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NFC: Bowfins
Bowfin Culture At The University Of Southwestern Louisiana
By Jay V. Huner
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.)
Feeding Bowfin
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.
Conclusions
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.
Robert Rice
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