Month: June 2021

Four Eyed Fish

Sure, those of us who wore glasses when we were younger may have been called “Hey, four eyes!”.  But I bet none were ever taken to the level of “Hey, four eyed fish!”.  ‘Cause that would be combining two insults, the discrimination against an ocular disability and the idea that you were kind of cold…or wishy-washy…well, anyway.  I sometimes get to share the fact that I once caught a four-eyed fish, and would like to share some very interesting information about the species.

(Imagine me affecting a British accent here, to make my story sound more adventurous).  “There I was, standing in the river with my doughty crew, when one of the young stalwarts excitedly shouted “Quatros ojos, quatros ojos!””.  Yes, just a few feet away from me cruised the rare and dangerous (dangerous if you’re an insect, that is) Pacific four-eyed fish!  Alright, enough of that…

In 1999 I accompanied members of my church on a mission trip to the area of Siguatepeque, Honduras, to assist in building cement block housing for victims of Hurricane Mitch (in 1998 Mitch was responsible for the death of at least 11,000 people in Central America) that caused a flood perhaps 40 feet deep in a valley near Siguatepeque.  After the rest of the group left I stayed behind to travel to the Pan American School of Agriculture near Tegucigalpa,

where the fisheries instructor there graciously allowed me to accompany them on trips to waters near the school.  The streams we sampled were the mainstem and tributaries of the Rio Choluteca, the major river on the Pacific slope of Honduras that winds through mountainous terrain until it empties into the Gulf of Fonseca (an estuary shared by El Salvador, Honduras and Nicaragua).  At a site on the Choluteca, near the village of Zamorano, the school’s students and I seined up the Pacific Four-eyed Fish (Anableps dowi).  This was a species I’d read about prior to making the trip, so when I heard the student’s cry I became quite excited!

 

The species was named for a Captain J. M. Dow, who skippered the steamer “Guatemala” of the Panama Railway Company.  Captain Dow collaborated with two associates to send over specimens from over 1500 samples in Central America to the U.S. National and the British Museums.  The reason for the Foureyes’ common name is actually due to the presence of two pupils in each eye, one in the upper and one in the lower half and separated by a band of tissue; enabling them to see above and below the water while they cruise at the surface of the water body.  That ability makes the foureyed fish extremely difficult to catch with a seine since they are able to see you (or an eagle, or other bird of prey) coming from a long ways away.  They are known to leap right over a seine and like other “topminnows” they dive down to the bottom to avoid capture.  An effective method of capture is described as using a group of fishermen to drive a school of cuatros ojos toward a concealed individual waiting with a cast net that is thrown over the school, ensnaring a “bushel full” of the prey.

 

 

The eye is flattened on the top and rounded on the bottom half, with a thickening of the lens from the bottom to the top to adjust for the refractive differences in the two mediums.  This structure has inspired at least one contact lense company to develop lenses that work extremely well both out of and in the water.

 

The Four-eyed fish eye. 1.Underwater retina 2.Lens 3. Air pupil 4. Tissue band 5. Iris 6. Underwater pupil 7. Air retina 8. Optic nerve

Swimming at the surface with the head exposed is relatively unusual for fishes in general, but species of the genus exhibit other oddities as well.  Not only do the quatros ojos leap out of and skip along the surface of the water, but when they see terrestrial insects on the banks they will actually leap onto the shallow, inundated bankside areas to capture their prey.

 

Once they’re out of the water their mobility is severely limited since unlike eels they cannot locomote with a wriggling motion, nor can they push off with their tails to leap forward on land, and unlike mudskippers and the “walking” catfish their pectoral fins are unsuited to pulling themselves along.  So although they may push themselves along with their tail and pectoral fins to chase their prey the extent to which they are able to do so is severely limited.

 

Another anomaly that characterizes anablepids is that their genital organs are oriented either to the left or right, thus they can reproduce only with mates having compatible organs.  They share this character with the group of species to which they are said to be most closely related, the “One-Sided Livebearers”, or Jennysina.  The functional significance of this anomaly is not known…  The male of the species has a gonopodium; a modified anal fin ray that develops as the males mature and facilitates placement of the sperm into the oviduct, fertilizing the female’s eggs.  The eggs are carried to term inside follicles in the female’s ovary but nourishment is provided by a yolk sac within the egg.

Anableps congregate in schools of up to 200 or so as juveniles, with their gregariousness decreasing with age until at adulthood they are as likely to be found as individuals as in small groups.  Some of their known fish associates include characins, pimelodid catfish, poeciliids, atherinids, eleotrids, flatfishes and cichlids.

 

The Family Anablepidae is placed within the Order Cyprinodontiformes (the Pacific Foureyed Fish is the largest species in that order).  That order contains a bounty of fascinating forms, with a wide variety of reproductive types, a plethora of adaptations to environments, and high importance in terms of biogeography.  Cyprinodontiformes is made up of families that for the most part exclusively are either oviparous (egg laying), ovoviviparous (live-birthed from eggs) or viviparous (live-birthed from embryonic development without eggs).  Species of the family Anablepidae are found in rivers and streams (some (such as the Pacific Four-eyed Fish) live and thrive in euryhaline and even marine areas) from Mexico to South America, and are ovoviviparous, or live bearers; similar to guppies and mosquitofish.   Owing to the ability of many species to tolerate a wide range of salinities the cyprinodontoids are able to move along the coast from one stream to a neighboring stream.  It is thought that this plasticity has enabled certain groups to disperse throughout southern Mexico to northern South America.

Anableps have an unusual and interesting lifestyle. They spend almost all of their time at the surface and rarely swim underwater. They will dive down when they spot a food item, though, using their large, paddle-like pectoral fins for a burst of speed. They will also leap onto mud and sand banks during periods of low-tide to snatch terrestrial insects. These fish have been observed lying in the sun, sometimes for several minutes, before pushing their way back into the water.

Four-Eyed Fish are moderately hardy, but they are comparatively large livebearers, growing to around a foot in length.  Since they are surface swimmers they do best in a long, relatively shallow tank in (depending on the species) fresh to moderately brackish water.  They are gregarious so don’t keep them singly or in pairs.  They will probably do well with Sailfin Mollies, bottom-dwelling Gobies, Mudskippers, and even Orange Chromide Cichlids, Archer Fish and Monodactylus.

Once Upon a Time a Beautiful Fish Lived There

In the colder waters of North America lives what is perhaps the most beautiful freshwater fish, the Arctic Grayling.

What an elegant animal!  Sometimes called the “sailfish of the north”, this species is best known for the large dorsal fin that exhibits gorgeous colors!

The arctic grayling is circumpolar in distribution, with stable populations across northern North America from Alaska to Newfoundland Canada, and across northern Asia from westernmost to easternmost Russia.   So, while there is no danger of extinction across the worldwide range of the species, one population in Michigan was extirpated, and the only other known, native population in the contiguous United States, in Montana, was almost extirpated as well.

Once abundant enough to “walk across the river on the backs of the fish”, native populations of the Michigan grayling are extinct.  Their demise resulted from logging that removed the large trees along the banks of the rivers and streams that served to cool the waters along with the practice of sending the cut logs downriver that destroyed habitat and impacted the eggs and larvae in the rivers, and unrestricted fishing during the spawning season.

Arctic grayling were successfully stocked  a few years ago in privately owned Brookhaven Lake Brookhaven Lake (brookhaven-lake.com) near the south-central portion of the Upper Penninsula Michigan, and can be fly fished there with reservations.  But there are currently collaborative efforts underway to stock nearly identical subspecies of the arctic grayling in the Manistee River that flows into Lake Michigan.

We have two specimens from Michigan, one a skin mount from a grayling caught in 1880 from the Au Sable River in Michigan, the other caught in 1938 by longtime OSU-MBD curator Milton B. Trautman (huh…”Trautman”…figures eh?) from Ford Lake in Michigan, where the species was stocked.  The Au Sable River heads up near Grayling, Michigan (of course!) and flows into Lake Huron through (what could be more appropriately named than) Au Sable, Michigan.  A total of 15 arctic grayling vouchers are cataloged at the OSUM (Ohio State University Museum of Biological Diversity) from Alaska, Michigan, Montana, Ohio, and Ontario Canada.  One of those vouchers represents one specimen caught in 1968 from Lake Erie near Cleveland Ohio, but this specimen either was stocked by the ODNR or from a private lake, or strayed from Ontario (where it was stocked and is listed as an exotic species), or southern Michigan.

References: California Academy of Sciences Catalog of Fishes, Hubbs and Lagler Fishes of the Great Lakes, Scott and Crossman Fishes of Canada

Arctic Grayling (Thymallus arcticus) – Species Profile (usgs.gov)

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4874605/pdf/pone.0156187.pdf

A Marvelously Successful Invader

Consider the round goby, a much maligned fish species due mainly to their success in colonizing many waterways including the Great Lakes.  One might wonder whether more fishermen have cursed the ugly, unappetizing fish when it greedily grabs their bait than have berated the other “useless” invader; common carp, in the few years the goby has been in the Great Lakes compared to common carp that were introduced intentionally across the country by the U.S. Fish Commission in the 1880’s.  In all actuality though, there is much to be admired about this quarter-pint-sized interloper!

The first round goby taken in Lake Erie was electroshocked by Dr. Roger Thoma, formerly of the Ohio EPA Surface Water Division, inside the breakwall at the Grand River harbor in 1993. Given the distance of the first sighting of the round goby from the St. Clair River where it first appeared in 1990, the goby may have been in Lake Erie a couple years before 1993.

If you were planning to invade an ecosystem, what skills would you have that would enable you to do so as efficiently as this happy little fish in the picture below?  One characteristic would be a sound reproductive strategy, and the round goby excels in this area with eggs that are larger than other species of similar size enabling better survival of the young, especially when coupled with the strong parental care exhibited by the round goby.  The male tends the nest, cleaning and guarding it from predators.  Round gobies are known to be highly aggressive, invading the most suitable territories for their nests and predations, as well as waiting rapaciously for much larger black basses to leave their nests even for a moment to grab a morsel to eat at which point the pugnacious goby rushes in to gobble up eggs and larvae.

 

So, is the only good round goby a dead round goby?  Not in the strictest sense, if you’re a Great Lakes water snake, or a cormorant (that also prey on and have benefitted from the “explosion” of the water snake population), or even a bass.  See, those are all just a few of the many animals that have benefitted from the abundance of round gobies.

 

The Olentangy River Shark

Source: https://mexican-fish.com/atlantic-sharpnose-shark/

How in the world did this shark swim up into the Olentangy River?!  Do we need to worry about our dogs retrieving frisbees thrown from the banks of the river?

No, no worries.  This species is exclusively marine and would never enter freshwater streams although they may stray into estuaries from time to time, their bodies could not adapt to the change in salinity unlike the bull shark and several other fish species.

But on 08 August 1976 an Atlantic sharpnose shark was found on the bank of a tributary to the Olentangy River…dead.  How did it get there?  Perhaps someone caught it off the shores of New Jersey where they are one of the most common shark species Atlantic sharpnose shark – Wikipedia in the nearshore waters of the west central Atlantic Ocean.  Even if they could survive in freshwater they seldom attain more than 4 feet in length.

Oddly though, just a little less than 40 years later another Atlantic sharpnose shark was found floating, dead, in the Ohio River near Manchester Ohio and is also vouchered here in the OSUM Fish Collection (mbd.osu.edu/collections/fish-division).

For more information on these specimens OSUM 54284 and OSUM 115521 navigate to mbd.osu.edu/collections/fish-division, click on the Fish Division Database bar and enter OSUM and the number into the search bar.  Alternatively you can search for this and other species in our database for vouchers held in our collection.