What is a Bowfin?
The bowfin is an aggressive, predator fish found throughout the eastern USA into southern Canada. Its scientific name is Amia calva. It has other common names including:choupique, grindle, grinnel, cypress trout, mudfish, etc.
The bowfin is considered to be a primitive fish. Its air bladder is modified as a “lung” and it can survive in water with virtually no oxygen in it. The bowfin is classified by most people as a trash fish eaten only by ethnic groups that usually use the flesh to make fish cakes.
Why Culture Bowfin?
In recent years, bowfin eggs (roe) has proven to be an excellent substitute for paddle fish (spoonbill catfish) roe in production of excellent quality domestic caviar. This so-called”Cajun Caviar” has generated much interest in aquaculture circles about the feasibility of growing bowfin for caviar production.
USL and Bowfin
The USL Crawfish Research Center has been conducting very limited research in bowfin culture since 1989. Jay Hurter, the Director, had conducted some earlier studies on bowfin and tilapia polyculture in the 1970s while he was affiliated with Southern University in Baton Rouge, Louisiana. This work was one at the LSU Aquaculture Center in Baton Rouge in cooperation with LSU personnel. Dr. Hurter also observed young of the year bowfin growth in reservoir tanks of a recirculating aquaculture system at the LSU Department of Civil Engineering CEASL Lab in the late 1980s.
This report summarizes the results of the USL and Southern University/LSU bowfin aquaculture research, The research has never been directly funded and has had to be done piecemeal for that reason. Many questions are unanswered but new data are presented that should be of benefit to anyone interested in pursuing bowfin culture.
Some Thoughts About Bowfin Culture Spawning
Bowfin have been successfully spawned in open ponds at national fish hatcheries at least twice. In each case, the adult fish, over 2 pounds each, were stocked into ponds with vegetation on at least part of the bottom. This seems to be essential as bowfin males which make the nest and guard the eggs and the young bowfin incorporate some vegetation into the nest.
At USL, we have stocked bare mud bottom 0.3 acre ponds with mature bowfin twice and have had mature bowfin in two mud bottom canals for two spawning seasons. We observed no spawning and found no young. We also stocked mature bowfin in ponds with vegetation one season. At least one possible nest was observed there; however, no young bowfin were ever recovered.
We have observed successful bowfin spawning twice at USL, spring 1990 and spring 1993. This occurred in a 20 acre wooded slough. This unit typically dries to no more than a quarter acre of narrow ditches of pools in a dry summer. No more than a dozen 34 lb bowfin were stocked in January and February of each year where young bowfin were recovered. The system dried completely in the summers of 1990 and 1991.
Bowfin are said to be able to “estivate” in mud if their habitat dries up. However, we have observed no survival of young of the year or brood bowfin when the referenced slough dried up completely. The soil, itself, is a loam rather than a heavy clay. Therefore, the loss of the fish may be because the loam soil did not retain moisture as a clay soil would.
Why did the bowfin spawn successfully in the slough and not elsewhere? This likely has several explanations. (1) The fish may not have had adequate food in the small, 0.3 acre ponds where we had held as many as 25, 34 lb fish. We did apply catfish feed and, on occasion put cut menhaden (pogie) or shad in the ponds.
There was also some crawfish available as forage. In addition, the fish did appear to be healthy. Finally, the fish were stocked in the slough in January of each year and hardly had enough time to feed very much at a time when water temperatures were in the 50-60° F range before spawning.
(2) There was no vegetation to speak of available in the 0.3 acre ponds but it was available in the canals and the slough. If vegetation is required for successful nesting, then this could explain why the bowfin did not nest successfully in the 0.3 acre ponds. Note that bowfin eggs are adhesive. The newly hatched larvae also have “adhesive” glands. Vegetation would provide a substrate on which eggs and newly hatched larvae could attach, keeping them out of bottom sediments that might suffocate them.
(3) Bowfin spawn in flooded swamps and marshes in the spring. This could have two influences on our observations at USL. First, the fish in the slough were subjected to a “normal” increase in water from January-February rains. Water levels were fairly static in the other ponds. Second, bowfin eggs and young bowfin are readily eaten by predators, especially fish like green sunfish and bullhead catfish.
They are at risk in the nest and again while they are in their characteristic schools, protected by their fathers. Spawning areas are generally characterized by the absence of such fish predators because of the dilution effects on fish populations through the flooding of large acreages of marginal wetlands. The canals and vegetated ponds used in our studies had dense populations of green sunfish and, in the case of the canals, many bullheads. So, if one wants to spawn bowfin, it seems clear that he/she should stock healthy broodfish into a small pond kept dry for several months to permit growth of some vegetation and to eliminate all potentially predaceous fish.
While crawfish could clearly eat the eggs, bowfin spawn in seasonally flooded wetlands characterized by high levels of crawfish production. Stocking rates should be similar to those used for largemouth bass – 5 to 10 pair per acre if the parents are left with the fry or 40-50 pair per acre if the young are to be removed.
This recommendation is based on the similarities in spawning behavior of the two species. Remember, male bowfin have a very distinct black spot just in front of the tail (on the caudal peduncle) while females do not. Egg laden female bowfin will have swollen abdomens.
(The best source of information about bowfin spawning is a short report written by Mr. Anthony Mayeux at the National Fish Hatchery in Natchitoches, Louisiana.)
Bowfin are carnivorous fishes. The tiny young bowfin consume just about anything that wiggles and can tear apart prey too large to swallow whole using very formidable teeth and strong jaws. The young fish swim in schools guarded by their respective fathers until they reach 3-4 inches in length. There may be several thousand in such a school which is bucket size when they leave the nest but can occupy an area several feet in diameter by the time they part company 4-6 weeks later.
These schools of fish consume anything edible in their paths feeding first on small zooplankton and benthic worms and insects. They quickly graduate to small crawfish, especially soft-shell crawfish, small fish, and larger insects. Juvenile and adult bowfin just move to larger prey.
Bowfin do not, however, have a feeding habit that does make their aquaculture a realistic consideration. That is, they do eat fresh, cut bait including beef liver and heart, shad, etc. and dead, but flesh or fresh frozen crawfish and shrimp. This means, then, that they can be fed manufactured feeds.
We have never been able to get bowfin to eat dry, pelleted feeds such as those used for catfish and trout culture. In tanks, the young fish will grab a pellet but spit it out immediately. In ponds, we have never seen bowfin eating pellets and growth and survival of young bowfin was very poor relative to that which would be realized by providing such feed to catfish and/or trout fingerlings.
We took the position that we could make a wet pellet that bowfin would eat. This was done by putting roughly 50% common carp fillet, 40% common carp viscera (guts) -mostly eggs– and 10% floating catfish fingerling feed (36% protein) into a food processor and grinding it until it became a “red goo.” Small bowfin, 2-3 inches long “loved” theft “grinnel goo!” This moist feed sticks to one’s fingers. The small bowfin would grab the feed and allow themselves to be pulled out of the water before letting go. We also secured a 60+% protein semi-moist fish pellet from Rangen Feeds. The pellets were really too small 1-3/25 inch for the small bowfin when it arrived but the fish would eat it if we made bigger pellets by squeezing the smaller ones together.
We found that 2-3 inch bowfin would readily eat small chunks of beef liver over a 3-4 day period but then stopped eating it. We had a fairly high mortality after they stopped eating the liver and concluded that there was a nutritional deficiency involved. The survivors readily ate cut fish, our wet pellet, and soft-shell crawfish once we stopped using the liver.
We really do not have good experience feeding bowfin in ponds with any sort of dry manufactured pellet. It seems reasonably certain, however, that some form of wet pellet would be readily accepted. This would involve using a standard wet pellet recipe where whole fish such as shad or menhaden were passed through a meat grinder with a small amount of flour for binding purposes and, perhaps, a vitamin/mineral premix.How
Much to Feed Bowfin?
It takes roughly 4-5 pounds of fish flesh or ground wet feeds to produce one pound of carnivorous fish. While trout and catfish pellets generate feed conversion values of 1-2 pounds of feed per one pound of gain, these are dry feeds with 5-10% moisture while “wet” feeds have 70-80% moisture in them. Food consumption is highly correlated with water temperature because fish are “cold-blooded”.
These factors apply to bowfin as well. Furthermore, once a fish is mature, it diverts more of the nutrients in its food to producing eggs and sperms than to increasing its overall size. As a result, food conversion efficiencies decline, often very dramatically.
Someone trying to grow bowfin will probably feed the fish 5-7 pounds of ground fish or wet feed in its first year, recognizing that the fish will consume more food in the warm months of May, June, July, August, and September and progressively less food in the October-March period. Thus, the prospective bowfin farmer would have to divide his bowfin ration amongst the warm months and reduce it for the cool months. Use of feeding stations would probably be advisable to try to determine how much the fish are eating.
However, remember, fish will often gorge themselves just like people. As a result, food conversion values are reduced because digestion efficiency decreases. Thus, care must be taken to avoid “overfeeding.”
How Fast Do Bowfin Grow in South Louisiana?
We have experience in growing bowfin in ponds and in recirculating tank systems. Bowfin normally spawn in late January-February-early March in south Louisiana depending on water conditions, especially “spring” flooding and temperature – low to mid 60_ F. The young fish reach a size of 3-4 inches by early-late April when their “natal” schools break up.
Our experience has shown that the solitary bowfin reach 6-7 inches by early June in ponds. When conditions are favorable – low densities and plenty of food – they grow to 16-20 inches, around 1.5 lbs, by early December when growth more or less stops until the waters warm in the spring. We have observed this level of growth at densities of 30-60 fingerlings per acre in ponds full of prey items like tilapia, mosquitofish, grass shrimp, and crawfish. Maximum depth was 3-4 feet in the small ponds, about 0.1 acre. However, fish in 12-18 inch deep ponds grew to only 10-12 inches in the same period.
The main questions that a potential fish farmer asks, at this point, would be (1) are they mature and (2) will they produce eggs at these sizes? The farmer asks these questions because the principal bowfin product is the eggs for caviar. The answers are a bit complicated.
Published data show that a 1.5 pound female bowfin is mature. Such males would be mature but they do have the potential to be mature at smaller sizes. We have 10-11 inch male fish, 10 months old about 0.5 lb that have developed spawning colors – vivid green highlights along the ventral side (bottom) plus intensification of the color of the black tail spot.
We have not killed the 10 month old, 0.5+ lb males and 1.5+ lb female bowfin to examine their reproductive organs. We have not made any efforts to spawn them, either. Our gut feeling is that the males probably can spawn but that the females would likely have to be two years old to spawn on a predictable basis. Furthermore, even if the 1.5+ lb females could spawn, they would not produce as much roe as a 3 or 4 lb fish.
Note, reproduction of bowfin in one year is not really an unreasonable speculation when one realizes that largemouth bass and crappies with very similar feeding habits mature and spawn in one year in the region.
It may appear that bowfin grow very rapidly in southern Louisiana. But, one must consider that it is rare to find bowfin much smaller than a pound. While the adult fish is a vicious carnivore, the young of the year fish are potential prey for all manner of predatory fishes. Therefore, they must grow very quickly or be eaten by other predatory fishes. Once they are too big to be swallowed, they are relatively safe.
Survival and Mass Culture
High density culture is desirable if bowfin aquaculture is going to be successful on a major scale. This can only be accomplished if the small fish will eat a convenient feed such as wet pellets and survive at high densities. Bowfin become solitary once they reach “fingerling” size. We put several thousand 2-3 inch bowfin fingerlings into a 0.3 acre pond in March of one year, fed daily with a floating 36% protein fingerling catfish chow, and recovered approximately 50, six-inch fish at the end of June. It is clear that the fish did not eat the pellets. We simply do not know what would have happened to them if we had used a wet pellet.
The referenced fish were put into a 1.5 acre pond with several thousand catfish. The catfish were fed daily and the pond had large numbers of mosquitofish and grass shrimp in it. All fish were removed in November and December. Most of the bowfin survived but grew to only 10-12 inches. This suggested that they were food limited based on the results of our earlier pond studies at similar densities.
In April 1993, we put 50, two-inch bowfin young of the year into a 3′ x 7′ x 12″ deep (3″ of water later raised to 6″ of water) rectangular fiberglass trough in a recirculating aquaculture system. After roughly a month, the fish were 4-5 inches and began establishing territories. By mid-December, only four fish remained in the tank. At least 15-20 died during the growing period because their brothers and sisters “beat them to death.” Cannibalism seems to have accounted for at least 10 deaths. The four survivors we Do these results mean that high density bowfin culture is not “feasible?” In our opinion, the answer is no.
The results mean, first of all, that square, shallow cultural containers are not suitable for growing young bowfin – they fight for comers. Thus, round containers should give better results than square containers. We observed that half a dozen young of the year bowfin grew to about 18 inches in a year in round tanks – 3′ x 3′ at the LSU Civil Engineering CEASL Lab.
Second, we simply do not know what an appropriate density is for bowfin in ponds or intensive culture systems. Good growth of channel catfish fingerlings is observed at densities around 2,000 per acre. This might be a target density of pond culture of bowfin if they respond well to wet feeds.
Most fishes grown in cages and tanks have an optimal density where territorial behavior breaks down and the fish stop fighting each other. While it does not appear that catfish would be dangerous to each other as bowfin with their tooth-filled jaws, catfish have many tiny teeth arrayed in “abrasive” pads with which they can tear each other gradually apart. Catfish fingerlings are stocked into cages for grow out at densities around 200 per cubic yard. This, then, might be a target density to try for intensive bowfin culture.
Third, high density culture invariably requires periodic size grading to prevent size disparity leading to cannibalism. This is much easier to accomplish in intensive culture systems than in ponds.
Fourth, it is not clear what appropriate feeding schedules should be used for cultivating bowfin. However, it is apparent that they should be fed several times each day in tanks and, most likely, in ponds.
Remember, bowfin breath air. They must have access to the surface to gulp air or they will drown. It is likely that bowfin can be grown at much higher densities than most other fish because they can breath air. A similar situation exists with the so-called walking catfishes, genus Clarias, that can be cultivated in systems with very little oxygen and at very high densities.
The reader will note that there just isn’t much information about bowfin culture and life cycles presented in the scientific literature. There is one group, however, that is working on bowfin life cycles in Louisiana. That agency is the Louisiana Department of Wildlife and Fisheries. The data from the LDWF study should be useful to persons interested in trying to culture bowfin. Those interested in the LDWF project should contact Messrs. Bennie Fontenot and Arthur Williams – Freshwater Fisheries Division, Louisiana Department of Wildlife and Fisheries, P.O. Box 98000, Baton Rouge, Louisiana 70898.
So, can bowfin become a successful aquaculture species in Louisiana and elsewhere? We are optimistic that this is possible based on the data that we have generated up to now. However, properly funded research – private and/or public -will be necessary before a final conclusion can be made.