Anableps - the Four-eyed Fish (Cuatro-ojos)

Anableps dovii Gill - The Four Eye Fish

Way back in1955, a man name William A Sternke who owned a thriving tropical fish farm in Miami Florida set out on a mission to bring a truly unusual fish to the aquarium. The adventure that followed brought us the Anableps, also called Cuatro- Ojos (Spanish for “four-eyes”) in its native Central America and northern South America. Still available today, though rare, this fish is not only fascinating, it is a live-bearer that has 2-inch young and can see above and beneath water simultaneously.

Anableps are a great novelty of the fish world. Although this olive-colored fish does not really have four eyes, an eye that sees two different images at once is remarkable enough to start many conversations in any circle of friends or academics.

First a little about the fish that still takes people by surprise, usually seen in public aquariums, but still occasionally available for the home enthusiast. Calm, easy to care for, and a real conversation starter, the Anableps seem like a creature from another planet. There is simply nothing like this fish in nature if you have never seen one I highly suggest you seek them out!

Imagine a fish that sees out of the water and in the water, at the same time. Scientists would be hard put to design an eye with such a capability. Yet nature has produced a fish with remarkable simultaneous aerial and aquatic vision. Anableps have perhaps the most complicated eyes in the animal kingdom.

While Anableps has only two eyes, in reality, they function like four.

Anableps habitually swims at the surface of the water with half of its bulging eye above water and half beneath the surface. The upper half (above the water) looks through the air for birds and other enemies. At the same time, the lower half looks through the water in search of food.

To keep its eyes from drying out, Anableps frequently ducks its head under the water for an instant.

A local aquarium store in Orlando Florida that specializes in live plants and aquascaping, Dark Water Aquatics, had a pair of these remarkable fish in an artificial running stream setting. It is hard to describe how amazing it is to see them live and in action.

The eyes of the four-eyed fish are a marvel of optical engineering. The iris of the eye is divided in two- precisely at the water line. Aquatic vision requires a thicker lens than aerial vision. Anableps has an egg-shaped lens, with the pointed end downward. Thus, light from the water passes through the long dimension of the lens, and light from the air passes across the short dimension.

By this means, the same lens serves the purpose of forming two different images at the same time. Further, this fish’s eye has two separate retinas, one on top and one on the bottom. Things the fish’s eye sees from above the water focus on the lower retina, and things are seen in the water focus on the upper retina.

The Anableps averages 6 inches in length full grown and is relatively rare to find for sale in pet stores, but its limited ability is due, in great part to the efforts of William A.

Sternke. Sternke, a professional breeder and commercial fish farm owner in Miami, Florida, in the 1950s through the 1970s, collected these strange fish and was believed to be the first to breed the Anableps in captivity.

In fact, he's believed to be responsible for the distribution of this amazing fish to the United States, then all North America and later around the world from his modest commercial fish farm in Florida. Ann article in The Aquarium in May 1957 gave an interesting account of how Mr. Sternke collected Anableps in Mexico:

“The fact that others had failed did not deter Sternke when Carlos Boner approached him with the idea of going to Mexico to get some four-eyes. Boner had been born in Mexico and knew the country well; in fact had brought back some four-eyes before, but had been unable to keep them alive. Deciding he would like to try where others had failed, Sternke journeyed to the West Coast of Mexico in March 1955, and Boner showed him where he had gotten his other Anableps. Sure enough, there were Anableps, in a stream a stone’s throw from the ocean which contained brackish water – and sewage. Sternke shook his head. Then he looked inland. He saw a swath of green cutting a winding pathway through the arid land. ‘Let’s go up there and get some Anableps’, Sternke said, pointing towards the mountains. There, in the fresh, clean waters of an ageless river that ran shallow through gorges and around mountains they found the incredible fish with the double eyes in each socket. Choosing a precipitous spot where the water was slow-moving, they had natives dam the river and they went to work with a seine net. But this did not prove efficacious, as the fish simply leaped over the net. Finally they had to settle for the hand net. Sternke took care to select younger fish which were not full-grown, reasoning that they would be more adaptable to change. Thirty of these young fish he shipped back by air to his Sunnyland Fish Farm in Miami, Florida, where Mrs. Sternke had the N0 1 outdoor pool ready for them. Despite expert care, 13 died within the first two weeks, but the remaining 17 survived and today present evidence of a triumph in fish-keeping for any Anableps you see are from this expedition by William A Sternke.”

Compatibility In Community Aquarium

Anableps is ordinarily a rather lazy fish, but it can move rapidly when it wishes to do so. When frightened it skitters across the surface of the water and occasionally leaps right out of the water. If it sees a smaller fish or some other morsel of food, it dives and catches its victims with some skill. Yes, as you may have ascertained by this, they are not good community tank mates, unless they are with larger fish, but since they are soft body fish, the larger fish must be non aggressive themselves.

Breeding the Anableps

As Mr. Sternke observed all those years ago, the breeding habits of the Anableps in the wild and how they are bred in captivity is no more difficult than the breeding habits of a molly, though somewhat more dramatic due to their size. They are classic live-bearers.

Baby four-eyed fish are born alive and up to 2 inches in length. By means of a special anal fin (called a gonopodium), the male deposits his fertilizing sperms inside the female. The eggs remain inside the female until they hatch, and we know today, there is more to it than this. There is a symbotic relationship between the mother and the fry while inside her. A female Anableps has only two to five babies.

For the size of the parents, the newborn are quite large, two inches on average. The abdomens of the babies are completely open for the first few days, making them extremely venerable to predators, as if the internal organs were all exposed. Then the abdominal opening gradually closes, without leaving a scar. The adults offer no assistance to the young, however they are not cannibalistic, they simply ignore them. In nature they give birth in the weeds or cover and swim away.

The Cost and Care of Anableps 

Anableps is expensive, rare and difficult at best to keep. It requires a very large and specialized aquarium set up to make them happy and for them to have any chance to survive. Only a real expert breeder looking for an extreme challenge should even attempt breeding this fish, but seek out this unusual fish, look and marvel at its splendor.

The Anableps truly is one of the wonders of nature and of the Aquarium world still today, a true oddity.