Scientific Tourism in Estación Biológica Laguna de Apoyo

For the second time in a week, Estación Biológica Laguna de Apoyo has received reportage in the edition 3 July, 2017 of El Nuevo Diario. Our research station is a point of participation for the protection of Laguna de Apoyo Nature Reserve, through activities in scientific research, environmental education, and conservation activities. Click on the link above and take a look!

GAIA scientist Jeffrey McCrary conducts underwater monitoring in Laguna de Apoyo. Photo Garey Knop.

How to make a center for research, conservation, and education work, we have found, is not easy. We often are in debt, but we carry on. There are plenty of gratifying moments and activities for all of us, which is why we continue. We get to help in small ways to cure nature of the ills caused by humans, through rescue of wild animals, planting and caring for trees, recycling, organizing, educating, coordinating with communities and the government, studying the issues facing the continued protection of the area, and developing policy recommendations. One of the many examples of our success is found in the long list of publications in which we have been involved.

A few areas in which we have worked are mentioned in the cited article. We were involved in getting motorboats and jet skis off the lake permanently. This has been a great advance in the protection of the nature inside the lake, and also makes for a much more pleasant and safe experience for all. Boats have meant ugly noises and danger from constant encroachment onto the spaces of swimmers. Everyone, except the few boaters, are glad they are gone. There are plenty of places to take motorboats, such as Lake Nicaragua, so all people win by the elimination of motorboats from Laguna de Apoyo.

The chancho cichlid, Amphilophus chancho, is one of five fish species from Laguna de Apoyo discovered in studies coordinated by GAIA. Photo Adrianus Konings.

Our group has discovered five species of fish that are only found in Laguna de Apoyo. All of these species are descendants of the parent fish of the so-called Midas cichlid (Amphilophus citrinellus). Research coordinated by GAIA demonstrated that the five species in Laguna de Apoyo are genetically distinct from forms in all the other natural areas inhabited by the Midas cichlid.

Scuba divers can join us in monitoring activities on the fish populations in the lake. We are the only approved dive center in Laguna de Apoyo Nature Reserve, and we conduct all our activities in cooperation with the local municipal authorities, MINSA, MARENA, and INTUR.

GAIA maintains the costs of operation of Estación Biológica Laguna de Apoyo through visits, donations, sales of lunch and coffee, hostel stay, and training activities such as intensive Spanish courses. We hope you visit us and get to know what we do. Please come by or write us.

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Jaguar cichlid in Laguna de Apoyo, Nicaragua

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Many cichlid fish species evolved in the Nicaraguan Great Lakes system. Among the more popular of the fish of this region are the guapotes, fish of the genus Parachromis. Guapotes can make a very nice fish dinner. The most abundant of the guapotes in the San Juan River and the Nicaraguan Great Lakes is the Jaguar cichlid, Parachromis managuensis. In Nicaragua, it is known as the guapote barcino, in reference to its checkerboard spotted pattern. Along with several species from the Midas cichlid species complex, the Jaguar cichlid make nests in which parental care observations can be made easily during SCUBA diving.

All the mating cichlids native to Nicaragua protect their young for several weeks after hatching. The guapotes have some important structural advantages to parental care over the more common Midas cichlids found in their range. First of all, the guapotes are large, and therefore can sustain large egg loads. It is not uncommon to see over 2000 fry at Jaguar cichlid nest. Secondly, the guapotes all have large mouths adapted to capture fast-swimming fishes. A bite of the Jaguar cichlid could be fatal even to a medium-sized fish. Potential predators know this and tend to avoid the risk of a bad bite.

These hatchling Jaguar cichlids are less than a week old. They stay near the parental units within reach of a natural or dug cave, and they receive parental care up to about 60 days after hatching. Photo by Martin Cabrera. 

Along with several bird species, the Jaguar cichlid sits atop the food web in Lake Apoyo, Nicaragua. It is the only fish in the lake that can kill and consume up to medium-size fish. Adult Jaguar cichlids only eat fish and perhaps crabs.

Hatchling P. managuensis are prone to move toward the diver, a camera, a hand. Photo by Martin Cabrera.

Male Jaguar cichlids differ morphologically from females in its upturned mouth and other aspects of head shape. Like all the other cichlids native to Nicaragua, the males in breeding pairs always exceed the females in size.

This female Jaguar cichlid is never far from her free-swimming fry. Photo by Martin Cabrera.

All cichlid nests can be fascinating, and the Jaguar cichlids are not unique in this respect. Parents may move little in defense of their fry, but they usually don't have to do much, to get the point across to potential predators.

Most cichlids in Nicaragua utilize natural features such as caves and holes to defend their offspring. This Jaguar cichlid is watching her fry just outside of this crevice. Photo by Martin Cabrera.

Breeding seasonality of the Jaguar cichlid is not as strong as in the Midas cichlids in Lake Apoyo. Whereas the Midas cichlids may reproduce in only two to four months during the year, the Jaguar cichlid is found in reproduction most of the year.

A female Jaguar cichlid (P. managuensis) in her nesting site. Photo by Martin Cabrera.

All cichlid fishes in Nicaragua provide extensive parental care to their fry for the first several weeks after they hatch. There is fierce competition among the Jaguar cichlids for high-quality breeding sites such as this one in our photographs. This site is actually a cave under a large rock, with openings on both ends. The male parent of this nest has little or no continued relation with the nest, however. Big male P. managuensis are scarce, and the males tend to abandon nests earlier than the female, in contrast with many other Nicaraguan cichlids. Big males are easily harpooned when on nest, and unscrupulous SCUBA divers often harvest this fish, as a trophy and for a great meal.

This female is emaciated from the physical stress and reduced food intake associated with reproduction. Photo by Martin Cabrera.

Fry feed on detritus and phytoplankton/zooplankton. They stay close to their fellow fry at all times, depending on the maxim safety in numbers. Among the most dangerous predators of cichlid fry are the Bigmouth Sleepers (Gobiomorus dormitor), introduced into Lake Apoyo only 22 years ago. Both adults and juveniles can catch cichlid fry, especially when a single fish has separated from the group. Fry face a much greater risk of capture when separated from their siblings.

Mother P. managuensis and her fry in Lake Apoyo, Nicaragua. Photo by Martin Cabrera.

We at FUNDECI/GAIA are working to determine the population structure of the fishes, plants and other life in Lake Apoyo, Nicaragua. This delicate lake is under tremendous pressure from people who want to do things that affect the lake: fish unsustainably, cultivate agricultural products using agrochemicals, build houses and install grassy gardens which use copious quantities of water and leave pollution in the lake. With a population baseline, we can determine variations in populations of the different fishes and plants which may result from human-induced alterations in the lake.

This female guapote barcino tends to thousands of fry. Photo by Martin Cabrera.

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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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