More than just a pretty (fish) face – Do you recognize some of these small fish from your aquarium?

As I mentioned in Monday’s post, species in the genus Anableps post the largest size (at just about a foot long) in an order of rather small fishes, the Cyprinodontiformes. Don’t let their small size fool you, it does not reflect their importance in several areas. Many are quite easy to raise, and some are cultivated for beautiful colors, particularly in their fins. Unfortunately, being popular fishes in aquaria frequently results in introductions to non-native areas from aquarium owners. In several instances exotic populations have become established. Here are some of the more enigmatic species that the OSUM Fish Division has vouchers for, arranged by family:

CYPRINODONTIDAE

Sheepshead Minnow, Cyprinodon variegatus, occur along the Atlantic coast from Massachusetts south to northern South America.  Abundant and easily cultured for the aquarium trade, also used as bait.  One introduced specimen was actually caught (back in the 1950’s) next to the Olentangy Indian Caverns in a small stream tributary to the Olentangy River.

Flagfish, Jordanella floridae, are common in the St. John’s and Ocklocknee Rivers to southern Florida. This species is listed in The Guinness Book of World Records as the fish with the fewest eggs, laying only 20 over several days.

FUNDULIDAE

Members of this family are distributed across North and Central America including some of the Caribbean islands, in coastal and interior low gradient, slow moving rivers, streams, and swamps.

Male Northern Studfish; note the twisted maxilla (posterior portion of the upper jaw bone) that is characteristic of the Fundulidae, photo by Uland Thomas

Northern StudfishFundulus catenatus. Although reputed to be difficult to keep it is popular in the aquarium trade because of the male’s vibrant breeding coloration. This species is native in disjunct populations in several states along the Ohio and Mississippi Rivers, but has recently been introduced and established in small to medium streams in Ohio and West Virginia.

OSUM 104822 Fundulus catenatus

OSUM 104822 is the voucher for the first specimen found on the eastern side of Ohio, in little Pipe Creek, across the Ohio River from Graves Creek in West Virginia, where there is a well established and thriving population that is believed to have been intentionally introduced.

Golden Topminnow, Fundulus chrysotus.  Common in Florida, but can be found in low lying swamps and backwaters from North Carolina along the Atlantic seaboard and around the Gulf of Mexico to eastern Texas.

 

Female Mummichog, photo by Dave Neely

The MummichogFundulus heteroclitus, frequently spawns inside mussel shells, a life history attribute that is hypothesized to be facilitated by a very long urogenital sheath.

The Diamond Killifish, Fundulus xenicus, inhabits marine, freshwater and brackish waters of the Gulf of Mexico shoreline from Florida to Mexico.

Bluefin Killifish, photo by Julie Zimmerman

Bluefin Killifish, Lucania goodei

Male Rainwater Killifish, photo by Brian Zimmerman

Rainwater Killifish, Lucania parva

GOODEIDAE

This family contains many species that are critically endangered in Mexico and Central America, due to their endemism to restricted bodies of water that are denigrated by anthropological modifications.

Tuxpan SplitfinAlldontichthys tamazulae, is endemic to the Rio Tuxpan in the State of Jalisco, Mexico.

Butterfly SplitfinAmeca splendens, is endemic to the State of Jalisco, Mexico, raised and sold commercially to the aquarium trade.

Redtail Splitfin, Xenotoca eiseni, are listed as endangered and declining.  The species was split as recently as 2016 to add two new species from the original distributions, where the critically endangered X. lyonsi is found in the Tuxpan and Tamazula Rivers and the critically endangered X. doadrioi in the “endorheic region of Metzatlan in the state of Jalisco, Mexico”.

POECILIIDAE

Possibly due to the ease of breeding, this family contains many popular aquarium species like guppies and swordtails.  One species, Poeciliopsis latidens, lives in marine waters, although several others are secondary freshwater species.

Sailfin MollyPoecilia latipinna, is native to coastal lowlands from North Carolina to Vera Cruz, Mexico, but has been introduced to many countries with “adverse ecological impacts” reported.

Variable Platy, Xiphophorus varietus, is endemic to Mexico but is another popular aquarium fish that has been carelessly introduced with resultant harmful ecological impacts (for this species the impacts are primarily competition with native fishes for resources).  These and several other species in the genus Xiphophorus are listed as exotic pests by governmental agencies.

The fact that many cyprinodontiforms (and cichlids) are tolerant to higher salinities as opposed to the primarily freshwater orders of fishes has made them the subject of biogeographical studies particularly for dispersal from one stream to another along coastal areas.  It is hypothesized that their adaptability to variable habitat conditions facilitated their invasion and predominance of the Central American fish fauna as they made their way across the narrow, open waters from South America to Central America before the rise of the Panamanian isthmus.  This hypothesis, formulated by ichthyologist George S. Meyers in the mid ’60s, has been strengthened by genetic work in the current decade.

Photo Credits:
All photos of museum specimens were taken by Marc Kibbey; other photos with permission of members of the North American Native Fishes Association (NANFA.org).

Detailed information for each specimen is available through the OSU Fish Division Database.

About the Author: Marc Kibbey is Associate Curator of the Fish Division at the Museum of Biological Diversity.

 

*** Which of these fish species do you have in your aquarium at home? ***

Hey, Four-Eyed Fish!

Sure, those of us who wore glasses when we were younger may have been called “Hey, four eyes!”.  But I wonder if anyone ever took offense to the level of “Hey, you 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 recently I found out that the species belonging to the Genus Anableps that I caught is rather rare, so I feel even more special!

(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 Foureyed Fish Anableps dowei!

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 mission 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.

view of Universidad Zamorano

Universidad Zamorano. Photo by EAP Zamorano [CC BY-SA 4.0], via Wikimedia Commons

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 Foureyed Fish (Anableps dowei).  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!

Drawing of a Foureyed Fish

Drawing by Unknown [Public domain], via Wikimedia Commons

The species is 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 Four-eyed Fish’s common name is the presence of two pupils in each eye, one in the upper and one in the lower half, separated by a band of tissue. This enables them to see above and below the water while they cruise at the surface of the water body and makes the Four-eyed Fish extremely difficult to catch with a seine: 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 fish in another family, 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 quatros ojos toward a concealed individual waiting with a cast net that is thrown over the school, ensnaring a “bushel full” of the prey.

photo of Largescale Foureyes (from above water)

Largescale Foureyes, Trinidad. Photo by Charlesjsharp [CC BY-SA 4.0], via Wikimedia Commons

The Anableps‘ 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.  The upper pupil casts the terrestrial image through the lens on the lower retina, while the lower pupil’s image is reflected on the upper retina.  The Four-eyed Fish’s eye recently inspired at least one contact lense company to develop lenses that work extremely well both out of and in the water.

 

Scheme of the eyes of a four-eyed fish showing the basic functions

Diagram of the eye of a four-eyed fish, [public domain] via Wikimedia Commons

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 this genus show 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 bank side areas to capture their prey.  These fish have been observed lying in the sun, sometimes for several minutes, before pushing their way back into the water.  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. 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.  Anableps species are viviparious, meaning the young are birthed live rather than from an egg deposited in the water.  The eggs are carried to term inside follicles in the female’s ovary at which point they hatch and are extruded from the genital pore.  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.

At present three species of Four-eyed Fish are recognized: Anableps anableps, the Largescale Foureyes, is found in South America from the island of Trinidad and Tobago, and Venezuela to the Amazon Basin of Brazil.  Anableps dowei, the Pacific Foureyes, has the most limited distribution of the three species, occurring in Central America from southern Mexico to Nicaragua. Anableps microlepis, the Foureyes, is the most salt tolerant species of the three. They are found in open marine areas in full seawater (also from Trinidad to the Amazon Basin in Brazil) and follow tidal rhythms, moving up into sheltered lagoons and further upstream with the high tides, and back out into open waters as the tide wanes.

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.

If you are looking for an unusual fish for your aquarium the species that is most commonly available from suppliers (there are several that raise their own stock), the Four-Eyed Fish, is moderately hardy, but they are comparatively large in size, growing to around a foot in length.  Since they are surface swimmers they do best in a long, relatively shallow tank in fresh to moderately brackish water (depending on the species).  They are gregarious so it is best not to 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.

The Family Anablepidae is placed within the Order Cyprinodontiformes (and, the Pacific Foureyed Fish attains the largest size of any 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.  My next post will portray some of those very diverse species.

About the Author: Marc Kibbey is Associate Curator of the Fish Division at the Museum of Biological Diversity.

*** Have you ever seen a four-eyed fish? Let us know, leave a comment ***

A newcomer to the OSUM Fish Division

We have several voucher specimens belonging to the order Salmoniformes, ray-finned fish like salmon, trout, chars, in our holdings, including the Lake Whitefish Coregonus clupeaformis. While common across most of their range, some are considered of special concern or vulnerable in the State of Ohio, for example, the Lake Trout Salvelinus namaycush. Another Coregonus species, the Cisco, is critically imperiled in Ohio, and Bloaters Coregonus hoyi (the hero of Monday’s post) were never found in Lake Erie due to the lake’s shallowness. Bloaters were extirpated from deeper Lake Ontario where the U.S. Fish & Wildlife Service is now reintroducing them. The specimens from the Tom Simon collection are the first Bloater vouchers (e.g. OSUM 117265) that we have for the OSUM fish collection.

By the way, a voucher specimen is a preserved specimen of an identified taxon permanently stored in our collection and retained as a reference. It has a unique identifier (e.g. OSUM 117265) and can be retrieved and used in scientific studies.

When moving the specimens, we needed many helping hands. Here Kai Raab, husband of OSUM Director Meg Daly, assisted with accession of some of the Tom Simon collection.

All Bloater specimens from the Tom Simon collection were trawled by the United States Geological Survey (USGS) during their surveys and have inflated gas bladders due to being brought from depths quickly.

The Bloater’s specific epithet, C. hoyi, is derived from the name of the man who originally discovered it while dredging in Lake Michigan, Dr. P. R Hoy. Dr. Hoy engaged ichthyologist Dr. James P. Milner to describe the species.

Coregonus is a diverse genus of fish with at least 68 described species. Some are easier to tell apart by morphology than others. Lake Whitefish, Coregonus clupeaformis, are separable from the Cisco and Bloater in the field by observing the mouth position: subterminal versus terminal, respectively. Note the terminal mouth, pointing forward, in the Cisco on the right.

Other species are quite similar in appearance and hard to separate in the field. For example, the Cisco and the Nipigon Cisco C. nipigon, as well as the Bloater and the Kiyi C. kiyi look very similar and occur sympatrically in some water bodies. For these and other species in the genus one must count the gill rakers to separate them. Gill rakers are the bony comb-like structure that serve to sieve food as the fish expels water through its gills while it is eating. The gill rakers are shown under the gill cover in the images below, to the left of the gill filaments that function to transfer oxygen from the water to capillaries. Once the food particles are caught on the rakers the fish can swallow them.

Cisco were found to have gill raker counts from 36 to 50, with a mean of 43 in Lake Saganaga and adjacent Minnesota border lakes. While gill raker counts for the Nipigon Cisco range between 45 to 70 with a higher mean than for the Cisco at 56.

Here are some additional species in the genus Coregonus; some are easy to tell apart by their location of occurrence.

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Reference:

Etnier, David A., and Christopher E. Skelton (2003). Analysis of Three Cisco Forms (Coregonus, Samonidae) from Lake Saganaga and Adjacent Lakes near the Minnesota/Ontario Border. Copeia, Vol. 4, 739-749.

 

About the Author: Marc Kibbey is Associate Curator of the Fish Division at the Museum of Biological Diversity.

 

 *** We would like to hear from you – please leave a comment ***

The Bloater: A Complicated Story

You may recall from my last post that I mentioned a fish species from the recent Tom Simon Fish Collection acquisition, the “Bloater” Coregonus hoyi.  This is a species that in the recent past has been considered endangered, indeed it was known to be extirpated from some of the Great Lakes and thought to perhaps be on its way to extinction across the rest of its distribution.  Herein I’ll detail some of the reasons for which the bloater came to be in such peril.  But for now, allow me to follow a rabbitfish trail (ahem):

Perhaps you have wondered why this fish is named so cruelly?  Perhaps, one might think, the name was given in less politically correct days when short shrift was given to a fish’s feelings, but that is simply not the case.  No, the name actually describes the propensity of the species’ swim bladder to expand and make it look fat when it is trawled from the deep, colder waters that it prefers.  So you see it actually does have to do with the poor fish having a tendency to be gassy.

OSUM 117265 Coregonus hoyi "bloater"

Yes, that bladder does make you look fat! OSUM 117265 Coregonus hoyi 195mm SL 1 of 18 specimens from jar 1 of 3

The rapid ascent from the fairly extreme depths, down to almost 700 feet where the fish resides, and consequent distension of the bladder does cause more than just discomfort for the fish. The complexity of the connection to the gas bladder in the bloaters renders them unable to quickly discharge the air and liable to bursting upon fast ascent from depths.  In many species of fish the swim bladder is directly connected to the gut and the fish can use this connection to directly control the amount of gas in the bladder. This physostomous swim bladder occurs mainly in fish living in shallow waters and swallow air that is passed into the gut and forced into the swim bladder. Not so in the Bloater. Fish in the order Salmoniformes, such as the Bloater, share a character with other advanced fishes: the physoclistous swim bladder. This gas bladder has no direct connection to the alimentary canal but some areas of the membrane separating gut and bladder are very thin and well supplied with capillaries that allow rapid gas exchange. This gas gland secretes oxygen into the swim bladder through the rete mirabile, literally “a wonderful net” of capillaries.

Diagram of the arterial/venous transfer to the gas bladder via the rete mirabile

The Bloater is one of several  “whitefish” species that have become rare and imperiled, some to the point of extinction. Bloaters are invertivores – you guessed right, feed on invertebrates – at all stages of their lives and formerly fed in open water (Many other fish species are invertivores at immature stages and shift their diets to larger prey including vertebrates as adults).  It has been documented that bloaters (and some other fish species) have changed their feeding habits in response to competition from the invasive Alewife Alosa pseudoharengus to feed on benthic invertebrates.  Happily for the bloaters they seem to have benefited, in the long run, from the Alewife invasion.

But there are several other reasons for the drastic declines seen among the bloater populations during the mid-1900’s:  Whitefish provide table fare for many piscivorous people, the fish-eaters among you.  The major upswing of humans in the Midwest region caused concordant increases in demand for food sources, and people began to realize that the Great Lakes could provide fish aplenty to help meet that need.  The lakes and rivers of the Midwest states at one time “teemed with fish”, according to several historians that wrote during that era of expansion and discovery. It seemed that the bounty was inexhaustible, and fishermen quickly capitalized on the surging market, filling their trawl nets to capacity for several decades.

Until, at varying points depending on the species being taken, the catches began to dwindle.  Before long the fishermen began to realize that conservationists were correct in their assessment that the boom wasn’t going to last, and regulations were put in place to husband the resources. However, other influences began to make themselves known, some with alarming results. Compounding the effects of overfishing was the connection of Lake Ontario to Lake Erie via the Welland Canal ca. 1830 that enabled incursion of several invasive fish species:  First to make an impact was the Alewife, a relatively small fish species in the herring family Clupeidae. Alewives compete with coregonids and other fish species for planktonic prey, to the point where diets for some forms shifted from zooplankton to benthic foods, feeding at the lowest level of the water body. Those species that couldn’t adapt their diets disappeared, became smaller or declined in numbers.  The next invader to have a significant impact on bloaters was the Sea Lamprey Petromyzon marinus. Sea Lampreys are piscivorous parasites (or is that parasitic piscivores?) for approximately a year of their several years’ long life cycle.  The invasive lamprey arrived in the Great Lakes in the early 1900’s and by the mid 1900’s had decimated populations of several salmoniform species. It is thought that one reason fish species like Lake Trout, and Lake Whitefish and other coregonids, fared so poorly with the Sea Lampreys is that they tend to inhabit deeper, colder areas of the Great Lakes where the lampreys prefer to feed.  For example, bloaters are most commonly found at a depth of 90 – 680 feet in water temperatures between 34-55 degrees Fahrenheit. Thanks to the monumental efforts of our conservation agencies the Sea Lamprey populations are under reasonably good control to the point where Great Lakes fishes are much safer!

 

Reference:

McDonald, M. E., Crowder, L. B., & Brandt, S. B. (1990). Changes in Mysis and Pontoporeia populations in southeastern Lake Michigan: a response to shifts in the fish community. Limnology and Oceanography, 35(1), 220-227.

 

About the Author: Marc Kibbey is Associate Curator of the Fish Division at the Museum of Biological Diversity.

 

 *** We would like to hear from you – please leave a comment ***

Hoosier Fish

Shown below are photos portraying our work to bring the Tom Simon Collection to Columbus.  We are so thankful to Beth Simon, Tom’s wife of 37 years, for honoring Tom’s wishes to gift the collection to the museum.  Beth was a great source of encouragement (including lots of pizza, subs, cookies and drinks and a great attitude) and brought her daugher Lia and son Zachary to assist in the move.  Tom Simon’s family exhibits the qualities that Tom himself exemplified, a true testimony to his character.  May the arrows from Tom’s quiver always fly true.

The old church that Ichthyologist Tom Simon refurbished and transformed to his laboratory

The old church near Bloomington, Indiana that Ichthyologist Tom Simon refurbished and updated to function as his laboratory and fish repository

 

OLYMPUS DIGITAL CAMERA

Marc Kibbey surveys all that he is now “master” of.  The truck was loaded so heavily on the third trip that Marc and Logan had to dig 1 foot under the lift gate to be able to fold it up.  On one of the steep hills along Indiana Route 46 the truck could only muster 25mph on the nighttime drive back, no doubt making the long line of drivers behind a bit testy.

 

Load up! Indiana DNR NonGame Fish Biologist Brant Fisher, Indiana University and Tom Simon student Logan Shank fill up the truck

Load up! Indiana DNR NonGame Fish Biologist Brant Fisher, Indiana University and Tom Simon student Logan Shank fill up the truck.

 

Truck full-o'-fish

Truck full-o’-fish

 

Bloaters, one of several fish species new to our collection (and one of many reasons i'm excited about this gift)!

Bloaters, one of several rare fish species new to our collection (and one of many reasons i’m excited about this gift)!

 

These three carts hold what is numerically the biggest portion of the acquisition, approximately 7 million fish larvae

These three carts hold what is numerically the biggest portion of the acquisition, approximately 7 million fish larvae!  These vouchers were used to help develop a six volume series, “Reproductive Biology and Early Life History of Fishes in the Ohio River Drainage“, co-written by Tom Simon.

 

Logan Shank (aka The Modest Viking), Tom Simon's student ( right of Brant Fisher) is a gentle giant who worked tirelessly on our small crew on the Indiana side.

Logan Shank (aka The Modest Viking), Tom Simon’s student ( right of Brant Fisher) is a gentle giant who worked tirelessly on our small crew on the Indiana side.

Fish Slingers on the Dock

Fish Slingers on the Dock.  Thanks you guys, and to all the rest that helped us in Indiana and at the Museum of Biological Diversity!

Finding No-No

In our Muskingum River Survey we’re searching for a couple (invasive) fish species that we hope we do not find: The Silver and Bighead Carp.  Environmental DNA has been detected in the Muskingum River for Bighead Carp and also for Northern Snakehead, another invasive species from Asia.

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And just as importantly, we’re taking names, numbers, weights and lengths of everything else we catch, documenting Muskingum River’s fish fauna before the Asian carp invade.  Just a few of the native species we’re catching or may catch soon that are found in the Muskingum:

 

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About the Author: Marc Kibbey is Associate Curator of the Fish Division at the Museum of Biological Diversity.

Pre-Asian Carp Invasion: Muskingum River Survey

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Photo of the Muskingum River from the National Weather Service

A little over two years ago a test of the Muskingum River using eDNA techniques showed positive results for Bighead Carp, one of several Asian carp species, and Northern Snakehead.  Although the Ohio Division of Natural Resources (ODNR) and U.S. Fish and Wildlife Service sampled the Muskingum River extensively neither of these invasive species was actually caught.  It may be that the highly sensitive eDNA technique picked up genetic material from bird feet or boat bottoms that traveled from areas where the invasive species were well established, but that has yet to be proven conclusively.

The OSUM Fish Division is currently carrying out a project to survey the Muskingum River watershed from top to bottom under the supervision of project leader Brian Zimmerman, with a grant from the Ohio DNR Division of Fish and Wildlife, overseen by Associate Professor and MBD director Meg Daly. Fifty-five sites above, below and in each of the nine pools between the locks and dams of the mainstem, and 5 each along the two major tributaries of the Muskingum River, Muskingum River lock and dam Photo from the Ohio Canal Society, the Walhonding and the Tuscarawas Rivers, will be sampled.

Muskingum River lock and dam, Photo from the Ohio Canal Society

Muskingum River lock and dam, Photo from the Ohio Canal Society

The sampling techniques will include

  1. Electroshocking: as the name implies, this technique involves the application of electrical current to stun fish, causing them to remain immobile for crew members with pole nets to retrieve them and place them in a large tub in the boat.
  2. Seining: The use of 6’ tall x 8’ wide seine nets by two or three people in this project to sample shallow areas.
  3. Benthic Trawling: We take an 18’ flat bottomed John boat with two 25 horsepower outboard motors and drag a small “otter” trawl net along the bottom of the river.
  4. Hoop Netting: This method uses 3 sets of large mesh nets supported by iron hoops. The hoop nets are left out for two days after which we return and remove the fish from the nets. Read more about this technique on our fish blog.

With all of the methods the catch is identified, counted, measured and weighed, and returned except for any invasive species we may catch (fortunately no Silver or Bighead Carp have been caught!…yet…). We see a very high rate of survival of the captured fish and these are returned to the river.

The project will extend over two years, from July to September of 2016 and 2017, and will culminate in a final report providing an assessment of the Muskingum River fish community.  This information will provide a baseline for use in potential remediation efforts should the silver and/or bighead carp become established above the Devola Dam.

Technically all carp (Silver, Bighead, Grass, Common, Black, and Prussian carp, and Goldfish are the species currently established in the United States but there are at least four more – Crucian, Catlan, Mrigal and Mud Carp- are recognized as valid species) are Asian in origin.  Common Carp, by the way, are believed to have originally come from the Caspian Sea.  Back in the 1880’s the U.S. Commission of Fish and Fisheries intentionally distributed Common Carp in rail cars across much of the United States to serve as a food fish, but the idea never caught on as extensively as hoped due to the habit of wild carp to scavenge the bottom of water bodies.

Common Carp are invasive, but are considered naturalized.  They can be deleterious to stream and lake bottoms, and do impact other fish, bird, and mollusk species as well as plants, but at this point the damage has been done, so to speak.  After nearly 140 years native fish and other animals have adapted to Common Carp.  Some fishermen and environmental agents prefer to kill Common Carp whenever they are caught, in many cases simply throwing them on the stream bank to suffocate, but in truth this has little if any effect on the population since their recruitment rate is extremely high.

Silver and Bighead Carp were brought to the United States during the 1970’s and 1980’s, and escaped into the Mississippi River watershed from their state, federal and privately run facilities following extensive rains that overflowed the hatcheries.  In the Mississippi River and many tributaries they are securely established in abundances that impact native fish species and interfere with local trawling concerns.

Adult fish species that are known to be adversely affected by Silver and Bighead Carp are Gizzard Shad and Bigmouth Buffalo.  The dietary overlap of the carp with these native fishes has been shown to reduce the adults’ size and health.  In addition the high volume planktonic grazing employed by these carp is likely to compete for that food source with larvae and young-of-the-year of most other native fishes, ultimately causing a reduction in native populations.

Grass Carp are established in lakes and rivers across the State of Ohio.  Deleterious effects from this invader include removal of macrophytes (large aquatic plants) from stream bottoms with concurrent increases in turbidity.  The macrophytes provide cover and spawning habitat for many native organisms.  The carp only digest about 1/2 of the plants they eat, so the large amounts of fecal matter cause algal blooms.  The OSUM crew has caught several Grass Carp already, euthanizing and saving samples from them.

It is not known at this point what the remediation would consist of if Bighead or Silver Carp do invade the Muskingum River.  Similar to many other invasive species it would be extremely difficult if not impossible to completely eradicate them from waterways like the Muskingum River that have connections to other rivers that contain the species.  Short of completely damming the river (which carries its own set of ecological problems), or installing an electric barrier as has been done between the Illinois River and Lake Michigan, eradication would be short-lived.  It may be that the best approach would be to simply utilize the pests as a food source as has been done in Kentucky and other states, since their flesh is much more palatable than that of common carp.  If we catch any Bighead or Silver Carp (electroshocking works well for larger Silver Carp, while hoop netting is one of the best methods for Bigheads) they will be euthanized with samples taken for DNA analysis, but we really do hope that is not the case.

 

About the Author: Marc Kibbey is Associate Curator of the Fish Division at the Museum of Biological Diversity.

Sucker Bridgework

Comparative anatomies of skeletons stored at the OSU Museum Fish Division can be studied to reveal information on the sort of ecological niches a particular species occupies.  One example is the feeding niche that various sucker fish species exploit.  Based on structures of their throat teeth and the type of prey items retrieved from their digestive tract it would appear that buffalo and carpsucker species use their fine, comblike teeth for sieving their prey, while suckers with larger teeth (most redhorses, hogsuckers, spotted suckers) are said to “masticate” their soft prey, and finally those with the sturdiest teeth are able to shatter the hard shells of molluscs.

The photo below shows the anterior portion of a Silver Redhorse skeleton (OSUM 101341), with an arrow pointing to the pharyngeal tooth arch (position indicted by arrow) located at the rear of the gill basket.

SilverRedhorseSkeletonOSUMHeadshowingpharyngealteeth

There are  16 extant species of sucker fishes in Ohio’s waters.  Images of four of those species with pharyngeal tooth arches removed from some of our skeletons are shown below.

Spotted Sucker1 from Wolf Creek (Kankakee River) IN 07 01 07 by BZ

Spotted Sucker, Minytrema Melanops.  Photo by Brian Zimmerman.

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The Spotted Sucker has been reported to feed on organic fragments, diatoms, copepods, cladocerans, and midge larvae.

SmallmouthBuffalo

Smallmouth Buffalo, Ictiobus bubalus.

IctiobusbubalusSmallmouthBuffaloPharyngealTeeth

Smallmouth Buffalo suckers with their relatively delicate teeth feed on diatoms, dipteran larvae, copepods, cladocerans, ostracods, bryozoans, and incidental algae attached to bottom substrates.

ShortheadRedhorse

Shorthead Redhorse, Moxostoma macrolepidotum.  Photo by Ben Cantrell.

MoxostomamacrolepidotumShortheadRedhorsePharyngealTeeth

Shorthead Redhorse stomach contents have revealed their diet to consist primarily of midge, mayfly and caddisfly larvae.

River Rehorse from the Duck River at Shelbyville TN by Uland Thomas

River Redhorse Moxostoma carinatum.  Photo by Uland Thomas.

MoxostomacarinatumRiverRedhorsePharyngealTeeth

The River Redhorse has the sturdiest teeth of the four sucker species’ teeth shown here, so much so that they are capable of cracking the shells of bivalve molluscs and snails.

For comparison, inserted below is a photo of the molariform pharyngeal teeth from a Freshwater Drum.  The drum is primarily a carnivore, its diet comprised more extensively of bivalve mollusc and gastropod shells, while the omnivorous sucker fishes find most of their food by grazing the bottom of streams and lakes, sifting sand and gravel to find their little morsels.

drum pharyngeals downsized

 

About the Author: Marc Kibbey is Assistant Curator of the OSUM Fish Division.

Bottom Feeders

Comparative anatomy is among our oldest scientific pursuits as humans, allowing us to differentiate between delectable and deadly, and helping us to make inferences about novel organisms, the threats they might pose, and the uses to which they might be put.  Because the diversity of organisms in a museum collection exceeds that of any one location or habitat, museums are the premiere resource for comparative anatomy, allowing scientists to look at many individuals and many species, and to consider how form relates to function, evolutionary lineage, or location.

Fish Division collections manager Marc Kibbey has been using the Museum of Biological Diversity collections to study the anatomies of the feeding apparatus in suckers and minnows (order Cypriniformes).  These fish (and several others) have a complex palatal organ (PO), first described by Aristotle from a common carp, that enables them to sort out food items from the inorganic material vacuumed from the bottom of the stream. Strongly analogous to a tongue, the organ is covered with taste receptors that send information to gustatory regions of the fish’s brain. The palatal organ’s motile structure is comprised of muscle, adipose and connective tissue, and fibers.  Muscular expansion of the palatal organ pins food items to the gill arches allowing expulsion of the non-food items out of the gills.  The food is then selectively moved back to the area between the chewing pad (CP) and the pharyngeal teeth for mastication.

DooseyPOCPCatostomusoccidentalis

 

This photograph is from Michael Doosey (2011), showing the head of a Sacramento Sucker with the operculum and gill basket removed, revealing the palatal organ (PO) and chewing pad (CP).   The preparation of our skeletons uses dermestid beetles that would consume the muscular palatal organ, but the skeleton of the keratinous chewing pad remains.

CatosomusoccidentalisbyUCDavisviaFishbase

Sacramento Sucker, northern and central California.  Image from Fishbase.

The food of suckers is chewed, but not by teeth in the mouth: suckers have throat teeth instead of  jaw teeth.  These teeth are part of the gill apparatus, and differences in the shape and number of the teeth, and depth and breadth of the pharyngeal bones, help identify species and determine the types of food items they eat.  Pharyngeal teeth are constantly replaced as they are lost.

Hypenteliumnigricansgillbasket

The gill basket of a Northern Hogsucker, showing the pharyngeal teeth on the posteriormost gill arch.

Hypentelium nigricans Northern Hog Sucker

Northern Hogsucker, Mississippi River and Great Lakes drainages.  Photo by Uland Thomas.

Other clues to the biology and ecology of fishes lie in the anatomy of their swim bladders. Morphological differences in size and shape, and number of chambers in the swim bladders vary between and can help identify the species.  Size of the swim bladder corresponds to where the fish spends most of its time (suspended above or on the bottom). As with pharyngeal teeth, correspondence and consistency in the distribution of these features allows us to make inferences about the biology of new species.

ShortheadRedhorseswimbladder

Carpsuckerswimbladder

The swim bladders of the two sucker species shown here are diagnostic for their genera in that redhorse swim bladders are three chambered while carpsucker species have two chambers.  The Ostariophysi (group that includes the minnows, suckers, characins and catfishes) have larger swim bladders that enable them not only to more easily maintain position in the water column but also to more effectively detect vibrations in the water due to connection to the Weberian apparatus.  While most of the sucker species do have large swim bladders their bodies and skeletons are rather heavy, suiting them to their benthic lifestyle.

About the AuthorsDr. Marymegan Daly is an Associate Professor in the Department of Evolution, Ecology and Organismal Biology and Director of the OSU Fish Division.  Marc Kibbey is Associate Curator of the Fish Division in the Museum of Biological Diversity.

Amazing Diversity in Fish Dentition

Since the ray finned fishes are the most speciose group of vertebrates it is not surprising they exhibit such a wide range of feeding structures and functions.  Here are just a few examples of their dental arrays.

Lampreys – Lack true jaws.  Lampreys start out their life cycle with a toothless mouth suited to filter feeding, and in the parasitic forms develop several circular rows of sharp teeth used for latching onto and a radula (center of oral disk) for rasping a hole in their prey.

OSUM 104832 downsized

Sharks– teeth are triangular and razor sharp, those on the lower jaw have small serrated lateral cusps at the bases for enhanced cutting and tearing that is facilitated with strong jaw musculature and shaking motion of the head or chewing.  Sharks, unlike many of the more advanced fish species shown here, do not have pharyngeal jaws associated with their gill baskets.

Lungfish – have a tooth structure unique among the vertebrates: sturdy tooth plates called “Odontodes” that are used for grasping and crushing prey

Lungfish dentary plate (image from Nature)

Gar – rows of small villiform teeth for capturing and holding fishes in their elongated jaws while they manipulate the fish to a headfirst position for swallowing

OSUM 36915 longnose gar downsized

Bowfin – many sharp caniform, inward pointing teeth on the premaxilla, dentary and maxilla jaw bones for grasping and holding the prey (an extreme example of canine teeth in fish is shown in the African Goliath Tigerfish)

Bowfin teeth downsized

Pike – (image in previous post) the long, sharply curved caniform teeth on the dentary are a prelude to a villainous array of cardiform teeth  on the premaxillary, basibranchials, last two pharygobranchials, vomer, palatines, and glossohyal bones

Grass Carp – the heavy pharyngeal teeth of these herbivores are used for shredding algae

grass carp pharyngeal teeth

Piranha  – teeth are triangular, razor sharp, with small lateral cusps at the bases like sharks

OSUM Study Specimen Piranha Iouitos Peru downsized

River Redhorse – feed on sand-dwelling mollusks with sturdy teeth on lower pharyngeal jaws (characteristic of all ostariophysans whereas higher teleosts have pharyngeal teeth on lower and upper arches like the redear sunfish) used for crushing molluscs found in the bottom substrates

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Moxostoma carinatum pharyngeal arch

Flathead Catfish – gulp prey with large, non-protrusible mouth and hold with cardiform teeth, the largest patches of which are shown in this picture of a partial, disarticulated jaw, on the premaxillary (top of image) and anterior dentary (larger, semicircular structure at bottom of image) bones.  Gill arches show pharyngeal teeth, with pharyngeal tooth plates at the anterior, ventral symphysis of gill arches

flathead teeth downsized

Largemouth Bass – have limited cardiform teeth on the medial jaw bones, but these are complimented by a large, protrusible mouth for engulfing prey

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Freshwater Drum – All other drum species are marine, but this one is native to larger waters in the Great Lakes and Mississippi River drainages.  (1st image focused on the anterior aspect of the jaw) Note the incisor-like anterior teeth on the anterior dentary for nipping prey off substrates, the molariform teeth on the heavy glossohyal bones, (2nd image focused on the posterior aspect of the jaw) the sturdy pharyngeal teeth on the gill arches for capturing and shredding prey, and the molar-like teeth on the pharyngeal tooth plate for crushing mollusk shells

drum jaw downsizeddrum pharyngeals downsized

Ocean Pout – like many molluscivores have strong conical dentition on the anterior portion of their jaws for plucking mollusks from surfaces, and flattened, molariform teeth in marginal or pharyngeal jaws

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X-ray from Canadian Museum of Nature

Triggerfish (incisor-like dentition), Pufferfishes (teeth fused into parrotlike beak) – have powerful jaws to remove invertebrate prey (sponges, ascidians, coelenterates and chitons) from surfaces

puffer mouth downsized

 

About the Author: Marc Kibbey is Assistant Curator of the OSUM Fish Division.