Bowfin Science

What makes a bowfin tick? (we know what makes him ticked off!) How is it that she has remained virtually unchanged for 150,000,000 years? This page, created with the help of Michael S. Hedrick, Ph.D., attempts to answer some of these questions.
Professor Hedrick teaches vertebrate physiology in the Biology Department at California State University, Hayward. His graduate work on breathing patterns in Amia calva led to his current research on neural control of respiratory rhythm in vertebrates.

Visiting Professors and Grad students, feel free to send in your Bowfin related research or information. We are always interested in furthering our bowfin education. If we can be of any assistance in your bowfin research, let us know, and we'll try to help.

The Colors of Bowfin Angling

Far from ugly, the bowfin sports some of the prettiest colors seen in freshwater fish. Thanks to HenryV for the idea to point this out.

melanistic bowfin Bee K with a rare melanistic bowfin and John V with an equally rare albino. Bee caught the all-black fin in Minnesota. It wasn't until after he released it that he realized he had caught a once-in-a-lifetime fish. John landed his once-in-a-lifetime white fin in New Jersey.

As the water gets colder, the Bowfin develop these amazing reticulated patterns that look like a cross between those you see on a Tiger Musky and a chain pickerel. HenryV, NC, 12/12/07

Sandra's Texas bowfin, a spawning male, is prettier than just about any other freshwater fish.




Copper/Red Tail



March 2010 - Bowfin Age and Growth Study!

I am a fisheries biologist with the Virginia Department of Game and Inland Fisheries and I collected some data a couple years back on Bowfin in Virginia. The data is from a couple of rivers (Blackwater and Nottoway) in SE Va, and we saw some pretty interesting trends. Thought you might be interested.
Eric Brittle
Region 1 Fisheries Biologist
Va. Department of Game and Inland Fisheries

Finners - that "little" 24 inch fin is likely 6 years old!

March 2010 - Bowfin Harvest and Age Studies!

Dr. Michael C. Quist, of Iowa State University's Department of Natural Resource Ecology and Management sent these two studies which he co-authored. The first is a study of "Population dynamics and potential management of bowfin (Amia calva) in the upper Mississippi River". The study suggests that while overfishing is not currently a problem in the locations studied, if limits are imposed to prevent overfishing a 25" minimum is the target. This study also mentions the Bowfin Anglers' Group favorably!

The second, "Precision of Hard Structures Used to Estimate Age of Bowfin in the Upper Mississippi River" looks at various ways to determine the age of a bowfin because, "precise age and growth information is needed to better understand and manage bowfin populations."
Thank you Dr. Quist for furthering our knowledge of bowfin!

July 2009 - Bowfin As Oranges!

I am a fisheries biologist in Ohio who works for the Ohio Sea Grant College Program and OSU's biological field station, F.T. Stone Laboratory. A member of the Ohio Game Fishing forums posted a link to your site. What a joy! I've taken a great many bowfin on rod and reel, but even more in fyke nets, some beasts approaching 2.5 feet.

There is one fascinating aspect of bowfin I didn't see referenced on your science page. Bowfin can synthesize ascorbic acid in their kidney. That's right, they can manufacture their own vitamin C! Wiley Interscience Abstract The author, Konrad Dabrowski, is a professor here at OSU.

Eugene B, 07/04/09

April 2009 - Bowfin Aggression

I'm wading a heavily vegetated area of the swamp. Bugs were eating me alive. I see a fin stick his head up for air so I ease over that way. After about 10 minutess he came by me at a good pace. I lost track of him after that. Then, all of a sudden, he jumps up and bites my leg! Scared the heck out of me. I started yelling; I didn't know what just happened. I looked down and he's still there. He didn't just bite my waders and run off, he was trying to pick a fight!

I put my Senko in the water and he hit it instantly. He got away that time. A moment later I look and he's flanking me. He's looking straight at me with his mouth wide open and gills stuck out. I dropped my Senko on him again and this time I landed him.

Soon after I see a black mass moving through the water. It was a wad of baby bowfin. LOL, now I get it! I read the males protect the nest but never thought a 3.5 lbs fish would attack a 200lbs 6ft person!

I placed him back on the bed. I'll retire that spot for the year and hopefully next year I'll have a sweet bowfin honey hole. Joe and I found at least 4 nests with bowfin lurking by acting just like this guy. What an awesome fish!!

MikeS, 04/20/09

January 2007

Here is a paper I didn't see on your Science page. The Minnesota DNR had an interesting idea regarding use of bowfin to control stunted panfish, but it didn't work as well as they hoped.
Take care,
Dan O, 01/30/07
Postdoctoral Research Associate
Department of Wildlife and Fisheries
Mississippi State University

Effectiveness of Bowfin as a Predator on Bluegill in a Vegetated Lake

Neal D. Mundahl, Christina Melnytschuk, Deena K. Spielman, Jason P. Harkins, Kate Funk, and Andrew M. Bilicki
Department of Biology, Winona State University Post Office Box 5838,
Winona, Minnesota 55987-5838, USA

Abstract.—Adult bowfins Amia calva were reintroduced (initial density approximately 32 fish/ha) into Lake Winona, Minnesota, from 1984 to 1986 to evaluate their effectiveness in controlling overabundant, stunted bluegills Lepomis macrochirus and other sunfishes (centrarchids) in a system with extensive macrophyte beds. Bowfin catch rates (trap nets, gill nets and electrofishing) declined rapidly after reintroductions ended in 1986. Catch rates and growth rates of bluegill and black crappie Pomoxis nigromaculatus have not changed since bowfin reintroduction. In 1992, only adult bowfins (average age, 10 years; average weight, 2.4 kg) were captured in Lake Winona, and they were concentrated in or near dense macrophyte beds. The final population estimate for bowfin in the west basin was 114 fish (3.17 fish/ha). Captive bowfins exhibited no size selection when feeding on sunfish and consumed on average less than 5 sunfish/24 h. Bowfin consumption rates declined by 80% when the density of artificial vegetation exceeded 500 stems/m2. Bowfins preferred both fathead minnows Pimephales promelas and virile crayfish Oronectes virilis over sunfish in prey choice trials. Lack of natural reproduction by bowfins in Lake Winona, their rapid decline in numbers after stocking, and their low rate of sunfish consumption may explain why bowfins apparently have been ineffective in controlling the lake’s bluegill population.
© 2007 American Fisheries Society

June 2005

This exchange came from the forum and I thought this was the best place for it. Although not Science in the strictest sense, it is a good observation of bowfin spawning behavior:

My son and I were out fishing in a pond and he said he saw a big fish swimming close to shore so I looked and saw it was a big bowfin. After about 10 minutes passed it just rolled over and was upside down, just motionless, but was breathing a little. It was in about a foot of water so I cast to it with the #6 hook that was on my line. It bit down on it once I put it up to his mouth. It was a big dang fish. I guess it was dying but what an easy catch that was. I threw him out to deeper water and that was that. It was about 20 inches long and pretty heavy (no scale). It was bleeding a little and some of its scales were a little white towards the back part. Thanks for any thoughts on this!!

Interesting....Not sure what part of the country you're in, but it's possible this may have been a post-spawn female. Although I have never seen one actually go belly-up before, I have seen many spawns before and they are a bit rough on the females at times. The smaller males often bite down on the fins of the larger females to hold them in position as they lay their eggs. Often the females will slip out and the males will again bite down on the nearest fin/sometimes the tail to keep the females in the nest. This will often cause bleeding from the fins and tail and cause them to turn white after some time has passed. When the spawn is complete, the females often leave the area very slowly and erratically. Almost exactly as you described, until the belly-up part that is. Perhaps it was just a post-spawn female, or just a fin who's time had come. Not exactly sure, but interesting indeed.
CJ 06/07/05

EPA Mercury Advisory

On 10/15/04 Dusty, an employee of the NY DEC sent the following:

Just a note: The US EPA just released a report on mercury in fish, and Bowfin were head and shoulders above any other fish. This is basically the exact work I've been doing in New York for the last 2 years. The two things to look at are the technical memorandum and the mean tissue mercury concentration graph.
Dusty E

The report recommends no more than one 8-oz bowfin meal per month for the average 150lb adult (so I get a pound!). They advise that consumers should, first and foremost, consider any local advisories.

Bowfin fossils in Maryland

We received this update on 9/7/04. Stay tuned!

This is in regards to the partial fossil Amiid found in the Saint Mary's formation in Calvert county Maryland. Lance G looked over some of the disarticulated remains on 9/3/04. He confirmed that it was an Amiid but could not say what species at this moment. Unfortunately the head region was the only portion of the skeleton recovered, hopefully there is enough for positive identification. In either case, it looks like this will make it to publication as first recorded fossil Amiid from Maryland and the Miocene east coast (not including Florida ). I will keep you updated as this comes about. Many thanks to you and to Jeff C. for helping out with obtaining the modern bowfin material, it has helped us in putting some of the pieces of the past back together.
William C
Paleontology Department
Calvert Marine Museum

On Jun 16 2004 the Group received this request:

Hello, my name is William C. I work for the Paleontology Dept. at the Calvert Marine Museum in Calvert county Maryland.
Recently , I dicovered a partial fossil Amiid skeleton consisting of about 70% of the head and one centra. This fish was found in brackish to marine sediments that date to about 10 - 15 million years, Miocene epoch, Saint Marys formation. As far as I know this is the only Miocene Amiid known from the east coast. The only way for us to tell whether or not this specimen is the same as the modern species would be to compare it to a number of modern specimens. Unfortunately, our comparative osteology dept. is weak. Because bowfins are not found in our area it is difficult for us to obtain such specimens. I am looking for someone who would be willing to donate about 12 whole, frozen bowfins for study. Animals ranging from about the 10 to 24 inch range would be required to look at morphologic changes through chronologic age. Being a non-profit institution, our funds are very limited but we would be able to cover the cost of shipping. If you know of someone who is willing to help, it would be greatly appreciated.

On Jun 28 and 29, Jeff C did a great job for BAG. He took the time to fulfill Bill's request. The fishing, as always, was the fun part. Scrounging up coolers and dry ice, prepping and wrapping the fish, and getting it all FedEx'd overnite was a chore. BAG donated the funds for shipping. We thank you Jeff and William for helping to promote understanding of our favorite sportfish. Check back for updates on William's research.

Deformed fin still thrives

Kyle F caught this fin in Upstate NY. The lower jaw is only half-formed but the fin was healthy. Says a lot for their predatory skills. 07/28/04

Troy (VT02) summarizes bowfin spawning info

I have researched Amia calva just like we discussed before. I went to and found some valuable info. The information below is in my own words as to not to copy their exact work. But you can have my work, it's for BAG research.

Main Ref:4639
Bowfin Eggs info,

Freshly layed eggs are colored a yellow,amber or orange. Eggs are sticky and stick to dead and upright vegetation or rocks. As the eggs get older they will darken or be different in colors with the location. Some may be white to yellowish brown, charcoal gray to dark grayish brown.

Main Ref:Balon,E.k.,1990
Bowfin Reproduction,

Bowfin spawn at 6-19 degrees Celsius (43-66 F), with the optimum at 61-66 F. They spawn in colonies in protected locations such as in weeds, tree roots and even under logs.

Main Ref:Page, L.M. and B.M. Burr.1991.(Ref.5723)

They rely on scent as well as their sight to find food. They capture their food by gulping water. When the young leave the nest they are in a tight group and guarded by the male.
Troy H 05/03/04

Shiners and Fins

Troy H found this article about Golden Shiners utilizing active bowfin nests for spawning. I find it interesting that the shiners don't become a light snack:

DavidG finds a fry cloud

I tried my luck with the bowfin today. B@$$ were bedding around practically every stump I came across. Unlike last time I saw just one gar the whole time I was out there. I had a few bowfin cruise by me, but never managed anything more than the taunting stare they were giving me. Anyway as I practiced my sight fishing skills in the shallows I suddenly fixed on a massive black cloud in the water. I thought for sure it was bullheads; it looked completely identical to a school of bullheads. As I paddled all the way up to them I noticed somthing large swam away from them, then I noticed these bullheads didn't have whiskers! I looked harder at the tiny black tadpole-like figures in the massive cloud. I was noticing individual ones coming up and gulping the surface - that gave it away. I scooped up handfuls, millions of tiny bowfin fry. I didn't manage to get great pics, but I got a few. I kept a couple for an aquarium, As I was leaving, I saw the male slowly swimming around my boat but I wasn't about to try to catch him. I just let him go about his way guiding the tiny bowfin along.
David G 04/07/04

Bowfin Stomach Contents Survey -- What do bowfin eat?

From Fisheries Grad Student Andrew P:
TITLE (ENGLISH): Food Habits of Bowfin in the Black and Lumber Rivers, North Carolina
AUTHOR(S): Ashley,-K.W.; Rachels,-R.T.
CONFERENCE INFORMATION: 53. Conference of the Southeastern Association of Fish and Wildlife Agencies, Greensboro, NC (USA), 6-10 Nov 1999
Eversole,-A.G.; Wong,-K.C.; Doerr,-P.; Woodward,-D.; Mazik,-P.;
Lequire,-R.-(eds.) 7221-Covey-Trace-Tallahassee-FL-32308-USA
Southeastern-Association-of-Fish-and-Wildlife-Agencies 1999 pp. 50-60.
ABSTRACT: We examined food habits of bowfin (Amia calva), in the Black and Lumber rivers, North Carolina. Stomachs from 192 Black River bowfin and 175 Lumber River bowfin were analyzed to determine frequency of occurrence and percent by number and weight of individual food items consumed from 1994 to 1997. Crustaceans [primarily crayfish (Astacidae) and grass shrimp (Palaemonidae)] were the dominant food item consumed by bowfin in both rivers. They occurred, on average, in 79% of Black River bowfin stomachs containing food and accounted for 65% by number and 53% by weight of all food items consumed. In the Lumber River crayfish occurred, on average, in 71% of bowfin stomachs containing food and accounted for 63% by number and 27% by weight of all food items consumed. Fishes, primarily centrarchids and ictalurids, were of secondary importance in the diet of bowfin. Other fish of minor importance included American eel (Anguilla rostrata), bowfin, creek chubsucker (Erimyzon oblongus), and pirate perch (Aphredoderus sayanus).

Scientific Articles on Amia calva

Bowfin are unique fish, and unfortunately are not often studied. Our Science Advisor, Professor Hedrick, studied bowfin during his graduate program; two of his papers are linked and summarized below. This page will be dedicated to scientific data and research into our beloved bowfin. The articles may have a lot of technical jargon, but if getting smarter was easy.... For the non-scientists among us (myself included), I suggest that you be patient, use a dictionary, and you'll get the gist of it. Superscripts and subscripts don't display well here, so jump to the original link for better readability as well as greater detail.

The effects of altered aquatic and aerial respitory gas concentrations on air-breathing patterns in a primitive fish (Amia calva)
Michael S. Hendrick* and David R. Jones

The mechanisms and physiological control of air-breathing were investigated in an extant halecomorph fish, the bowfin (Amia calva). Air flow during aerial ventilation was recorded by pneumotachography in undisturbed Amia calva at 20-24°C while aquatic and aerial gas concentrations were independently varied. Separation of aquatic and aerial gases was used in an attempt to determine whether Amia calva monitor and respond to changes in the external medium per se or to changes in dissolved gases within the body. Air flow measurements revealed two different types of ventilatory patterns: type I airbreaths were characterized by exhalation followed by inhalation; type II air-breaths, which have not been described previously in Amia calva, consisted of single inhalations with no expiratory phase. Expired volume (Vexp) for type I breaths ranged from 11.6±1.1 to 26.7±2.9mlkg^-1 (95% confidence interval; N=6) under normoxic conditions and was unaffected by changes in aquatic or aerial gases. Gas bladder volume (VB), determined in vitro, was 80mlkg^-1; the percentage of gas exchanged for type I breaths ranged from 14 to 33% of VB in normoxia. Fish exposed to aquatic and aerial normoxia (PO2=19-21kPa), or aerial hypercapnia (PCO2=4.9kPa) in normoxic water, used both breath types with equal frequency. Aquatic or aerial hypoxia (PO2=6-7kPa) significantly increased air-breathing frequency in four of eight fish and the ventilatory pattern changed to predominantly type I air-breaths (75-92% of total breaths). When fish were exposed to 100% O2 in the aerial phase while aquatic normoxia or hypoxia was maintained, air-breathing frequency either increased or did not change. Compared with normoxic controls, however, type II breaths were used almost exclusively (more than 98% of total breaths). Type I breaths appear to be under feedback control from O2- s e n s i t i v e chemoreceptors since they were stimulated by aquatic or aerial hypoxia and were nearly abolished by aerial hyperoxia. These results also indicate that Amia calva respond to changes in intravascular PO·; however, externally facing chemoreceptors that stimulate air-breathing in aquatic hypoxia cannot be discounted. Type II airbreaths, which occurred in aerial hyperoxia, despite aquatic hypoxia, appear to be stimulated by reductions of VB, suggesting that type II breaths are controlled by volume-sensitive gas bladder stretch receptors. Type II breaths are likely to have a buoyancy-regulating function.

Key words: air-breathing fish, bowfin, Amia calva, hypoxia, type I breath, type II breath, expiratory volume, buoyancy.

Control of gill ventilation and air-breathing in the bowfin Amia calva
Michael S. Hendrick,* and David R. Jones

The purpose of this study was to investigate the roles of branchial and gas bladder reflex pathways in the control of gill ventilation and air-breathing in the bowfin Amia calva. We have previously determined that bowfin use two distinct air-breathing mechanisms to ventilate the gas bladder: type I air breaths are characterized by exhalation followed by inhalation, are stimulated by aquatic or aerial hypoxia and appear to regulate O2 gas exchange; type II air breaths are characterized by inhalation alone and possibly regulate gas bladder volume and buoyancy. In the present study, we test the hypotheses (1) that gill ventilation and type I air breaths are controlled by O2-sensitive chemoreceptors located in the branchial region, and (2) that type II air breaths are controlled by gas bladder mechanosensitive stretch receptors. Hypothesis 1 was tested by examining the effects of partial or complete branchial denervation of cranial nerves IX and X to the gill arches on gill ventilation frequency (fG) and the proportion of type I air breaths during normoxia and hypoxia; hypothesis II was tested by gas bladder inflation and deflation. Following complete bilateral branchial denervation, fG did not differ from that of sham-operated control fish; in addition, fG was not significantly affected by aquatic hypoxia in sham-operated or denervated fish. In sham-operated fish, aquatic hypoxia significantly increased overall air-breathing frequency (fAB) and the percentage of type I breaths. In fish with complete IXX branchial denervation, fAB was also significantly increased during aquatic hypoxia, but there were equal percentages of type I and type II air breaths. Branchial denervation did not affect the frequency of type I air breaths during aquatic hypoxia. Gas bladder deflation via an indwelling catheter resulted in type II breaths almost exclusively; furthermore, fAB was significantly correlated with the volume removed from the gas bladder, suggesting a volume-regulating function for type II air breaths. These results indicate that chronic (34 weeks) branchial denervation does not significantly affect fG or type I air-breathing responses to aquatic hypoxia. Because type I air-breathing responses to aquatic hypoxia persist after IXX cranial nerve denervation, O2-sensitive chemoreceptors that regulate airbreathing may be carried in other afferent pathways, such as the pseudobranch. Gas bladder deflation reflexly stimulates type II breaths, suggesting that gas bladder volume-sensitive stretch receptors control this particular air-breathing mechanism. It is likely that type II air breaths function to regulate buoyancy when gas bladder volume declines during the inter-breath interval.

Key words: hypoxia, air-breathing, gill ventilation, gas bladder, buoyancy, stretch receptor, bowfin, Amia calva.

Also of interest is this link. L.oculatus is our friend from the other side, the spotted gar:

Air-breathing during activity in the fishes Amia calva and Lepisosteus Oculatus
C. G. Farmer and D. C. Jackson

This study is interesting because it verifies what many of us have witnessed: Bowfin gulp air even in oxygen-rich water. The study reveals that both the bowfin and spotted gar get more than 50% of their oxygen from breathing during moderate exercise in oxygen-rich water. Of course, the "why" is still unknown, but this duplicates what Troy H and others have observed; bowfin gulping air in fast, oxygenated waters of a spillway.

An examination of central chemosensitivity in an air-breathing fish (Amia calva)
By M. S. Hendrick, M. L. Burleson, D.R. Jones, and W. K. Milsom

J. exp. Biol. 155, 165-174 (1991)
The role of central chemosensitivity in the control of ventilation in fishes was investigated directly by perfusing a mock extradural fluid (EDF) through the cranial space in the medullary region of conscious air-breathing fish, Amia calva. Perfusions with Sudan Black dye showed that the mock EDF communicated with the cerebrospinal fluid (CSF) and entered the cerebral ventricles. Altering the PO2, PCO2, and/or pH of the mock EDF had no effect on gill- or air-breathing rates, heart rate or blood pressure during exposure to normoxic water. Aquatic hypoxia, however, stimulated gill ventilation and elevated blood pressure, but did not affect heart rate; altering the gas tensions and/or pH of mock EDF still had no effect on recorded variables. Sodium cyanide (NaCN) added to the mock EDF caused struggling at concentrations above 500 µg/ml, but did not uniformly stimulate ventilation. These results suggest that central chemoreceptors, which mediate cardiovascular or ventilatory reflexes, are absent in Amia.

This paper is not posted at jeb.biologists; I do have a complete hard copy direct from the author. E-mail me if you would like additional information on this paper

Periodic air-breathing behavior in a primitive fish revealed by spectral analysis
Michael S. Hendrick, Stephen L. Katz and David R. Jones

This short communication shows that Type I air-breaths in bowfin do occur at regular time intervals, and that in hypoxic conditions (low PO2) the interval is approximately half that found in normoxic conditions. The times indicated in the study are 30 mins for normoxic and 15 mins for hypoxic conditions. Does this mean if we aren't seeing them rise, they aren't there? Hmmm.

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