Archive for the ‘Ichthyology’ Category

The Sand Tiger Shark (Carcharias taurus)–a Palaeocene Age Survivor

June 1, 2022

The sand tiger shark is the oldest still extant species of shark, having existed for at least 65 million years. Some sources claim it first evolved during the Cretaceous Age and lived with the dinosaurs 72 million years ago, but according to the scientific literature I can find, the oldest fossils of this species were found in the Cannonball Formation located in the Dakotas, a region that was formerly undersea, and species from fossil sites here date to the Palaeocene–the era immediately following the extinction of the dinosaurs. This is still impressive longevity for a species. By comparison modern man (Homo sapiens) has existed for about 200,000 years. The sand tiger shark should not be confused with the similarly named tiger shark (Galeocerde cuvier). Although sand tiger sharks occasionally bite people, they are not maneaters. Tiger sharks definitely are maneaters. The scientific name for sand tiger shark may also cause confusion. Carcharias taurus means bull shark in Latin, but the commonly named bull shark (Carcharhinus leucas) is also a different species.

Sand tiger shark, the oldest still extant shark species.
The sand tiger shark should not be confused with this species–the tiger shark. The former is not a maneater, but the latter is.

Sand tiger sharks can reach lengths of just over 10 feet long, and they feed upon fish, squid, and shrimp. They are known for preying on stingrays and smaller, slower sharks near the sea bottom at night. They rest during the day. They are the only species of shark to gulp air. This helps them retain buoyancy, so they don’t have to constantly swim like other kinds of sharks. The shark pups are born alive, the survivors of cannibalistic embryos attacking and eating each other while still inside their mother. Sand tiger sharks range in shallow coastal waters along the Atlantic coasts of North America and Europe. They also occur off the coasts of China, Japan, Australia, and South Africa. Scientists believe they were overfished to extinction in the Mediterranean Sea where they used to live.

Fossil sand tiger shark teeth.
Fossils from the Cannonball Formation. The majority of fossils from this site are sand tiger shark teeth. Image from the below reference.

Paleontologists found fossils of 22 species in the Cannonball Formation. This region was under ocean water until the end of the Palaeocene 55 million years ago. Sand tiger shark teeth are the most common fossil specimens found in this formation. Sand tiger sharks may be the oldest still extant species of shark, but the still extant Hexanus genus is even older. The Hexanus genus includes the gill sharks. Some species of extinct gill sharks lived 190 million years ago during the Jurassic.


Cvancara, A.M.; and Hogansan, J.W.

“Vertebrates of the Cannonball Formation (Palaeocene) in North and South Dakota”

Journal of Vertebrate Paleontology 13 (1-23) 1993

Unique Fish of the Yucatan Peninsula

July 23, 2021

Underground rivers flow through the limestone bedrock underneath the Yucatan peninsula of Mexico. When a river enters a cavern it flows in a circular pattern, eroding the walls into a circular shape. The roofs of these caverns eventually collapse, creating a small bucket-shaped lake known locally as a cenote. There are almost 20,000 cenotes on the Yucatan peninsula, and they host many unique fish species found nowhere else on earth. A recent survey of 4 cenotes captured 1,350 fish including 11 species from 5 families. The cenotes studied were small and deep–less than 2 acres wide but over 30 feet deep.

The most common species found in this study were mosquito fish from the Poeciliid family. Cichilids were also common, most notably a beautiful fish, the yellow jacket cichlid. This fish is a popular game fish, reportedly with a good flavor. The yellow jacket cichlid has an interesting habit–it feigns death and preys on smaller fish that attempt to scavenge it. Colorful tetras, popular aquarium fish, live in cenotes, and they are preyed upon by the pale catfish, the top predatory fish in the studied cenotes. Scientists found blind swamp eels in these surveyed cenotes. Blind swamp eels are found throughout underground cave systems in the region and have no need for sight. Although some cenotes are connected to the ocean through underground passages, scientists found little marine influence on them. Instead, zooplankton and insect abundance along with phosphorus concentrations have a greater influence on fish populations.

View from inside a cenote. There are almost 20,000 of these geological features on the Yucatan Peninsula and they host fish species found nowhere else in the world. Photo from
Yellow Jacket Cichlid. A beautiful fish that is popular for catching and eating.
Blind swamp eel.
Pale catfish.

The Yucatan Peninsula was also home to an unique mammalian fauna during the late Pleistocene. Cenotes inundated by sea level rise preserved the remains of many species, including a species of giant ground sloth and a species of peccary found nowhere else. 4 complete human skeletons dating to the late Pleistocene were discovered in a cenote that is now below sea level. (See: yucatan peninsula | Search Results | GeorgiaBeforePeople ( )


Camargen-Guerra, T; L.K. Escalera Vazquera, L. Zambrano

“Fish Community Structure Dynamics in Cenotes of the Biosphere Reserve of Sian Kaan, Yucatan Peninsula”

Revista Mexicana de Biodiversidae

Pleistocene Whitefish (Coregonus clupeaformis)

April 17, 2021

Fish have an amazing ability to replenish and increase their populations. Lake whitefish, a species related to salmon and trout, can lay between 8,000-130,000 eggs. During Ice Ages 90% of their present day range was covered by glaciers, making it uninhabitable for them. Yet, in less than 12,000 years they recolonized this enormous territory. The reproductive ability of this species outpaced the population of predatory fish and birds that fed upon them. Scientists used a study of genetics to determine modern day whitefish descend from 2 different refugial populations that clung to survival during the Last Glacial Maximum. 1 population survived in Beringia–the area of Alaska and the Yukon that remained free of glacial ice. They may have survived in lakes now located near Nahanni National Park. The other population occurred in the Missouri/Mississippi River Drainage just south of the Laurentide Ice Sheet. Following the retreat of the Ice Sheet, lake whitefish populations exploded in the newly formed Great Lakes and managed to swim their way into lakes all over Canada. Whitefish are a cold water species and probably didn’t ever live far from Ice Age glaciers.

Map of present day range of lake whitfish. Most of this range was under glacial ice during Ice ages.
Lake whitfish.

Lake whitefish average 4 lbs. as adults, though the record for a rod and reel catch is 15.5 lbs. They spawn during fall, winter, and spring. Their diet consists of snails, clams, and insects. There are 2 ecotypes of whitefish that do not interbreed: the normal population that inhabits the bottom region of lakes and the dwarf population that swims in the upper layer of open water. Commercial fishermen net whitefish, and they are a popular food fish in cities and towns along the Great Lakes, but I can’t remember if I ever had the opportunity to try them when I lived in Ohio as a boy.


Foote, C.; J. Clayton, C. Lyndsay, and R. Bodaly

“Evolution of Lake Whitefish (Coregonus clupeaformis) in North America during the Pleistocene: Evidence for a Nahanni Glacial Refuge in the northern Cordilleran Region”

Canadian Journal of Fisheries and Aquatic Services 49(4) April 2011

McDermid, J., J. Riest, R. Bodaly

“Phylogeography and Post Glacial Dispersal of Whitefish ( C. clupeaformis complex) in Northwest North America”

Advances in Limnology 60 Jan 2007

A Study of My Seafood Consumption during 2020

January 1, 2021

90% of the seafood consumed in the U.S. is imported, and most of that is farm-raised.  This is a shocking statistic, considering how abundant fish were in American waters when Europeans first colonized the continent.  I was curious about my own seafood consumption, so I kept a tally of the fish and shellfish I ate in the year 2020.  I tried to avoid the Heisenberg Effect defined as the act of measurement altering the phenomenon under investigation, but I can’t rule out my subconscious influencing the results.  Nevertheless, I usually eat seafood once a week, and I believe this is a fair account of my average year’s seafood consumption.  The following paragraph is the result of my study.

I consumed seafood 76 times during 2020 or about 6.9% of my meals.  The tally is shrimp-13, tilapia-10, salmon-9, catfish-8, tuna-7, crab-4, croaker-3, sardines-3, oysters-3, trout-3, herring-2, crawfish-2, flounder-2, lobster-1, eel-1, Pacific cod-1, and unknown-1.

Figure 2 from Presence of Pacific white shrimp Litopenaeus vannamei (Boone,  1931) in the Southern Gulf of Mexico | Semantic Scholar

Pacific white-legged shrimp–small, medium, and large.  I like the largest ones because it takes less work to peel and clean them.  Along with tiger prawn shrimp these are the most common species found in the supermarket.  90% of shrimp consumed in the U.S. come from shrimp raised on farms in the Far East.

Shrimp is the most popular seafood consumed in the U.S. and 90% of it is imported.  It was my single most consumed seafood item as well.  Most of the shrimp consumed in the U.S. is raised on farms in Indonesia, Vietnam, and China.  30% of the world’s production is in Asia, and 54% is in Latin America.  Texas is where most shrimp are farmed in the U.S. The 2 most common species raised are the Pacific white-legged shrimp (Litopannaeus vannamei), and giant tiger prawns (Penneus monodon).  Some claim wild caught shrimp from the Gulf Coast are sweeter, but I think they taste like gasoline because of all the oil spills there.  It takes 3-6 months to raise a shrimp from egg to saleable adult, and shrimp farmers cut off the eye-stalks of the females to increase egg production.

Nile Tilapia (Oreochromis niloticus) - Species Profile

Nile tilapia (O. niloticus).  This was the 2nd most common seafood item I consumed during 2020.

The species of tilapia (Oreochronis sp.) raised by farmers originated in Africa.  5 species of tilapia now live in southeastern North America where they have become an invasive species, but they can’t survive in waters below 50 degrees F and will probably not expand out of the region.  An adult can be raised from a fingerling in 6-7 months on a cereal diet, making them a clean fish to produce.  Indonesia, Egypt, Brazil, and the Phillippines lead world production.  I notice the ones I eat come from Ecuador.

Salmo Salar - Salmon Wiki

Atlantic salmon came in 3rd.  All salmon sold in grocery stores (even those labeled as wild salmon) are farm-raised.

Norway, Chile, Scotland, and Canada are the leading world producers of salmon, and the vast majority are Atlantic salmon (Salmo samar). There is no such thing as wild caught salmon in grocery stores.  Fish labeled as “wild caught” are actually wild fish driven into pens and fed just like farm-raised salmon.  Trout sold in grocery stores are also farm-raised.

Channel Catfish

Channel catfish was my 4th most consumed seafood.  This is the only species I ate that mostly originated in the U.S.

In North America channel catfish (Ictalurus punctatus) are raised in the Mississippi Delta (including Mississippi, Alabama, and Arkansas) and California.  Still, the world produces 3 times more catfish than the U.S.  The American catfish lobby legally forced grocery stores into labeling Chinese-raised catfish as basa in order to reduce competition.  How silly?  A consumer purchasing basa is actually buying a species of the shark-finned catfish (Pangasiidae sp.).  1 acre of water can produce 300 pounds of catfish–a more efficient production of protein than any chicken farm or cattle ranch can match.

My consumption of wild caught fish is low, and so is the quantity and quality offered in the average supermarket, probably because the oceans are so overfished. The croaker I ate tasted like fish that had sat on a fish market counter for 3 days before they stuck it in a box and froze it. Tuna was the only significant component of wild caught fish in my tally, but scientists are experimenting with tuna farms.  In the future farm-raised tuna might be found in grocery store fish cases alongside farm-raised shrimp, tilapia, salmon, and catfish.

Pleistocene Amberjack (Seriola dumerili)

October 17, 2020

I watched Food Paradise with my wife the other night, and we heard the chef of a restaurant in Florida say grilled amberjack was the house specialty. My wife asked what an amberjack was, and I told her it was a fish. She knew that, but she wanted to know what kind of fish an amberjack was.  This blog article is for her.

The greater amberjack is a large predatory fish found in warm ocean waters around the world.  They swim in schools located 60-200 feet deep, but they prefer coastal waters studded with manmade and natural structures such as shipwrecks and rocky outcrops.  Amberjack migrate to those structures to spawn, so their small offspring can hide in the crevices from larger fish.  Greater amberjacks reach a length of 6 feet long and can weigh up to 40 pounds, and they prey upon fish, squid and crustaceans.  During summer they expand their range north, and some populations migrate toward shore.

Greater Amberjack | NOAA Fisheries

Greater amberjack.

Amberjack Fish Culinary Profile - Chefs Resources

Greater Amberjack range map. They prefer deep waters near the coast.

As far as I can determine, not a single fossil specimen of amberjack has ever been found.  None are listed on the paleobiology database.  However, amberjack are a deep water fish and potential fossil locations are likely inaccessible.  Amberjacks belong to the Carangidae family which includes jacks and pompano, and they’ve existed for millions of years.  Genetic evidence suggests amberjacks from the Atlantic colonized the Mediterranean Sea during the Late Pleistocene after an existing population there had already split into 2 clades.  The population of amberjacks in the North Atlantic recently diverged from the population in the Gulf of Mexico.  Closure of the ancient Tethys Sea, and the rise of the Isthmus of Panama caused speciation in the Seriola genus.

Amberjack Recipes - Florida Go Fishing

Grilled amberjack. Some specimens of amberjack can be toxic.

Amberjack living in tropical waters can accumulate toxins in their flesh by eating smaller reef fish that have been exposed to dinoflagellates responsible for red tides. 

Fish is my favorite food to charcoal grill.  I think fish flesh absorbs the charcoal grill flavor better than any other protein.


Bobie T. ; et. al.

“Two Seas, Two Lineages: How Genetic Diversity is structured in Atlantic and Mediterranean Greater Amberjack Seriola dumerili: Russ 1810 (Perciformis, Carangidae)”

Fisheries Research

Swart, Belinda

“The Evolutionary History of the Genus Seriola, the Phylogeography and Genetic Diversity of S. Lalandi (Yellowtail) Across its Distribution Range”

PHD Thesis Stellenbosch University 2014

Tuna- The Superfish

June 24, 2020

Most people think of tuna as just some fish in a can that is an ingredient in tuna salad.  They don’t appreciate what a spectacular animal it is.  Biology books state that fish are cold-blooded, but tuna are an exception to this rule.  Tuna are actually a warm-blooded fish, and this physiology enables them to swim at ultra high speeds of up to 47 mph.  That is faster than most boats.  However, their warm-blooded physiology has a greater temperature range than those of mammals and birds.  Their blood temperatures do vary, while mammal and bird temperatures generally stay constant, unless they are sick.  The video below shows off the impressive speed of this animal.  They swim with dolphins for protection against sharks, explaining why dolphins can get caught in nets intended for tuna.


Tuna are large predatory fish that can swim up to 47 mph.

There are 15 species of tuna within 5 genera including the Allothonnus (thunder tunas), the Auxil (frigate tunas), Euthynnus (little tunas), Katsunnus (skipjacks), and Thunnus (true tunas).  Bonitos are considered a sister species to the tunas, and both are part of the mackerel sub-group.  4 species of tuna overwhelmingly make up the tuna found in supermarket cans and at fish markets and sushi restaurants.  These include bluefin, yellowfin, skipjack, and albacore.

Tuna did not become a popular food fish until well into the 20th century, but now every grocery store in the U.S. stocks tuna.  It doesn’t seem likely to me that this can go on forever.  Eventually, wild tuna populations will become too depleted to support this fishery.  The future of tuna remaining a staple in our diet is aquaculture, but tuna fish farming is in its infancy.  Some Japanese have had experimental tuna fish farms for decades, but the 1st tuna farm in America just opened business last year in San Diego.  Tuna fish farming, unlike tilapia, catfish, and salmon aquaculture, has a long way to go.

There is evidence from Indonesia that humans caught tuna as early as 42,000 years ago. (See: ) It’s surprising some primitive people had deep sea fishing technology that early, though tuna swam closer to shore during the Pleistocene because land extended over the continental shelf and deep waters were located closer to the coast then.

Albacore - Wikipedia

The most common species of tuna found in a can–albacore.

Giant Bluefin Tuna Sells for $3.1 Million in Tokyo | Fortune

500 pound tuna are worth over 3 million dollars to sushi chefs.

1 of my favorite summer dishes is tuna noodle salad and it is very easy to make. Mix a 12 oz package of tuna with the juice of a lemon.  Add a 16 oz box of cooked macaroni, mayo to taste, a can of peas, chopped celery, chopped Vidalia onion, and couple of chopped hard boiled eggs. Stir it up and serve it warm or cold from the refrigerator.

This is my tuna noodle salad.  It’s great warm or straight out of the refrigerator on a hot summer’s day.

Don’t Believe it when People or Books Refer to Some Species as Trash Fish

January 24, 2020

I often found it hard to believe books or people who refer to some species of fish as trash. I think some reject eating certain fish based on their ugly appearance or difficulty in cleaning and dressing.  However, I don’t get to fish much because my wife is disabled, and I’ve had to give her 24 hour care for 24 years.  I never had the chance to prove these claims wrong.  Recently, I discovered a youtube channel produced by a man who does just that.  He has videos of hundreds of outdoor recipes including a series entitled “Fish: Trash or Treasure.”  His youtube channel is The Backwoods Gourmet.

In the first episode I watched he prepared 2 species of saltwater catfish by frying them with a cornmeal coating.  Many books about fishing refer to them as “trash.”  Though they were a “pain to clean,”  the backwoods gourmet discovered hardhead catfish tasted just like freshwater catfish, and sailfin catfish tasted like sea trout.  Whoever labeled them as “trash” were wrong.  In another episode he prepared chain pickerel.  This is the 2nd species of fish I ever caught.  I was 10 years old, visiting my grandfather in Inverness, Florida, when he showed me how to set a pole out over night.  I jumped up and down in excitement upon awakening in the morning to find a pickerel on the line.  But my grandfather told me we couldn’t eat it because it was too bony.  The backwoods gourmet was able to filet 2 boneless backstraps from a chain pickerel, and he pronounced it delicious.  John Lawson, an early settler of North Carolina, once found 300 chain pickerel in his fish trap circa 1710.  (See: )

The backwoods gourmet tried bonita, a species of tuna thought of as trash.  He blackened some and smoked the rest, and said it tasted as good as restaurant tuna.  He also fried black drum, and sheepshead roe.  The black drum was good, and he enjoyed the creamy sheepshead roe.  I boiled freshwater bream roe and discovered they tasted just like bland chicken eggs.  But to me, store bought caviar pretty much tastes like fish guts and needs to be mixed with cream cheese to get it down.

Sea robins are a bizzare-looking fish that the backwoods gourmet fileted and sautéed in garlic butter.  He called it “amazing.  Another really strange-looking fish he tried was remora.  This interesting species has a sucker on the top of its head that attaches to a shark’s body.  When the shark is feeding, the remora detaches itself and feeds on the scraps.  The backwoods gourmet said they tasted like red snapper.

Backwoods gourmet shows how to clean and cook a remora fish.

In another episode the backwoods gourmet prepares long-nosed gar.  This species was a favorite of the American Indian, and it is still popular in Cajun cuisine.  He had to use a pair of snippers to cut through the thick armor.  He said it tasted like alligator.  In the entire series the backwoods gourmet found just 1 species that he labeled trash–the ladyfish.  It tasted good but was just too full of bones to eat.

There are a couple additional aquatic animals the backwoods gourmet cooks on his youtube series.  Frog legs are not all that unusual and are considered a delicacy in France.  That’s why the French are sometimes known as “frogs.”  He turned soft-shelled turtle into grilled kabobs and said they were chewy and tasted like chicken.  The 1 time I cooked turtle, I was able to make the meat tender by pounding it with a meat mallet, and I thought it tasted like lobster.  On the 4th of July he staged a turtle egg-eating contest.  The white on a turtle egg never gets hard no matter how long it is boiled.  The 3 adults who tried the turtle eggs liked them but a kid almost gagged on it.

Pleistocene Puffer Fish (Spheroides maculatus)

June 16, 2018

Pier fishermen often catch what many consider to be “trash” fish.  Stingrays, eels, dogfish, and puffer fish are common in shallow coastal waters during the summer and readily take bait.  Although fishermen usually throw them back in the ocean, they are all good to eat.  Pieces of stingray wings cut with a cookie cutter are used to make mock scallops.  Eel is a delicacy I have enjoyed.  Dogfish, a small species of shark, really does taste like chicken when fried. During WWII when rationing made meat scarce, fishermen caught hundreds of thousands of pounds of puffer fish off Long Island and sold them in New York City fish markets under the name “sea squab.”  However, an important cautionary note needs to be made about consuming puffer fish–its flesh is toxic in some regions.  From researching this topic online, I’ve determined puffer fish caught from North Carolina to Massachusetts are safe to eat, but puffer fish caught from Florida south to the tropics are deadly.  It is against the law to consume puffer fish caught off Florida’s coast because it contains so much saxitoxin.  I have not been able to determine whether puffer fish caught in the border region in between Florida and North Carolina are safe, so I wouldn’t chance it.


Video of a man cleaning puffer fish caught off the North Carolina coast.  It yields a piece of fish about the size and shape of a chicken drumstick.

Image result for illustration of puffer fish before and after it blows up

Illustration of puffer fish before and after it blows up.

The northern Atlantic puffer fish, also known as a blowfish, is a member of the Tetraodontinidae family which includes 29 genera and 191 species.  Most of these species occur in tropical waters and are toxic.  The family includes the famous fugu fish served in Japan where specially trained chefs dress them in a way that makes them safe for human consumption.  Toxins are heavily concentrated in the liver and gonads.  Puffer fish inhale air or water when threatened, and they have prickly spines on their scales.  This makes them tough for predators to grasp or swallow.  Ospreys are unable to grab puffer fish.  This defense mechanism has helped this family survive for millions of years.  Definitive fossil evidence of species in the Tetraodontinidae family has been unearthed from strata dating to the Cretaceous over 100 million years ago, and some specimens that may belong to this family were found in Triassic deposits.

The northern puffer fish evolved to live in cooler waters than its tropical cousins.  Cooler ocean currents began to expand in circulation early during the Pliocene when Ice Ages began to occur.  This may be when the northern puffer fish diverged from the southern puffer fish (S. nephulus) which reaches its northern range limit off the coast of north Florida where the 2 species overlap.  In this area northern puffer fish inhabit deeper waters to avoid competion with S. nephulus.  Northern puffer fish move into shallow waters over most of the rest of their range during summer but move to deeper waters when the water temperature seasonally cools.  This pattern may have been disrupted following Ice Age Heinrich Events when  the Gulf Stream shut down due to influxes of glacial meltwater.  There is no known Pleistocene-aged fossil evidence of puffer fish, and scientists have not yet studied the Tetraodontinidae family genome.

Puffer fish prey on crustaceans (schools of puffer fish gang up on blue crabs), molluscs, worms, and sponges; and they consume seaweed and algae. The species of algae they eat in warmer waters is toxic, and this is how they acquire their toxicity.  This explains why the same species is safe to eat when caught from cold waters but toxic from warmer regions.  There is no antidote for this kind of nerve poison.  It shuts down the victim’s nervous system.  A victim may recover in a few hours or days or they may die from suffocation while wide awake as their lungs and heart cease to operate.

Banks, S.; and Anthony Pachee

“Biology and Fishing Data on Northern Puffer (Spheroides maculatus)

NOAA Report 26 1961

Gibbon, Euell

Stalking the Blue-eyed Scallop 

David Mackay Publishing 1964

Fish Nest Associates

May 6, 2018

The bluehead chub (Nocomis leptocephalus) is a keystone species in piedmont and mountain rivers and streams of southeastern North America.  Dozens of species of shiners spawn and lay their eggs in bluehead chub nests.  Without the existence of bluehead chubs most of these species would probably become extinct.  Bluehead chubs and shiners are members of the minnow family, known scientifically as the Cyprinidae, and bluehead chubs are 1 of the largest minnow species, growing up to 8 inches long.  Bluehead chubs make large gravel nests and aggressively protect their young.  They bury their eggs with large pieces of gravel and in the process bury and protect the eggs of other minnow species.  A complex ecosystem inhabits bluehead chub nests. Many macroinvertebrates live in bluehead chub nests alongside the minnow eggs.  Snails, clams, and the larval stages of dragonflies, dobsonflies, caddisflies, and beetles use the bluehead chub nests for shelter.  Salamanders and darters prey on the invertebrates entering and exiting the nests.  Scientists believe shiners and bluehead chubs both benefit from the congregation of eggs and hatchling fish, referring to the relationship as mutualism.  The great abundance of eggs from several different species dilutes the losses to predators, and more young of each individual species survives.

Image result for blue chub range map

Bluehead chub range map.

Bluehead Chub

Bluehead chub.

Image result for rainbow shiner

Rainbow shiner (Notropis chrosomus).  Some shiners can get quite colorful.

Many other species of fish associate in the same nests.  Rough shiners (Notropis baileyi), saffron shiners (N. rubicroceus), and greenhead shiners (N. chlorocephalus) spawn in creek chub nests.  Redfin shiners (Lythurus umbratalus) spawn in green sunfish (Lepomis cyonellus) nests.  All of these associations result in increased reproductive success for both species.  Some shiners will use central stoneroller nests, but prefer chub nests and will move their spawning activity to bluehead chub nests, if they become available.

The evolution of fish nest association must be very ancient.  It seems likely the host fish evolved first, and the species of fish using the host’s nest lost their ability to make their own nests when they came into contact with the larger  host species because the host could build bigger nests that offered more protection.  Host species are usually larger and better able to defend the nest than the smaller minnows, but they benefit too from the sudden population explosion of potential food for predators that might otherwise eat their hatchlings.


Johnston, Carol

“Nest Associate in Fishes: Evolution of Mutualism”

Behavioral Ecology Sociobiology 35 1994

Swartwout, M.; F. Keating, and E. Frimpas

“A Survey of Macroinvertebrates Colonizing Bluehead Chub Nests in a Virginia Stream”

Journal of Freshwater Ecology 2016

Pleistocene Fish of the Tennessee River System

December 28, 2017

Many Italians like to celebrate Christmas Eve with the feast of the 7 fishes.  I’m not Italian, but I like to eat seafood during the holiday season too, though my immediate family is small, and we enjoy the feast of the 2 fishes.  I wonder what species would’ve composed a feast of fishes for Paleo-Indians when they first entered the Tennessee River Valley.  Fish populations were much higher in the pristine pellucid waters of all southeastern rivers before man began destroying the environment, but the composition of species is poorly known because fish remains that old are rarely preserved.  A new study of fish remains excavated from Bell Cave partially unveils this mystery.  Bell Cave in Colbert County, Alabama overlooks the Tennessee River and floods periodically stranded fish inside the cave from ~13,000 calendar years BP-~30,000 calendar years BP.  Predators carried fish into the cave as well.  Scientists collected vertebrate bones from this cave between 1984-1987, but no one identified the fish remains and published the data until 2016.  This study also catalogued fish remains from other sites near the Tennessee River including Baker Bluff Cave, Beartown Cave, Guy Wilson Cave, Cheekbend Cave, Dust Cave, Little Bear Cave, Appalachian Caverns, and Saltville.

Image result for Tennessee River map

Map of the Tennessee River.

The authors of this study identified 41 taxa and 38 species that lived in the Tennessee River during the late Wisconsin Ice Age.  The number of species they identified is a subset of the population that actually swam in the river because, by chance, many species just never got trapped in the cave or were too decayed to be identified.  This is especially true for smaller species.  Almost all of the species they identified still live in the Tennessee River system today, but there are 3 exceptions.  Northern pike (Esox lucius) no longer naturally occurs this far south, although man has introduced this species into some bodies of water.  (Muskellunge, a related species, surprisingly still occurs in the Tennessee River.  Fossil evidence suggests they were fairly common here during the Ice Age.)  Northern madtom (Noturus stigmosis), a small species of catfish, also no longer occurs this far south. The harelip suckerfish (Moxostoma lacerum) became extinct during the late 19th century.  This species required very clear water with gravel bottoms, but deforestation and agriculture caused erosion that muddied its spawning grounds.  Pleistocene rives were clear enough for this species.

Image result for northern pike

Northern pike.

Image result for noturus stigmosis

Northern madtom.

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Harelip sucker.

Rock bass were the most commonly represented fish from the Centrarchidae family catalogued in this study, but curiously they found not a single specimen of sunfish.  Bluegill sunfish are 1 of the most common fish in the Tennessee River today because they thrive in manmade reservoirs, but that kind of environment was rare before man began impounding rivers.  Sunfish probably lived in oxbow lakes that weren’t close enough to caves where their remains could’ve been preserved.

A Paleo-Indian trapping fish in the Tennessee River could’ve enjoyed a feast of 7 fishes consisting of sturgeon, northern pike, walleye, sauger, freshwater drum, bullhead catfish, and eel.  These were probably the best tasting fish available to them then.


Jacquemin, S.; J. Ebersole, W. Dickinson, G. Ciampaglio

“Late Pleistocene Fishes of the Tennessee River Basin: an Analysis of a Late Pleistocene Freshwater Fish Fauna from Bell Cave (site Acb-2) in Colbert County, Alabama”

Peer J 2016