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Appendix B
Freshwater Aquaculture
in the United States
OVERVIEW OF PRODUCTION
Of the roughly 0.3 million metric tons (mmt) of aquatic life grown for
food in the United States, three-quarters or more are freshwater organisms.
Most of the freshwater production consists of catfish, crayfish, and rainbow
trout, in that order of importance. Large numbers of freshwater organisms
are grown for purposes other than their immediate use for food. These
include ornamental fish, baitfish, trout and other species stocked for recre-
ational fishing, and salmon small released at sea for ocean ranching opera-
tions. In these latter applications, the fish are not normally sold, utilized,
or accounted for by weight, so that it is difficult to assess their importance
in U.S. aquaculture relative to the importance of the food species.
Catfish
Catfish farming is, far and away, the major aquaculture success story in
the United States. Beginning no earlier than the mid-1960s, when a few
thousand kilograms of channel catfish (Ictalurus punctatus) were grown in
Arkansas, the annual crop had increased to more than 1,000 metric tons
raised in 18 different states by 1969. By 1980, the center for the industry
had shifted to the lower Mississippi delta, and national production had in-
creased to more than 20,000 metric tons. Since then, catfish farming has
grown by some 30 percent per year to a crop of 155,000 metric tons sold to
processors in 1989, 90 percent of which is grown in the state of Mississippi
(Rhodes, 1987~.
232
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FRESHWATER AQUACULTURE IN THE UNITED STATES
233
Availability of fingerlings early in the year remains a major constraint
to the industry. Only recently have efforts been made in the area of demand
spawning through manipulation of photoperiod, temperature, and diet. Some
stock improvement through selective breeding also has been initiated, to-
gether with modern genetic manipulation, such as gynogenesis, to produce
faster-growing all male populations. A chronic problem in catfish culture is
off-flavor, which may result in the rejection of entire crops.
The industry currently tests fish before harvesting and processing to
ensure that off-flavor fish are eliminated before marketing. With the in-
crease in production, the price of catfish dropped in 1989 from $1.72 to a
low of $1.39 per kilogram (kg) of whole fish at pond side, suggesting that
the market might be saturated. However, creation of a marketing association
in October 1989 resulted in a price rise back to $1.72 by March 1990 while
production continued to increase. At that price, the current annual crop has
a value to the grower of some $265 million (Hurter, 1990a, 1990b).
Crayfish
The inhabitants of Louisiana, many of whom are of French background,
have long harvested and enthusiastically consumed native populations of
crayfish (locally "crawfish"), a food virtually ignored by consumers in much
of the United States but highly popular in parts of Europe. Louisianians
have also, for many years, practiced a simple form of aquaculture for the
most popular and abundant species, the red swamp crayfish (Procambarus
clarkiiJ and, to a lesser extent, the white river crayfish (P. blandingiJ.
Crayfish culture is an extremely nonintensive, low-cost form of aquatic
farming that is barely distinguishable from capture fishing. Shallow (<1.0
meter [m] wetland ponds (often rice paddies) are stocked (usually just once)
with adult animals at 50 to 100 kg per hectare. They often are planted with
starter populations of several species of edible plants (if rice is not present
in abundance), such as alligator grass (Alternanthera phylloxeroides) and
water primrose (Jussiaea spp.J. However, the crayfish eat almost any soft
aquatic or terrestrial plant and often will thrive on natural vegetation.
After mating occurs in late spring, the ponds are slowly drained. The
animals then dig and move into burrows in the soft mud bottoms, where
they remain until egg laying occurs in early fall. At that time, the ponds are
refilled, the young hatch from the eggs, and growth proceeds until the next
mating season. Once ponds are initially stocked with crayfish and, if neces-
sary, planted with vegetation, the aquaculturist's role is merely to manipu-
late the water level of the pond.
Harvesting is by trapping, which is rather primitive and inefficient, and
represents the most costly aspect of the culture operation, but which may
be done throughout the flooded period (i.e., from November to May, with
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234
APPENDIX B
highest production from March to May). Traps are traditionally baited with
fish wastes. Artificial baits are now formulated by some of the large feed
manufacturers, but their use is economically marginal. Crayfish and rice
are often grown in rotation in the same pond, but care must be taken to
guard against the use of pesticides, to which the crustacea are highly sensi-
tive.
During the 1970s, about 1,000 metric tons of crayfish were reared on
7,000 hectares of ponds in Louisiana. Since then, the industry has ex-
panded rapidly in response to increased local and international demand, the
latter exacerbated by the decimation of European crayfish populations by
disease. By the mid-1980s, farms had spread into neighboring Texas, Mis-
sissippi, and Florida, and yields approached 50,000 metric tons from 40,000
hectares of ponds.
In danger of overproduction, the industry increased marketing efforts,
with the result that the more popular local "Cajun" and "Creole," as well as
the more traditional French, recipes are now offered by specialty restaurants
throughout the United States. However, continued expansion of the indus-
try (53,000 hectares of ponds in Louisiana alone in 1988-1989) eventually
led to market saturation and a drop in price to $0.77/kg by 1990, which has
led to a decrease in intensification of the farming (i.e., trapping) effort and
a corresponding decrease in yield per unit area, with an overall current yield
of approximately 30,000 metric tons by the industry and a value to the
grower of $24.5 million (Hurter, 1990a, b).
A new product within the past few years is newly molted soft-shelled
crayfish, comparable to soft-shelled crabs both in method of production and
in utilization (Hurter, l990c). Because of present marketing problems with
traditional crayfish crops, there was a rush by growers to the production of
soft-shelled crayfish in 1988-1989, which unfortunately quickly saturated
the new undeveloped market for that product. The future of the U.S. cray-
fish culture industry is therefore currently in a state of some uncertainty
(Catfish News, 19891.
TroutlSalmon
Trout culture is undoubtedly the oldest form of freshwater aquaculture in
the United States, having been introduced from Europe more than 100 years
ago to provide or enhance sport fishing in both private and public waters.
Today, more than 200 million trout of several species are reared in some
350 state and federal hatcheries for distribution to public waters for sport
fishing.
An additional 1 billion (approximately) Pacific salmon are reared to the
size of smolt (the physiological condition at which they may be introduced
to salt water, a stage that varies in size and age with the species of salmon)
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FRESHWATER AQUACULTURE IN THE UNITED STATES
235
in federal and nonprofit private hatcheries in the Pacific Northwest for
subsequent release to the sea. This program is carried out as mitigation for
the loss of natural spawning areas in rivers through dam construction or,
more recently, simply as enhancement of natural reproduction. Return of
stocked small as mature salmon generally averages 2-5 percent, a figure
that has increased with the production of larger, healthier smelt stock and
now accounts for a significant fraction (about 30 percent or more) of U.S.
salmon landings.
Such hatchery operations, particularly at the federal level, have provided
the principal basis for development of the technology of salmonid culture.
This has now become routine, and no striking new advances in the field
have been made recently, but there has been steady improvement of diet and
reproductive control, as well as some significant stock improvement through
selective breeding.
Trout and salmon normally inhabit cool, clean water, and their cultiva-
tion, therefore, depends on the rapid exchange of flowing temperate water
(10-20°C) of high quality. Eggs and sperm usually are stripped artificially,
and eggs are incubated and fry reared to fingerlings in flowing water sys-
tems within hatcheries. Fingerlings are then traditionally reared outdoors to
the desired size in concrete raceways, although other grow-out systems
have been used successfully. The fish accept artificial formulated feed as
soon as the yolk sac is absorbed, and appropriate formulations have been
developed for each stage of their growth and development.
Although several species of trout are hatchery reared for sport fishing,
the cultivation of trout for food has been restricted largely to the rainbow
trout (Salmo gairdneri now called Ancorynchus mykiss), native to the U.S.
Pacific Coast. Farming of the species for food was first begun in the l950s
in the state of Idaho, primarily owing to the advantage of a bountiful supply
of cold, clean running spring water issuing from the Rocky Mountains in
the Snake River valley. Although trout are now grown for food in virtually
every state with a suitable climate for their cultivation, 76 percent of the
U.S. production of some 25,000 metric tons still comes from Idaho.
The industry has grown slowly over the past decade, increasing by ap-
proximately 5 percent per year, on average. The principal constraint to
more rapid growth is the relatively low price of the product, currently about
$2.40/kg, which is set by competition from Japan and Europe but is mar-
ginal for a species that requires high-quality feed and relatively intensive
culture technology. Traditionally, the product has been a portion-size (340
grams, or 3/4 pound, 12 inches) fish, fresh or frozen, gutted, and head-on.
A trout of that size used to be grown in Idaho in about 18 months but now
takes just over a year from the egg. Increasingly, the fish are now marketed
fresh, and more than 50 percent are boned and sold as fillets. Further, an
increasing fraction is being grown to a larger size of 1 kg or more, is
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236
APPENDIX B
pigmented a vivid orange color, and is marketed fresh, presumably to com-
pete with marine cage-grown salmon and trout.
Bait and Ornamental Fish
Goldfish (Carassius auratus) were introduced to the United States from
Japan in the late nineteenth century and have been reared in this country for
nearly 100 years in a "goldfish belt" extending from Maryland to Arkansas.
Initially bred exclusively for the ornamental or aquarium trade, the smaller
and less attractive specimens began to be sold for bait and as feed for
carnivorous ornamental fish by the middle of this century. Today more
"feeder" than ornamental goldfish are reared and sold, but the value of the
latter is still greater (Martin, 1983~. At about the same time that goldfish
began to be used for bait, other more traditional bait, particularly the golden
shiner (Notemigonus crysoleucasJ and the fathead minnow (Pimephales notatusJ,
which belong to the same "minnow" family as goldfish, began to be reared
in the central part of the country, particularly Arkansas.
All of the above fish are reared in much the same way in shallow,
earthen ponds ranging in size from 0.1 to 25 hectares through which spring
water is circulated slowly. The fish spawn naturally along the pond banks
in the spring, either on grass or on artificial spawning mats made of sphag-
num moss or other fibrous material. In the latter case, the mats are usually
transferred to fishless breeder ponds after the adhesive eggs are laid, to
prevent cannibalism. Grow-out takes 6 to 18 months, depending on the size
of fish desired (Martin, 1983~.
The tropical ornamental fish industry is centered in Florida, which pro-
vides more than 90 percent of the aquarium fish, exclusive of goldfish, sold
in the United States. The industry consists of two kinds of operations: (1)
importation of exotic species from tropical Southeast Asia, Africa, or Latin
America for resale after holding and growing-out for various periods of
time; and (2) maturation, breeding, and rearing to marketable size of a
number of exotic species. Only about one-third of the sales by Florida
growers currently belong to the second category of fish grown throughout
their life cycle on the farms, and these represent 10 percent or less of the
total number of species handled. There are about 12 species groups in that
category, of which 5 (the live-bearing species) make up 70 percent of all
sales. However, an increasing number of the more difficult to rear egg-
bearing exotics have been brought under reproductive control by some pro-
gressive farmers in the past decade.
The fish are grown, for the most part, in small earthen ponds averaging
about 200 m2 in area, usually below the water table, so that they must be
pumped dry for cleaning and water exchange. In hot weather, they may
require aeration and, in cold weather, continuous pumping of deep, rela-
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FRESHWATER AQUACULTURE IN THE UNITED STATES
237
lively warm well water and/or covering of the surface. The fish are fed
prepared rations that differ considerably in formulation and amount applied.
Antibiotics, drugs, and chemicals are used as needed for disease, pest, and
weed control, but practices tend to be empirical and are far from standard-
ized in the industry.
A study by the Florida Game and Freshwater Fish Commission estimated
that the state's tropical fish industry consisted of some 215 full-time fish
farmers utilizing an area of 433 hectares with an annual value to the grow-
ers of $26 million in sales (Knox and Drda, 1982-1983~. Initially, the bait
and goldfish industries were similarly fragmented into small family units
but, over the past 25 years, have gradually become consolidated into fewer
larger farms. About 10 growers dominated the fancy goldfish industry in
the 1960s, and one large company has since captured about 80 percent of
the business. The larger feeder goldfish and bait minnow industry is repre-
sented by some 50 growers, of which one-half dozen dominate.
Documentation of the size and monetary value of these nonfood fish
culture industries in the United States is not well documented. One esti-
mate put "baitfish" production at 12,200 metric tons worth $56 million in
1987, but it is not clear what the category included. An experienced academ-
ic and commercial goldfish culturist estimated that industry to be worth
$10 million to $20 million to the farmer (Martin, 1983~. It would thus
appear that the entire category of nonfood fish culture has an annual value
to the grower of $50 million to $100 million, making it one of the economi-
cally more important forms of U.S. aquaculture.
Alligators
Alligators are valuable for their hides, worth up to $50 per linear foot on
the international market, and for their meat ($15/kg on the specialty food
market). A 4- to 5-foot animal can be grown from an egg in about 14
months and brings about $20 to $30 per foot (in late 1990~; wild animals
are more valuable and are priced at $40 to $50 per foot..
There are presently some 180 alligator farms, of which 90 are in Louisi-
ana and 40 are in Florida. Eggs are captured from wild nesting animals
under a carefully controlled licensing arrangement, which includes the pro-
viso that 17 percent of the reared stock be returned to the wild when they
reach 4 feet in length. The animals are grown in heated incubators and fed
rations prepared on-site from nutria, large swamp-dwelling rodents. Com-
mercially produced pelleted feeds are also available in several sizes. A 5-
foot alligator costs $50 to $75 to raise. Currently, about 100,000 cultured
alligators are marketed per year, making this fledgling industry worth
some $15 million to $20 million (Fish Farming International, 1990~.
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23g
Hybrid Striped Bass
APPENDIX B
Hybrids of the anadromous striped bass (Morone saxatilis) female and
the freshwater white bass (M. chrysops' male have been hatchery reared
since the 1960s for sport fishing and forage fish control in large southern
U.S. lakes and reservoirs. For the past decade, research has been carried
out on the feasibility of growing the hybrid as an aquaculture food crop.
These research and development efforts have included semi-intensive
pond culture in North and South Carolina and elsewhere along the eastern
seaboard, and highly intensive tank culture in the California desert using
. .. a. . . . ~
geothermal well water. the hybrid can be grown in either salt or highly
alkaline fresh water, the latter having most frequently been used in the
initial efforts. Several of these efforts have now achieved commercial sta-
tus, including a new intensive tank culture project in Mississippi. However,
the industry is still quite small.
, ~ ~ . ,
In 1987, approximately 450 tons were
marketed, of which 75 percent were produced by one of the intensive tank
farms in California.
The industry is still dependent on the female striped bass hybrid and the
male freshwater white bass hybrid, but it has not been able routinely to
produce sexually mature hybrids that spawn in captivity, relying instead on
hormonally induced spawning of ripe-running wild females. The latter are
difficult to acquire, both legally and logistically, and the supply of young
is restricted to one brief period of the year.
The intensive culture method, involving heavy application of high-pro-
tein feed, pumping large volumes of water, the use of liquid oxygen, and a
high capital investment for tanks and equipment, imposes a break-even
cost of $4 to $5/kg for the product to the grower. If wild stocks of striped
bass return to the East Coast in abundance, as appears now to be the case,
the cost of rearing the hybrid striped bass in captivity must be lowered
significantly, perhaps by the use of less intensive pond culture technology,
for the industry to prove viable (Van 01st and Carlberg, 1990~.
T., .
apla
Several species of the genus Tilapia (oreochromis), native to the lakes of
Africa, have now spread to tropical and semitropical habitats throughout the
world, including the southern United States. Herbivorous or omnivorous in
its feeding habits, Tilapia can be grown inexpensively in extremely dense
culture and with high yields. Not surprisingly, it has become a major target
for aquaculture throughout the tropical world.
A major constraint to tilapia culture is its early sexual maturation and
extreme fecundity, resulting in rapid overpopulation and stunting in ponds
and impoundments where it is stocked. The problem has recently been par-
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FRESHWATER AQUACULTURE IN THE UNITED STATES
239
tially resolved by hybridization of tilapia species to produce sterile or
monosex (all-male) offspring. Selective breeding of the hybrids has also
resulted in red varieties that are more attractive and marketable than the
dark-colored native species. It is now possible to produce red hybrid tilapia
of 0.5 to 1.5 kg in extremely dense, highly intensive tank culture. However,
to find market acceptance of the species in this country has proved difficult
at a price that is economically viable, and unlike its success elsewhere in
the world, tilapia farming in the United States has yet to become an estab-
lished industry.
Macrobrachium
The large freshwater shrimp or prawn, Macrobrachium rosenberghii, is
grown in small commercial operations in Puerto Rico and Hawaii. With the
exception of certain behavioral characteristics, such as dominance and
territorialism in large males (which can be at least partially alleviated by
frequent selective harvesting), there are no particular problems or constraints
to its cultivation. However, the young must be reared in salt water prior to
transfer to fresh water for adult grow-out, a factor that limits the places
where it can be reared. In addition, the animal is truly tropical in its habitat
requirement, so that year-round growth in most of the United States is
limited. A number of Macrobrachium farms were started up in Hawaii over
the past decade, but most have since gone out of business or have converted
to marine (penaeid) shrimp. Marketing problems have hindered commercial
success with the species.
Sturgeon
The white sturgeon iAcipenser transmontanus) is another anadromous
fish that grows equally well in salt water or hard fresh water. It has been
cultured primarily in California, where the industry has expanded rapidly
over the past five years, and the product has been marketed routinely at
attractive prices. To date, the culture system of choice is intensive tank
systems using large cylindrical fiberglass tanks supplied with flow-through
or recirculated fresh water. Pond culture systems have not been particularly
satisfactory for sturgeon.
Major problems encountered by the industry include disease and the reli-
ance on wild female brood stock. Diseases have been a recurring problem,
and identification of control measures is a priority research area, along with
development of domesticated brood stock. Mature males can now be pro-
duced routinely in captivity, and some cultured females (approximately six
to seven years old) have recently exhibited ovarian development. Maturation
of females in captivity could lead to an aquaculture-based caviar industry.
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240
APPENDIX B
Experimental culture of the Atlantic shortnose sturgeon (Acipenser
brevirostrum), an endangered species, has developed to the point that fin-
gerlings are produced regularly and are stocked in natural waters. Overall,
sturgeon culture is expected to continue to expand, but with most grow-out
operations located in freshwater, rather than saltwater, environments.
REFERENCES
Catfish News. 1989. Louisiana Florida slug it out on crawfish. (May/June):3.
Fish Farming International 1990. Alligator earnings boost U.S. farms. 17~5~: 21.
Huner, J.V. 1990a. Crawfish and catfish in Louisiana. Fish Farm. Int. 17~1~:28,
30.
Huner, J.V. l990b. Aquaculture worth over $200 million to Louisiana. Fish Farm.
Int. 17~4~:20.
Huner, J.V. l990c. New horizons for the crawfish industry. Aquaculture Magazine
16~5~:65-70.
Knox, R.H., and T.F. Drda. 1982-1983. Florida Aquaculture Survey, 1982-1983.
Florida Game and Freshwater Fish Commission on Aquaculture Project. 54 pp.
Martin,M. 1983. Goldfishfarming. AquacultureMagazine9~31:38-40;9(4~:38-
40; 9(51: 30-34.
Rhodes, R.J. 1987. Status of world aquaculture. Aquaculture Magazine 17th Ann.
Buyers Guide, p. 8.
Van 01st, J.C., and J.M. Carlberg. 1990. Commercial culture of hybrid striped
bass. Aquaculture Magazine 16~1~:49-S9.
Representative terms from entire chapter:
striped bass
