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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Dive Laguna de Apoyo

Most tropical lakes have dark water, but a few, like Laguna de Apoyo, make for excellent SCUBA diving. This lake is sitting in a volcanic crater, formed 23,000 years ago. Our research group is busy here, studying the fishes of this lake, because something interesting happened during those years since the volcano left a huge hole in the ground, it filled with water, and the fish entered. Some of them transformed into new species, and they provide scientists with a great field location to consider how evolution occurs. We are responding to the call to study these fascinating fish, all evolved from Amphilophus citrinellus, the Midas cichlid.

Juvenile fishes leave their refuge to investigate divers in their area. Photo by Garey Knop.

Our group has discovered five new species in this group of fishes in Lake Apoyo. Adding to the list the arrow cichlid, Amphilophus zaliosus, discovered by Barlow and Munsey in 1976, and we have to date, a group of six closely related fishes with similar appearances, plus an unknown number of other fish that may also be recognized someday as unique species. Several of those fish are seen in the video below, taken by Garey Knop in one of our monitoring dives.

The fish of this special group are important for more reasons than just for having evolved recently into a rainbow of new species. The members of this species group provide very interesting parental care to their offspring, until the babies are several weeks old. We are very interested in how these special fish choose their mates, find their breeding grounds, and defend their fry. Here is another video by Garey Knop, in which a pair of arrow cichlids (Amphilophus zaliosus) are defending their fry, only three days since becoming free-swimming. The fry are difficult to see, but there are about 1200 of them, usually beneath the female (the smaller of the parents).

This breeding pair has made a nesting site in a featureless area, with filamentous algae covering the muddy/sandy substrate. The pair dug a hole about 80 cm wide to uncover a basalt rock surface where the eggs were deposited and fertilized. The nearest nest to this one was about ten meters away. Relatively few fish passed through the area, excepting the harmless Atherinella sardina (silversides). Both parents were busy, vigorously defending the fry. During our half hour watching the pair, the fry boldly approached us, and some of them fed on the skin on the photographer's hand! 

Garey feels at home underwater. Lake Apoyo does not have dangerous fish or currents. Photo by Garey Knop.

Lots of blind fish are found in Lake Apoyo. A parasite is suspected, although the eyes are removed by other fishes once the fish go blind. The epidermis of this fish has covered the orbit after the eye was extracted. This fish has several slash marks caused by other fishes in their attempts to bite the eyes. Photo by Garey Knop.

This blind fish shows the eye clouded by cataract. The opposite eye had already been eaten by other fish. Note the caudal fin missing a large piece, presumably eaten by some predator. Photo by Garey Knop. 

Crabs (Potamocarcinus nicaraguensis) are common in Lake Apoyo. Photo by Garey Knop.

In a typical monitoring dive, we see about a thousand fish. Almost every dive we see a crab.  From November through January, lots of fish are reproducing, and we can watch them provide parental care up close. Lake Apoyo has the clearest and cleanest water of any lake in Central America.

We gather data from the best perspective, watching the fish from a few meters distance. Photo by Garey Knop.

Would you like to help us study these fishes? If you are a certified open water diver, you can accompany our staff on a monitoring dive, and help us learn more about these fascinating fish to protect them better. Please let us know-we will take you on a dive.

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Dive Laguna de Apoyo

Let's get in the water! Photo by Kim Bracken.

Most people who SCUBA dive have experience in the ocean. But diving in a tropical lake is a unique experience, especially when diving in Lake Apoyo. Its water is too salty to be potable, however it is still near the buoyancy of freshwater. Lakes differ from the ocean, too, in smaller waves and currents, and fewer dangerous animals. Lake Apoyo has essentially no moving water, making the dives easily managed. No fish or other animals in Lake Apoyo sting or bite!

Lake Apoyo is not just a freshwater lake, however. It is a volcanic crater lake, occupying a huge volcanic caldera between Volcano Masaya to the north and Volcano Mombacho to the south along the string of volcanoes across the Pacific side of Nicaragua. Because the Apoyo volcano is mostly a hole, however, the lake is its most prominent feature.

Divers discuss their dive plan before heading down. Photo by Kim Bracken.

FUNDECI/GAIA coordinates SCUBA dives in Lake Apoyo, where you can accompany scientists in their study of the fishes. Each month, our divers review fish populations in several habitats, and visiting divers can join us on our dives. Divers get to see many species of fish in a single dive, and learn how these fish live, breed, and how we are working to protect them.

Not so many fish species occupy Lake Apoyo: only jaguar cichlids (Parachromis managuensis), mollies (Poecilia sphenops), silversides (Atherinella sardina), and several members of the Midas cichlid species complex (Amphilophus cf. citrinellus) are considered native. These fish populations probably got their start in Lake Apoyo by hurricanes, birds, or even the precolombian human populations that could have brought some individuals from Lake Nicaragua, just four kilometers to the east.

Several endemic fish species from the Amphilophus species flock occupy Lake Apoyo. The research group at GAIA has discovered five species to date. Photo by Balasz Lerner.

The Midas cichlid population of Lake Apoyo has attracted the attention of scientists for many years, and has been the principal cause behind the studies we pursue. In 1976, George Barlow began the current trajectory of interest in Lake Apoyo by declaring the arrow cichlid (Amphilophus zaliosus), as a new species. This lake is among the best study sites in the world for sympatric speciation among animals. 

Our group at Estación Biológica has studied these fascinating fish several years. In 2002, we published the official description of three new species in Lake Xiloa. Then in 2008, we published another set of species descriptions, giving official names to three species in Lake Apoyo. In 2010, we then followed with two more species descriptions in Lake Apoyo among the Midas cichlid species group. 

Our ecological studies in two lakes, Apoyo and Xiloa, where we have also performed several years of monitoring, are essential to the Midas cichlid species discoveries. Without being in the water, observing the fish month after month, we would never have been able to distinguish these very similar and closely related species. Our monitoring program has given us a wealth of information which is behind the species discoveries and several other new findings. 

The members of the Midas cichlid species complex found in Laguna de Apoyo are: 

Amphilophus astorquii

Amphilophus chancho

Amphilophus flaveolus

Amphilophus globosus

Amphilophus supercilius

Amphilophus zaliosus

These six species are elegantly displayed on our new Laguna de Apoyo t-shirts-please purchase one and support nature research in Laguna de Apoyo!

Among the more common fish in Lake Apoyo today is the Bigmouth Sleeper (Gobiomorus dormitor). This fish was introduced to Lake Apoyo in 1991, and its population has grown dramatically. We at GAIA are studying the impacts of this introduced fish on the native species of Lake Apoyo. Photo by Wito Lapinski. 

The fish of Lake Apoyo are not just some rare novelties. They are facing some serious threats to their continued existence. One of the threats comes from introduced, invasive fish species. On a few occasions, tilapias have been introduced, most notably, in the 1990's as part of an aquaculture experiment using the Nile tilapia (Oreochromis niloticus). This misguided, disastrous activity was conducted with the approval and participation of the Ministry of Natural Resources and the Environment during that period. At the time, tilapia was touted by some influential individuals in Nicaragua as an economic "silver bullet" which would make investors rich and would feed poor people, as a kind of pinnacle to the Blue Revolution. The issue of environmental and health impacts of improper tilapia aquaculture methods in Nicaragua was recently featured in the New York Times. Many ripostes followed, too!

In 1991, an over-enthusiastic local fisherman added to the mix in Lake Apoyo, by bringing a bucketful of bigmouth sleepers (Gobiomorus dormitor) he had just caught from another, nearby lake, to Lake Apoyo and dumping them in. A few fish quickly became thousands and today this fish is ubiquitous. The threats this fish poses to Lake Apoyo's endemic species is magnified by their loss of sensitivity to the dramatic threat the bigmouth sleepers pose to their fry. The research team at GAIA worked with scientists from Finland and Germany to demonstrate the evolutionary naivete to fry predation by the introduced bigmouth sleepers in a 2012 publication.

We also coordinate underwater lake cleanups periodically, our third one was performed in 2011. 

After collecting data, a relaxing moment by the pier is in order! Photo by Kim Bracken.

Would you like to dive with us in Lake Apoyo? We would be happy to schedule a dive with you. You must have the equivalent of an open water certification. We can provide all the equipment and you can help us in our research on these very special fish.

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The arrow cichlid faces threats from invasive species

Lake Apoyo, Nicaragua, is home to several endemic fish species of the genus Amphilophus, members of the so-called Midas cichlid species complex, as is Lake Xiloa. Evolution may have affected the fish in these two lakes differently, however, particularly because those from Lake Xiloa evolved in the presence of an important predator of cichlid fry, the bigmouth sleeper (Gobiomorus dormitor), whereas this predator was not present in Lake Apoyo during the two hundred or so centuries during which the several species of Lake Apoyo took form. The bigmouth sleeper was introduced into Lake Apoyo in 1991, by an individual with great plans for fishing and a bucket full of the sleepers just caught in a nearby lake.

In a collaboration between the University of Turku, Finland, the University of Konstanz, Germany, and FUNDECI/GAIA, we compared the responses of two ecologically similar Amphilophus cichlids in the two lakes. The defensive responses to predators of arrow cichlid, Amphilophus zaliosus, in Lake Apoyo were compared to that of Amphilophus sagittae in Lake Xiloa. The arrow cichlid demonstrated evolutionary naivete, allowing this dangerous predator of fry to reach closer to its nest than its counterpart in Lake Xiloa. The results were just published by Topi Lehtonen, Jeffrey McCrary, and Axel Meyer, in January 2012 in PLoS One, a journal of cutting-edge biological science research.

These results are of vast importance, because the arrow cichlid is now officially an endangered species. It is listed by the IUCN as Critically Endangered. Its population is extraordinarily small, its habitat limited to Lake Apoyo, and its threats now include an exotic predator. Our monitoring of this fish, and its fellow Midas cichlid species, is more important than ever. In the context of Lake Apoyo, the bigmouth sleeper is an invasive species with dangerous qualities.

Taken from the Abstract:

" Introduced species represent one of the most serious global threats to biodiversity. In this field-based study, we assessed behavioural responses of brood tending cichlid fish to an invasive predator of their offspring. This was achieved by comparing parental defence responses of the endangered arrow cichlid (Amphilophus zaliosus), a fish species endemic to the crater lake Apoyo in Nicaragua, towards the bigmouth sleeper (Gobiomorus dormitor), a formidable predator of cichlid fry, and all other potential fish predators of offspring. The bigmouth sleeper was recently introduced into Apoyo but naturally co-exists with cichlids in a few other Nicaraguan lakes. Arrow cichlid parents allowed bigmouth sleepers to advance much closer to their fry than other predators before initiating aggressive brood defence behaviours. Interestingly, parents of a very closely related species, A. sagittae, which has coevolved with bigmouth sleepers in crater lake Xiloa´, reacted to approaching bigmouth sleepers at comparable distances as to other predators of cichlid fry. These results provide a novel demonstration of the specific mechanism (i.e. naive parental behaviour) by which invasive predators may negatively affect species that lack the adequate behavioural repertoire."

If you are interested in seeing the arrow cichlid up close and personal, go scuba diving with us. We monitor the fish populations of Laguna de Apoyo and certified open-water divers can join us in a monitoring dive.

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Intensive Course-Biodiversity of Freshwater Fishes

Estacion Biologica in Laguna de Apoyo Nature Reserve gave a course in tropical fish biology and biodiversity in 2010. The students were from US, Germany, Honduras and Nicaragua. The course was directed by Jeffrey McCrary. There were field activities in Lake Apoyo, Lake Masaya, and in two streams in La Conquista on the Pacific Coast.

Jeffrey McCrary explains morphological details for the identification of a fish from Lake Masaya. LA PRENSA.

The course covered the following topics:

1. Freshwater fish diversity in Nicaragua.
2. Taxonomy.
3. Field techniques in population and ecology of freshwater fishes.
4. Midas cichlid phylogenetics.
5. Freshwater fish ecology and conservation issues.

The little Apoyo cichlid, Amphilophus astorquii, in Laguna de Apoyo, Nicaragua. Photo by Ad Konings.

The arrow cichlid, Amphilophus zaliosus, in Laguna de Apoyo, Nicaragua. Photo by Ad Konings.

FUNDECI/GAIA periodically offers courses in wildlife management, tropical biology, and natural area management. If you would like to register for a course, please let us know!

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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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The little Apoyo cichlid, Amphilophus astorquii

The most common cichlid fish in Lake Apoyo is the little Apoyo cichlid, Amphilophus astorquii. It was officially discovered as the culmination of years of study in Estacion Biologica, in a publication in 2008. About three-quarters of the cichlid fishes seen in Lake Apoyo are this species. They breed from December through February, as is shown in the photograph below.

When breeding, thin, light bars appear over a bluish-black background. The dark coloration emerges from dark dorsolateral spots which remain when the fish is not breeding. The males are always noticeably large than the females in any given breeding pair. The breeding pairs form over a hole and utilize a hard surface such as a rock to attach eggs, which are cared as they hatch to form wigglers which later detach to swim freely. The parental units stay actively care for the fry until they are free-swimming approximately forty days. If parental protection is lost, the fry will be eaten by predators within minutes. 

An important component of the diet of the little Apoyo cichlid is snails (Pyrgophorus coronatus). During 2011, two volunteers collected data on the snails of the lake, in an effort to understand better the food webs which must be protected for these fish. These volunteers studied Spanish while working with our staff to collect field data. SCUBA divers collected samples of snails in different habitats and then analyzed them.  

Males often develop nuchal humps as the one in this photo, as a secondary sex characteristic. This fish is in nonbreeding coloration, showing a light, neutral background color, and dark dorsolateral spots. Vestigial dark vertical bars can be seen faintly above and below the spots. When the fish begins its transformation to breeding coloration, these bars will darken and thicken, including the head, leaving the light coloring on the fish limited to thin regions between the bars.

The little Apoyo cichlid is only found in Lake Apoyo, as is confirmed by a recent phylogenetic study conducted by Matthias Geiger, Jeffrey McCrary and Uli Schliewen, in coordination with Estacion Biologica. They are easy to observe, and our monitoring project gives us lots of opportunities to watch them year-round. Other members of the Midas cichlid species complex in Laguna de Apoyo are: Amphilophus chancho, Amphilophus flaveolus, Amphilophus globosus, Amphilophus supercilius, Amphilophus zaliosus. In addition, the jaguar cichlid, Parachromis managuensis is found in the lake; the molly, Poecilia sphenops; and the silversides, Atherinella sardina. Recent introductions of Gobiomorus dormitor and the Nile tilapia, Oreochromis niloticus, can be found as well.

You are welcome to join us in a SCUBA dive to see these fish in their natural environment.

All of the above pictures were taken by Ad Konings, and copyrights are preserved. Ad is a great colleague and friend, and we are grateful that he has taken interest in the cichlid fishes of Nicaragua. Please do not use these photographs without permission.

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