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SRAC Publication No. 163
April 1997 VI
PR
Revised
Cage Culture
Species Suitable for Cage Culture
Michael P. Masser*
Many species of fish are suitable ed on the number of pounds of Channel catfish are warmwater
for cage culture. Species which fish which can be reared per sur- fish. Optimum growing tempera-
have been researched and success- face acre of pond and per cubic ture for channel catfish is between
fully reared in cages in the south- foot of cage. A pond without aera- 80 and 85oF. Good growth occurs
eastern region of the U.S. include: tion can produce from 500 to 1,500 between 70 and 90oF. Above 95oF
catfish, trout, tilapia, striped pounds of fish per surface acre. fish feeding is reduced and
bass, red drum, bluegill sunfish, In a pond with aeration, 2,500 to deaths may occur. Below 70oF
crappie, and carp. Other species 4,000 pounds of fish per acre have feeding slows and, therefore,
may be suitable for cage culture been achieved. The maximum growth slows. Feeding essentially
but research has lagged behind pounds of production per cubic stops below 45oF.
other aquaculture research in foot of cage seldom exceed 14
recent years. Interest in cage cul- pounds in small cages and 11
ture has been revived as an alter- pounds in large cages (< 270 cubic
native crop for farmers outside feet). Commonly, cage production
traditional fish farming areas and will be between 5 and 8 pounds
in areas with topography not con- per cubic foot.
ducive to levee ponds. As this Cage production is possible in
interest continues to increase, ponds, lakes, reservoirs, strip pits,
more research into cage culture rivers and streams, and in cages
techniques and alternate species which range in size from 27 cubic
will no doubt occur. feet to several thousand cubic feet
A great deal of variability exists in (in large reservoirs). In this fact
the research and commercial liter- sheet, ponds will be the frame of Channel catfish
ature about suitable pond sizes, reference and only cages smaller
growing season, stocking densi- than 300 cubic feet will be consid- Channel catfish should be stocked
ties, and size of fingerlings to ered. only in a certain range of water
stock. Stocking rates or densities temperatures. Handling stress
are dependent on species, cage Catfish associated with stocking and qual-
volume and mesh size, pond sur- ity of fingerlings stocked are criti-
face area, availability of aeration, The channel catfish is the species
cal factors to be considered (see
and desired market size. In gener- most commonly cage cultured
SRAC Publication No. 164, Cage
al, stocking densities are calculat- today in the Southeast. Channel
Culture—Handling and Feeding
catfish have a well established
Caged Fish). Channel catfish can be
market and fingerlings are gener-
stocked into cages almost any
*Extension Fisheries Specialist, Alabama ally available. They tolerate many
time when the water temperature
Cooperative Extension System, Auburn extremes in water quality and
is above 50oF. However, stocking
University, AL. generally adapt to cages.
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at temperatures above 80oF may eries throughout the Southeast. Blue catfish, hybrid catfish (blue
adversely stress the fish and lead Not all of these strains do equally catfish male x channel catfish
to disease and possibly death. well in cages even though they female), and bullhead catfish have
Stocking poor quality fingerlings may grow well in open ponds. In been stocked in cages with limited
before the water reaches 60oF fact, strain research in cages sug- success. Blue and hybrid catfish
(when predictable feeding occurs) gest that some strains can grow as do not grow as well in cages as
can lead to handling stress com- much as 50 percent faster than channel catfish. Bullhead catfish
pounded by nutritional stress other strains. Therefore, probably have been raised in cages and
from the lack of food intake. For the best general advice is to talk to appear to do relatively well.
these reasons it is probably best to other cage producers in your area Recommended stocking size is a
stock when water temperatures and ask which fingerling source 6-inch fingerling. Bullheads do
are between 60 and 70oF. Of they like and have been successful not grow as large as channel cat-
course, fish farmers may have to with. Research done at Auburn fish, however, and are expected to
learn how to handle and stock University has shown that strains get to only 1/2 pound in a grow-
fingerlings at any range of tem- with a Kansas or Marion (named ing season. Bullhead fingerlings
peratures to be competitive and after the Federal hatcheries) are generally difficult to find and
meet their marketing objectives. ancestry do well in cage condi- may be expensive.
tions. This same research has
Size of catfish fingerlings to be
shown that many private hatch- Trout
stocked depends on the length of
eries, but certainly not all, have
growing season, availability, and Rainbow, brown, and brook trout
channel catfish strains that grow
marketing strategy. The minimum can all be reared in cages.
well in cages. Ask other cage pro-
size fingerling which can be Rainbow trout are most often cul-
ducers and use a strain that has a
stocked into a cage made of 1/2- tured because of the availability of
good reputation.
inch mesh is approximately 5 fingerlings, established market,
inches. Generally 6- to 8-inch fin- Stocking densities for catfish fin- and adaptability to cages. Basic
gerlings are stocked into cages. If gerlings in cages range from 5 to culture of all three species is simi-
a 1 1/4- to 1 1/2-pound fish is the 14 per cubic foot of cage. This lar. Rainbow trout will be
desired market size at harvest it equates to 250 to 600 fish in a 4 x 4 described here, but the informa-
may be necessary to stock a larger feet cylindrical cage. Generally tion should apply to other trout
fingerling or stock at a lower speaking it is best to stock at the species.
stocking rate. A larger fingerling low densities (5 to 8 per cubic
must be stocked in the northern foot) when first attempting cage
part of the southeastern region (or culture, particularly if supplemen-
at high elevations) where the tal aeration is not present. Do not
growing season is shorter. It is not stock below a density of 5 per
uncommon to stock 8- to 10-inch cubic foot or catfish may fight,
fingerlings where the growing leading to injury and disease.
season is 180 days or less. Some recommended stocking
Availability and cost of larger fin- rates for small cages are given in
gerlings may make stocking these Table 1. Even with supplemental
sizes prohibitive. A fingerling aeration available it may be
over 10 inches in length may not advantageous, for stress reasons,
adapt well to a cage. to stock additional cages rather Rainbow trout
than overstock individual cages.
Uniformity of fingerling size is
Overstocking can reduce growth Trout are coldwater species.
also important. Research has
and increase disease problems. Optimum growth temperature for
shown that catfish fingerlings of
uniform size (all within 1/2 inch trout is between 55 and 65oF, but
of the same length) will grow good growth is attained between
more homogeneously, reaching a Table 1. Recommended stock- 50 and 68oF. At 70oF severe heat
larger average size and increasing ing rates for cages. stress begins, usually followed by
total cage production over finger- death if exposure is prolonged.
Stocking Below 45oF feed conversion drops
lings with a 1 inch or longer vari- Cage Size Rates
ation in length. significantly and, therefore,
4 x 4 feet (round) 250 - 400 growth. These temperature
The strain or variety of channel regimes make cage culture of
catfish stocked into cages can 4 x 4 x 4 feet 320 - 500 trout a wintertime only activity in
make a great difference in pro- 8 x 4 x 4 feet 640 - 1,000 most of the southeastern United
duction or yield. Different strains 8 x 8 x 4 feet 1,280 - 2,000 States, except where cold spring
have been developed or selected water or high altitude lowers
at both public and private hatch- 6 x 12 x 4 feet 1,500 - 2,300
summertime water temperatures.
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It is necessary to stock a 6- to 8- readily, and have excellent flesh Striped bass temperature toler-
inch fingerling trout in most of the quality. For these reasons they ances and preferences are similar
Southeast to obtain 1/2- to 1- have been stocked all over the to those for channel catfish
pound trout by the end of the tropical world and probably rank (described previously). One
growing season. Stocking should as the most widely cultured tropi- observed problem with striped
begin in the fall as soon as the cal freshwater fish. In temperate bass is their poor growth and sur-
water temperature drops below climates, however, they cannot vival in soft water. Because of this,
65oF. Failure to harvest before survive winter water tempera- it is recommended that striped
water temperatures reach 70oF in tures. Optimum temperatures for bass and their hybrids should be
the spring will mean loss of your tilapia are from 80 to 90oF, but stocked in waters with total alka-
product and profit. good growth is maintained linity of at least 50 ppm. Stocking
Stocking densities for trout in between 75 and 95oF. Death densities recommended are the
cages may be a little higher than occurs at approximately 50 to 55oF same as given in Table 1.
those for catfish. The higher oxy- depending on the species, and
gen levels maintained by cooler diseases become common below
water and smaller sizes at harvest 60oF. Tilapia should not be
allow trout to be stocked at the stocked until the water tempera-
higher densities (Table 1) without ture reaches 70oF.
much concern for low dissolved Fingerlings should be stocked at 4
oxygen problems. In fact densities to 5 inches long (or larger) and
as high as 15 trout per cubic foot can be stocked at the densities
may be acceptable. described in Table 1. One distinct
advantage in the cage culture of
Tilapia tilapia is that they are unable to Striped bass
reproduce in cages and, therefore,
Several species of tilapia and their do not overpopulate the pond. At present the greatest problem in
hybrids have been reared in cages. Better growth is achieved if all- cage culture of striped bass is the
Species most often cultured are T. male populations are stocked. At availability of large or advanced
nilotica, Florida red tilapia, the lower stocking densities fingerlings. Most fingerlings are
Taiwanese red tilapia, Aurea red tilapia will have excellent feed sold at sizes too small to be
tilapia, and T. aurea. Some tilapia conversion because they filter feed stocked into cages. A minimum
species or hybrids are illegal or on plankton passing through the 4-inch fingerling is needed for
restricted in many states. Check cage. Tilapia should be harvested stocking and 8-inch fingerlings
with your state Department of before water temperature reaches would be preferable. Fingerlings
Natural Resources, Fish and 60oF. should be graded closely as canni-
Wildlife, or an Extension fisheries
Tilapia can be stocked in the same balism is a problem in young
(or aquaculture) specialist before
cage with channel catfish (called striped bass.
culturing these species.
polyculture). Research has shown
that tilapia polycultured with cat- Red drum
fish will increase catfish growth
because they stimulate the catfish The culture of red drum (redfish)
to feed more aggressively, increas- is a recent phenomenon. The
ing feed consumption. In polycul- research in cage culture of red
ture with catfish, tilapia should be drum is very limited. At present
stocked at rates between 1 and 3 temperature tolerances and pref-
tilapia per 10 catfish. erences of red drum appear to be
about the same as those for chan-
nel catfish (described previously),
Striped bass except that red drum do not
Striped bass and their hybrids appear to tolerate rapid tempera-
have been successfully reared in ture drops and require water of
Tilapia
cages. Striped bass are illegal or high alkalinity and total hardness.
restricted in many states. Check For this reason, harvest is recom-
Tilapia are truly a tropical fish mended before the temperature
with origins in central Africa. with your state Department of
Natural Resources, Fish and drops sharply in the late fall. Do
They tolerate high temperatures not overwinter these fish in cages.
well, can feed on plankton and Wildlife, or an Extension fisheries
detritus, are resistant to water (or aquaculture) specialist before At present the greatest problem
quality deterioration, reproduce culturing these species. with red drum, like hybrid striped
bass, is the availability of large
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fingerlings for stocking. The rec- were poor. The fish were fed a ers and can be placed in cages in
ommended stocking size is a 6- to high protein (43 percent) semi- nutrient rich ponds (eutrophic)
8-inch fingerling. Cannibalism is soft diet. More research needs to without any supplemental feed-
also a problem in red drum, so be conducted on the culture of ing. The reason for stocking grass
fingerlings need to be graded crappies in cages. carp in cages is to produce a larg-
closely. er fingerling for stocking into
recreational ponds (for weed con-
Bluegill trol) with large predatory fish.
Bluegill sunfish and their hybrids
have been reared in cages with
some success. Temperature toler-
ances and preferences of bluegill
are similar or slightly lower than
those for channel catfish
(described previously). Bluegill
are aggressive and will take food
at lower temperatures than catfish Crappie
and should be stocked before the
water temperatures reach 60oF. Carp
Limited research on bluegill cul-
Common carp (including German,
ture in cages has shown poor feed Carp
Israeli, mirror, and other varieties)
conversions.
have been successfully cultured in
cages and are commercially pro- One research study has been done
duced in cages in much of using silver x bighead carp
Europe, Asia and the Middle East. hybrids cultured in cages. The
Total production of common carp hybrids were stocked at densities
in cages is usually higher than of approximately two per cubic
that of most other species. It is not foot or 120 in 8 x 4 x 4 rectangular
uncommon to produce up to 400 cages. The cages were not fed and
pounds of common carp per cubic no artificial water circulation pro-
yard of cage. vided. These fish fed on plankton
and grew quickly from 10 inches
Chinese carp (grass, silver, big- to average 3.7 pounds in one
head, and silver x bighead growing season.
hybrids) also have been reared in
Bluegill cages. These Chinese carp are ille- Choose species carefully
gal or restricted in many states.
Fingerling bluegill/hybrids Check with your state Department Picking the fish species that will
should be 3 to 4 inches or larger at of Natural Resources, Fish and do well in cages in your particular
stocking and should be graded Wildlife, or an Extension fisheries location is important. For exam-
carefully to assure uniformity. (or aquaculture) specialist before ple, it is difficult to get enough
Stocking densities for bluegill culturing these species. growth on trout during the short
should be in the upper range of winters in Gulf coastal plain loca-
Common, grass, silver, and big-
those given in Table 1. tions but not in the longer winters
head carp (and silver x bighead
hybrids) have approximately the in states like Kentucky. Probably
Crappie same temperature preferences and the most important decision in
tolerances as channel catfish determining which species you
Limited research has been con- should culture in cages is: Is there
ducted on the cage culture of (described previously). Finger-
lings should be stocked into cages a market for them? Furthermore,
crappie (black, white and hybrids) is that market local or must they
in the Midwest. These crappie at a minimum of 4 to 5 inches in
length at the same stocking densi- be transported for long distances?
were captured from the wild then Is it a live market or a processed
transported and stocked into ties listed in Table 1. Common and
grass carp are usually fed a 32 to market? What size is preferred in
cages. Results of these preliminary the market? All potential produc-
studies indicate that black crappie 36 percent protein complete float-
ing pellet. Silver and bighead carp ers should evaluate markets
adapted best to cage conditions before selecting the species to be
but overall survival and growth (and their hybrid) are filter feed-
cultured.
The work reported in this publication was supported in part by the Southern Regional Aquaculture Center through Grant No. 94-38500-0045 from
the United States Department of Agriculture, Cooperative States Research, Education, and Extension Service.
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