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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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!

Amphilophus astorquii in a multispecies school

Lake Apoyo is populated by several endemic fish species. These fish species have all derived from the Midas cichlid (Amphilophus citrinellus) in Lake Nicaragua. Being a volcanic crater lake, it is isolated completely from other bodies of water. The first discovery of a fish endemic to Lake Apoyo occurred in 1976, while others have been discovered in 2008, and in 2010, and yet more are to be discovered. Estacion Biologica FUNDECI/GAIA conducts a monitoring program which keeps track of the fish populations and other environmental aspects of Lake Apoyo. Here is a photographic summary of the past week's monitoring, thanks to our SCUBA dive buddy Balazs Lerner, as he and our technician dive Laguna de Apoyo.

How many species do you see in this photo? All the fish in this photo are endemic species from the Midas cichlid species complex. It was taken at about 35 feet depth (11 meters), in Lake Apoyo, while SCUBA diving.  And yes, there are several species in this photo. This season's breeding is just beginning in Lake Apoyo, but most of the fish in this frame have not begun breeding behavior. We count fish and nests monthly in the lake.

This is an excellent example of Amphilophus astorquii, the Little Apoyo Cichlid. It was named after Father Ignacio Astorquii, a Spanish biologist and Jesuit priest who dedicated his scientific efforts to the fishes of the Nicaraguan Great Lakes watershed, which includes Lake Apoyo. This fish is in basic (i.e. nonbreeding) coloration.

A mixed-species school of Amphilophus cichlids.

This fish suffers from cataracts, likely induced by parasite infection. We are monitoring the environmental health of the lake as well, as blindness is related the recent introduction of Nile tilapia (Oreochromis niloticus) into Lake Apoyo.

Ascending at the end of another dive. Job well done!

You can help us continue to discover and protect rare species of fish in Nicaragua by participating in our monitoring program as a volunteer or by making a financial contribution. You can accompany us on a monitoring dive (certified SCUBA divers, of course), also. The fish of Lake Apoyo are in danger of extinction, and your contribution to our efforts helps us inform the Nicaraguan government and international scientific community regarding the conservation status of these species. Please give (via PayPal) to our program! Thank you!

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