Adrianus Konings.

Breeding is common from November through March. When not breeding, the fish may form monospecific schools and maraud the lake for prey. One of their most notable prey is the eyes of fish that have become blind by cataracts.
The conservation status of Amphilophus chancho has not been evaluated, but we expect it to receive status as an endangered species, given that its range and population are similar to those of the arrow cichlid, Amphilophus zaliosus, which has recently been declared Critically Endangered.

Mojarra chancho female with fry. Photo by Adrianus Konings.

Our SCUBA diving program has helped us determine that this is indeed a distinct species and to develop information about its ecology. We see several individuals each time we dive, and nests are not uncommon during the height of nesting season. By diving with us, you get to see some of the most interesting of animals in Nicaragua, in the water! If you are a certified open water diver, you can participate in a dive with us and help us learn more about the endemic fish species in Lake Apoyo. For more information on how to help us study this fascinating fish, please contact us.

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Sympatric Speciation Demonstrated Among the Midas Cichlid Species Complex

The Midas cichlid, Amphilophus citrinellus, was once thought to extend throughout the entirety of the San Juan River basin, including throughout both the Nicaraguan Great Lakes and many volcanic crater lakes along their western shores, habitat that only includes the southern half of Nicaragua and the northern half of Costa Rica. Thanks to work published by our research group in the past several years, two crater lakes are known to have multiple species, each endemic to its respective lake. More recently we have studied chromosomal and mitochondrial DNA profiles among the Midas cichlid forms found throughout much of its range, in which we found that each volcanic crater lake has its own group of species, suggesting dozens of species among this group yet to be discovered. Matthias Geiger, Jeffrey McCrary and Uli Schliewen demonstrated and interpreted the DNA profiles in "Not a simple case – A first comprehensive phylogenetic hypothesis for the Midas cichlid complex in Nicaragua (Teleostei: Cichlidae: Amphilophus)" in Molecular Phylogenetics and Evolution. This article confirms our suspicion, that the Midas cichlid species complex consists of dozens of species not yet discovered, in addition to the eleven currently recognized species.

Each isolated stock of Midas cichlids, particularly those in volcanic crater lakes, formed its own species flock by sympatric speciation. The inhabitants of each lake are evolutionarily closer to each other, than to any of the Midas cichlids in any of the other bodies of water.

Amphilophus astorquii pair with fry in Lake Apoyo, Nicaragua. Photo by Ad Konings.

The implications of the publication mentioned above include that each lake harbors its own set of species in the Midas cichlid complex, and that those species are likely not shared among lakes. The ranges of each fish species are very limited, meaning threats to their populations can be very high. One species from this group, the arrow cichlid (Amphilophus zaliosus), has been classified as Critically Endangered on the IUCN Red List. By extrapolation, we can expect many species to be ranked as Endangered or Critically Endangered when their conservation status is finally evaluated.

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Video: Endemic Fish Species in Laguna de Apoyo, Nicaragua, Threatened by Humans

The volcanic crater lakes of Nicaragua attract lots of tourists, both Nicaraguans and foreigners. The water-filled craters are all beautiful, each with its own special features. Eight of these lakes, however, have endemic fish species, daughter species of the ancestral form of the Midas cichlid (Amphilophus citrinellus), living in them. The water of most of these lakes is transparent, perfect for observing these fish while SCUBA diving.

During the nineteenth century, scientists and explorers admired the wide variations in color and shape among the Midas cichlid group, so much so that several species were described during the succeeding fifty years. Most of those species are today lumped back into A. citrinellus, given that this is the first described of the group from Lake Nicaragua. Its sister group, A. labiatus, has similar features but is generally longer and sleeker bodied with prominent lips and frenum. This fish became incorporated into the aquarium hobby trade in a brightly colored form, and is still known as the red-devil cichlid. Only these two species "survived" the scientific scrutiny of the first three-quarters of the twentieth century.



Amphilophus labiatus showing its prominent lips in Laguna de Xiloa, Nicaragua. Photo by Ad Konings.

People knew these fish populated not only the Nicaraguan Great Lakes, but also the volcanic crater lakes along their western shores. The late, visionary scientist George Barlow applied for the first time, multivariate analysis to the morphological characters of fish populations in this group to demonstrate convincingly that A. labiatus and A. citrinellus were different species, and that in Lake Apoyo, a unique species exists as well, which he called the arrow cichlid (Amphilophus zaliosus). This species, more elongate than A. citrinellus and lacking the fat lips of A. labiatus, was found in Lake Apoyo. 

A pair of Amphilophus zaliosus on nest, in breeding coloration. Photo by Ad Konings.

The sacred trinity of A. citrinellus, A. labiatus, and A. zaliosus stood through the remainder of the twentieth century. During the current century, we incorporated the talents of Jay R. Stauffer, Jr. in the taxonomic descriptions of fishes in this group. To date, he has led the descriptions of eight additional species-three from Lake Xiloa, and five from Lake Apoyo, Nicaragua. They will be discussed in a coming blog entry. Most of the species from Lake Apoyo can be appreciated in the video below.

Video by Balasz Lerner.

This second video, produced by Fabio Buitrago, shows underwater footage of endemic fish species in Lake Apoyo, facing a crisis of man-made dimensions-garbage. Everywhere. Why must we pollute their home? These fish-six species known and others not yet discovered-only live here in this lake.

The most common of the fish in this video, and in just about any part of the lake where we have looked, is the little Apoyo cichlid, A. astorquii. It was named in honor of Father Ignacio Astorqui, a Jesuit priest from Spain who devoted much of his life to the study of freshwater fishes of Nicaragua, and wrote the first comprehensive guide to them. A breeding pair with their fry are shown below:



Amphilophus astorquii pair caring for fry, Laguna de Apoyo, Nicaragua. Photos taken during scuba diving by Adrianus Konings.

Would you like to help us protect and study the endemic cichlid species of Laguna de Apoyo? One of these species is already on the endangered list (Arrow cichlid, Amphilophus zaliosus, Critically Endangered-IUCN). Nicaragua needs your help, because the threats are many, and resources are few. We are seeking divers, biologists, people with experience in excel, and volunteers without any specialized skills to help us in this project. Please contact us if you would like to participate. The Laguna de Apoyo Spanish School also supports this project by providing a portion of its proceeds to fund our studies and conservation efforts. Would you like to learn Spanish? Think about attending our program, and go diving with us, too!