Harvesting_Fish

SRAC Publication No. 394
II
Southern
Regional
Aquaculture
Center
November 1992
Harvesting Warmwater Fish
Gary L. Jensen1 and Martin W. Brunson2
Aquaculture is an established and
viable commercial agricultural
practice in many states. It includes
a variety of native and exotic species grown for human consumption, fish bait, recreational fishing
and hobby use. At some time in
the production cycle from brood
fish to marketing different live product forms, one or more life stages
of fish must be harvested from the
culture facility.
A successful fish farmer must
know how to keep fish alive and
healthy when they are moved. Different handling operations, like
harvesting, can trigger stress-related conditions in fish. Stress
from various handling practices
weakens fish and makes them
more susceptible to disease outbreaks and adverse physiological
imbalances. The sensitivity of fish
to stress associated with handling
varies among species. Some are
hardy, while others are extremely
delicate and sensitive to the smallest of stressors. Eggs and young
fish are more susceptible to sudden changes in their environment
than are older, larger fish.
plant. However, recent problems
in the catfish industry with red
spots and blotches in fillets, called
“red spot syndrome,” are thought
to be caused by stress incurred
during harvest and transport to
processing facilities. Therefore, it
is wise to take every stress prevention measure possible any time
fish are handled or harvested,
regardless of their destination.
Several methods can be used to
harvest fish efficiently and safely,
but careful planning is required
for a successful harvesting operation. Too often, ponds are seined
and only a few fish are caught be-
cause of improper harvesting techniques, poor pond design or insufficient planning. Consequently,
harvesting logistics should always
be considered in the design and
construction of aquaculture ponds.
The approximate number and
weight ranges of fish in ponds
should also be known or projected
so both the pond owner and buying customer are not disappointed
with a shortage of fish for delivery.
Pre-harvesting guidelines
Plan easy removal. Before planning the harvest operation, make
sure that fish can be removed eas-
More care and precautions are required during harvesting if fish
will be restocked into other facilities for further growout rather
than sent to a nearby processing
1
2
Louisiana Cooperative Extension Service
Cooperative Extension Service, Mississippi
State University
Fish basket on boom truck for moving fish from pond to truck.
1
ily from the production unit. If a
cage or raceway is used to growout fish, then harvesting is somewhat simplified and fish numbers
and weights should be known.
However, when fish are in a large
pond, several factors can delay or
stop harvesting. Also, an inventory of fish stocks is more difficult
to maintain when a pond has been
in continuous production for several years. In such systems, larger
fish are “topped” and smaller fish
have been understocked, resulting
in a wide diversity of sizes of fish
in the pond.
Avoid debris and delays. First,
check for debris on the pond bottom that will snag the seine or livecar. Aquatic plants may not be
visible at the water surface, but
may be growing at or near the
pond bottom. These plants can
cause the net to roll up at the bottom and may make seine dragging
impossible. Fish can be killed if
they are entrapped in aquatic
weeds during harvest. Nuisance
weeds should be controlled before
harvesting is scheduled. During an
unexpected delay in harvesting,
fish prices may change, an off-flavor condition may develop, and
the crop may have to be held into
the next growing season, seriously
impacting cash flows. So, avoid unnecessary delays that may be
costly.
Take samples. It is important to
know what’s in your pond before
harvest. Sample fish with a short
seine, cast net, lift net or snag
hooks, depending on species.
Keep records of fish numbers and
amounts of feed consumed. Ensure that the quantity of fish expected to be harvested can be
marketed. Otherwise, you may
have to release many fish after expending considerable time and
labor. The harvesting operation
may severely stress fish after they
are trapped, crowded and held.
Release of these fish back into the
pond or culture facility can markedly affect their mortality risk.
Check fish health. It is essential
that fish are healthy and in good
condition before being harvested.
Signs of good condition include
good feeding appetites, no mortalities and no obvious external problems. A sample of fish can be
examined by a qualified fish
health specialist to determine if
any obvious health-related problems exist. This does not mean that
fish are certified to be disease free,
but it does provide more information to determine the condition of
fish stocks. If sick fish are handled,
the added stress can trigger a disease outbreak that can cause high
mortalities.
Try to pick favorable conditions.
You should have adequate labor,
equipment and supplies available
for harvesting. Weather and water
quality conditions may also be important. On many farms, foodsized fish for processors are
harvested regardless of the
weather. Only thick ice on ponds
may stop some harvesting operations. Movement of large trucks
and harvesting equipment can rut
and damage levee tops that are excessively wet and lack protective
cover such as gravel. In severe
cases, equipment may not even be
able to reach ponds because of the
poor condition of access roads or
levee tops. Main levees should
have a gravel cover that provides
an all-weather surface.
Stop feeding. Take fish off feed before they are harvested. Withdrawal varies from one to two
days during summer, to three or
more days during winter. This is
especially true if fish will be transported long distances. Undigested
food can be regurgitated in the
transport tank and foul the water
quality. Fish are also hardier and
less stress occurs when their stomachs are empty. If food fish have
been fed medicated feed, be sure
that the proper withdrawal time
has passed before they are harvested for processing. A 21-day
withdrawal period is required for
Terramycin ® medicated feeds and
three days for feeds containing prescribed levels of Romet® for catfish. Water quality conditions
should be good during harvest. Beware of possible low oxygen con-
2
centrations when fish are harvested at or shortly after sunrise.
Check for hydrogen sulfide. In
deep water ponds, hydrogen sulfide can accumulate in oxygen-deficient bottom muds and may be
released upon disturbance of the
pond bottom. This gas is highly
toxic to fish and can be detected
by a smell similiar to that of rotten
eggs. If unsure about this condition, stir up the mud around the
proposed harvesting site to determine if a potential problem exists.
If a rotten egg smell is noticed,
find another suitable site. Stir up
the site to release the gas before
harvesting or treat with potassium
permanganate to oxidize the gas.
This condition is seldom a problem in shallow, warmwater fish
ponds.
Check temperatures. Harvest sensitive species during the early
morning when water temperatures are lower and sunlight is less
intense. Some fish, like golden
shiners, striped bass and the
striped bass hybrids, are harvested
most successfully at water temperature less than 65°F to minimize stress and fish losses. They
require special handling during
harvest at higher temperatures.
Fish should be moved quickly
from ponds to buckets or transport
tanks in freezing, windy weather.
Exposure to sudden temperature
changes can shock fish, especially
small ones.
Investigate custom harvesting. In
some areas, harvesting can be contracted. The custom harvester supplies the labor, equipment and
expertise. Cost is based on the
total pounds of fish harvested and
possibly a distance factor. Producers may also cooperate in a local
area by sharing labor and capital
for harvesting purposes. Many
farms have their own harvesting
capability when harvesting is frequent or self-sufficiency is needed
because of the unavailability of
custom services. Purchase of specialized harvesting equipment
should be cost beneficial, and adequate labor is essential.
Basic equipment
There is a variety of harvesting
equipment used in the commercial
fish farming industry. Various
nets are available for harvesting,
in addition to specialized equipment that includes livecars, boom
trucks, loading baskets, fish
pumps, boat with outboard motor,
and other items. The choice of
equipment depends on the size of
the operation, available labor, frequency of use, available capital,
preferred harvest method, volume
and sizes of fish harvested, and
species considerations.
Cast nets. These are inexpensive
and useful for sampling. Cast nets
are made of monofilament nylon,
and the mesh size should be
matched to the species harvested.
Fish with spines entangle easily.
With practice and patience, anybody can throw a cast net properly.
Lift nets. Bait minnow and tropical fish producers may use lift nets
to capture small numbers of fish.
These nets are made of soft, small
mesh that minimizes injury. Fish
are lured into the trapping area
with feed, and the net is lifted
quickly when fish are evident. The
lift net and its assembly are portable.
Short seines. Short 10- to 20-foot
long “Commonsense” minnow
seines work well to harvest fry in
tight schools. Seines can be pulled
manually by two persons or can
be shortened and used like a dip
net from a boat. The water should
be clear. Once fry break out of
schools and scatter, a V-trap can
be used for harvest of small, delicate fry.
Success depends upon knowing
the habits of fish and locating the
trap properly. The V-trap usually
has glass or fine mesh sides that
form a narrow vertical opening
that fish enter. A lead panel may
extend from one or both sides of
the mouth to guide fish into the
opening as they move along the
pond bank. Set the trap so fry
swim between it and the shore.
The lead panel intercepts fry and
leads them into the trap. Use a dip
net to harvest fish daily (or as
often as necessary depending
upon species) from the boxshaped trap.
Gill nets. These can be used in
ponds to harvest large fish selectively or a few at a time. They are
normally strung across a pond.
They are made of clear, monofilament nylon that makes them difficult for fish to detect. Floats are
used to mark their location, and
each end is anchored. Nets can be
totally submerged or extended
from the surface to the pond bottom. Fish can be driven into the
net by a boat to increase the catch.
Gill nets work best at night when
less visible, and should be checked
frequently because fish caught usually die. They can also be eaten or
damaged by turtles or other predators.
Large seines. The most common
type of harvesting equipment is
the seine or harvesting net. Seines
work well in large regular-shaped
ponds with relatively flat, unobstructed bottoms. Ponds that can
be harvested without draining are
called seine-through ponds. No
water is drained for seining typical
levee type ponds, but in some embankment ponds water levels are
lowered to facilitate harvest.
Net features
Mesh size. Select the proper mesh
size to harvest fish of the desired
size. Fish shouldn’t go through, be
gilled or become entangled in the
net. Raschel nylon mesh is available in various sizes and is recommended for fingerlings 4 inches or
smaller.
Small mesh seines are harder to
pull because of more resistance.
Also, mud does not sift through
them as readily. Seine length
should be one and one-half times
the widest part of the pond. This
assures enough length to keep the
weighted line on the pond bottom
and levee toe as the seine is pulled.
The depth of the seine should also
be one and one-half times the
maximum water depth. For large
commercial catfish ponds, seines
may be longer than 1,000 feet.
3
Because of such weight, tractors
are used to pull them.
Texture. Net texture is determined
by the material and how the mesh
is formed, either with knots or
woven. Nylon nets should be
coated with a resin or asphaltbased net preservative to prevent
catfish from getting caught by
their spines. Polyethylene nets require no coating treatment. Knotted net is suitable for catfish, but
most scaled fish require soft, uncoated knotless nets. These nets
limit injuries from scale loss
caused by abrasions. Carp or buffalo fish, however, can be harvested with knotted nets. Number
42 nylon twine is recommended
for catfish and other large fish to
provide adequate strength. Net
manufacturers can recommend the
proper size, number and distance
interval between floats.
Bottom line. The bottom line, or
mudline, of the seine can have a
many-ends sisal mudline, 2-inch
diameter mudline of knotless
mesh nylon netting or hard rubber
rollers. The design affects how
deep the bottom line digs into the
pond bottom and its ease of pulling. Evaluation studies of various
mudline designs indicate that roller-mudline equipped seines are
preferred when harvesting foodsized channel catfish from ponds
with irregular bottoms consisting
of deep, soft muds. The meshmudline is recommended when
harvesting channel catfish from
ponds with hard bottoms or harvesting fingerlings because of its
lighter weight and tendency to
clear mud.
Seine reels
A hydraulically operated seine
reel is often used to transport,
store and beach the seine. There
are various models and sizes. Most
are single reels, but some have
two. The smaller second reel hauls
in the loose end of the seine when
fish are funneled into a sock or
livecar. With the single reel, the
loose end is landed manually. A
standard 5-foot reel can store
seines as long as 1,200 feet. The
or dump the mud from the seine
so that fish do not escape. A 14foot boat with a 25-horsepower
outboard motor is adequate. A
chemical boat also works well and
has ample space for carrying a livecar. Pull the seine slowly with a
zig-zag motion at about 25 to 45
feet per minute to prevent the
seine from lifting off the bottom.
Seines will have to be pulled over
or pushed under aerators, depending on how they are anchored.
Hydraulic seine reel used in seining large ponds.
reel is mounted on a trailer. Some
have hydraulic controls that pivot
the reel into various positions to
line up with the seine as it is
landed.
Basic harvesting operation
Seine crew. Five to seven persons
form a seining crew for large
ponds. Two to four persons inside
the pond keep the weighted line
on the bottom near each levee toe,
two drive the tractors, and one operates a boat to dump mud from
the bottom line. An experienced
crew can seine a large pond and
concentrate fish in one to two
hours.
Seining technique. The shape of
the pond determines how it
should be seined. Usually the
proper length of seine is stretched
across the narrow end of the pond
in front of the drain structure: A
bracket on the bow of the boat, or
the float line laid over the bow,
helps push the seine as it collects
mud. Watch the float line for indications that the net is “mudding
up.” The floats will be pulled underwater if this occurs. The seine
boat should quickly move to roll
Seines can be pulled manually or
with small tractors, trucks or fourwheelers in small ponds less than
several acres. A seine longer than
several hundred feet, however, is
difficult to pull manually in ponds
with soft, muddy bottoms. A bag
that is woven into the seine is a
nice feature for small seines. It
provides a good area to capture,
hold and harvest fish.
Land the seine near a water supply or aerator where fresh, oxygenated water can be provided if
needed. When fish are crowded,
they can rapidly deplete the dissolved oxygen in a localized area,
especially in warm weather.
Holding fish. A device called a
livecar, or sock, is used to crowd
and hold fish. Attach it to the seine
after fish are crowded with the har-
I
Boom truck used for loading fish from pond onto hauling
truck
Seining boat for working large seines.
4
seine. Do not use a livecar. Pull a
short cutting seine of the desired
mesh through the fish to roughly
grade and concentrate them for
loading. If fish require overnight
holding, leave them in the larger
area of the staked harvesting seine.
Livecar (sock) used for holding fish after seining.
vesting seine. This lessens the
chance of the livecar hanging up
on snags and decreases the pulling
drag. A short piece of rope ties off
the funnel end of the harvesting
seine until the livecar is attached.
The livecar has a metal loading
frame which attaches to the seine
with drawstrings. The metal loading frame sets up a narrow chute
to funnel fish into the livecar as
the seine is beached. Without the
chute, many fish can remain in the
seine as it is landed. They will then
be much harder to move into the
livecar.
Water should beat least 2 ½ to 3
feet deep for easy fish transfer. If
water temperatures are below
60°F, fish can be held many hours
and overnight. However, if temperatures are in the low 80s or
higher, fish should beheld only
for a short time and carefully
monitored. Water temperatures affect fish activity and ease of grading in socks before harvesting. Use
one mesh size larger than normal,
and allow overnight grading before harvesting fish in winter. This
will avoid harvesting many offsized, unmarketable fish. The sock
needs to be in good condition or
fish will escape overnight. Hauling trucks can be scheduled with
assurance when fish are held in
livecars.
Minimize stress. When holding
fish, move the sock to deeper
water to provide more room and
clearer water. In warm or hot
weather, it is helpful to cool fish
before harvest by moving the sock
near a flowing well but not under
it or directly in the high current
area. Fish in socks are usually so
crowded that little water movement takes place within the sock,
and the increased current probably stresses the fish on the exterior of the sock as they constantly
swim against the current. Harvesting stakes can be used to secure
the lead line into the pond bottom
and hold the float line about 1 foot
above the water surface. If the
sock if not properly anchored, currents from a well or an aerator can
roll up the livecar and kill fish.
Also, beware of the possibility of
theft when fish are held overnight.
Livecars are more secure for holding catfish than seines because
they have a solid mesh bottom
and double float line that prevent
fish from jumping out. Fish are
good escape artists. Several livecars may be required if many fish
are harvested. About 5,000 pounds
of fish can be held in each 10-foot
length of a standard-sized sock at
temperatures below 80°F. The increasing frequency of “red fillet
syndrome” in catfish is thought to
be directly related to harvest and
holding stressors.
If fish must be landed in shallow
water, or a large number must be
harvested, consider another harvest method. Harvest fish as before, but stake out the harvesting
5
Watershed ponds. Harvesting is
more difficult in watershed ponds
because pond depths are usually
more than 10 feet. Obstacles are
common in bottoms and on banks.
Fresh water is usually absent at
the harvesting site. Watershed
ponds usually have to be drained
to a smaller area with a maximum
depth of 6 to 8 feet. The height
from the harvesting area to the
levee top makes loading a transport truck difficult and time consuming without the use of
mechanized equipment. Ideally,
fish are harvested in colder
months so stress on fish is less and
ponds can refill with runoff water
during late winter and early
spring.
Most baitfish are harvested by
seining because it is faster than
using lift nets. Fish are crowded
into the bag portion of the seine,
then the bag is staked. Minnows
are dip netted into floating holding boxes with nylon walls. Summer harvests are stressful because
of warm surface waters. Pumping
cool well water near the harvesting operation helps reduce stress
and losses. Minnows are harvested
frequently to keep up with customer orders.
When manually beaching a seine,
pull it slowly and carefully to keep
the lead line on the pond bottom.
Too often there is an unnecessary
rush to land the seine, and many
fish escape under the lead line
when it is accidentally lifted off
the bottom. Four persons can
beach a seine. Two pull in each of
the loose ends. One keeps the lead
line on the bottom, and the other
helps pull and piles the seine on
the bank. When the lead line is on
shore, raise it and close off both
ends by slipping your arm under
the seine and lifting it out of the
water. This forms a hammock
shape that traps fish. Concentrate
fish into the middle, and move the
seine to deeper water to stake it if
desired. Harvesting stakes free up
labor to move fish rather than just
hold the seine.
Fish pumps
A fish pump can be used for harvesting. There are various models.
They move fish rapidly and safely
from tanks or ponds to hauling
trucks. Crowding is required, then
the pump intake is placed where it
can move fish and water to a dewatering tower or box. The water
returns to the ponds, and fish are
loaded into the transport tank.
Pumps can be portable units
mounted on trailers or fixed units
mounted on a transport truck.
They are commonly used in the
trout industry and are being evaluated for use with warmwater species.
moved from spawning boxes and
transported to hatcheries for incubation. To remove the eggs, use a
wide blade scraper or putty knife
to loosen the adhesive egg mass
from the bottom of the spawning
container. Gently raise the box toward the shallowest water along
the bank so the eggs can be more
easily retrieved if they fall out of
the box.
Remove the eggs with your hand,
and put them into a plastic fish
basket that has mesh openings.
The basket can be placed inside an
inner tube for flotation. The openings allow water to pass freely
through the basket as it is pulled
from box to box. Tie a rope between the egg collection container
and your belt or pants’ belt loop to
pull the container as you walk to
check spawning boxes, and keep
your hands free.
The use of fish pumps often means
fish weights are determined by
water displacement rather than
with scales. This weighing method
is less stressful on fish than scale
weighing and can be accomplished quickly. One pound of
water is displaced by 1.02 pounds
of fish, and 1 gallon of water
weighs 8.35 pounds. To determine
fish weights by water displacement, just determine the change in
water volume in gallons in the
transport tank after fish are loaded
and use a simple formula.
Tubs or ice chests can also be used,
but they are less suitable. Water
can warm more quickly and water
quality can deteriorate faster unless eggs are emptied frequently
and the water is replenished. Do
not hold eggs in stagnant water
during collection for more than 15
minutes without aeration or adding fresh, clean water. Make sure
all pieces of the egg mass are removed from the spawning box so
the male catfish can service another female, rather than care for a
small fragment of eggs.
For example, if loaded fish increase (displace) the water volume
in a tank by 50 gallons, then the
weight of fish is equal to 50 gallons x 8.35 pounds/gallon x 1.02
or 425.8 pounds. A water displacement tube on the outside of the
tank, or a clear viewing plate in
the tank wall, can be used to calculate the amount of water displaced. This is a new technique for
most warmwater fish farmers but
offers some real advantages and
promise.
Yolk-sac fry can be harvested from
incubation troughs by siphoning
with a 1/2 inch-diameter clear
plastic hose. Siphon fry into a dip
net or strainer that is submerged
in a bucket of clean water. The fry
can now be quickly stocked into a
rearing trough. To harvest older
swim-up fry, use a fine mesh
aquarium dip net to transfer them
from the rearing trough to a
bucket of clean water for stocking
into a transport tank. Always
move small fish in a cushion of
water, and minimize their time out
of water.
Harvesting eggs and fry
Besides food-sized and fingerling
fish, there are situations when
eggs and fry require harvesting.
Catfish egg masses are usually re-
6
Harvesting situations and
options
There are three harvesting situations to consider:
■ Partial harvesting exists where
only part of the fish are removed.
■ The pond may also be topped
where larger market-size fish
are selectively harvested from
ponds with mixed fish sizes.
■ Finally, the pond maybe clean
cropped, where all fish are harvested.
The only reliable way to harvest
all fish from a pond is to drain it
completely. This involves a combination of draining and seining.
Avoid using a seine in very shallow water because it stirs up the
mud and causes low dissolved
oxygen and high toxic gas conditions which can be extremely
stressful to fish. Shallow water can
also warm quickly in hot weather.
Seine trapping relies on feed to attract fish into a trapping area. A
seine at least 200 feet long works
well. Locate the seine parallel to
the pond bank or across a corner
about 50 feet from shore. A pull
rope attached to each end is staked
on the bank for easy retrieval. The
trapping area should have a firm
bottom, be free of any debris and
be less than 5 feet deep. Catfish
and other species may be shy initially, but can be lured into the
trapping area by feeding outside
the open end of the corral seine
and drawing them in with a trail
of feed. Use floating feed to observe feeding activity. Feed routinely at the time you intend to
harvest. Do not alter your feeding
activity on harvest day, except for
using less feed.
To harvest, simply pull the coiled
seine ends to shore. Drag the seine
carefully to shore to concentrate
fish. Have enough labor available
to keep the bottom line on the
pond bottom while dragging the
seine to shore. Trapping success in
the same area requires a 7-to 14day recovery time before fish lose
their shyness and the operation
can be repeated. Because of the importance of baiting with feeds, this
method is more effective during
warm weather when fish are feeding actively.
Many catfish producers prefer to
top their ponds by harvesting
larger market-sized fish in a population of mixed fish sizes. This
method works best in seinethrough ponds that require no
draining. The same pond may
have fish harvested three or more
times yearly. Fish are harvested
when sufficient numbers reach
market size. This may be 1,500 or
more pounds per acre in large 10to 20-acre commercial ponds. Harvesting efficiency in seine-through
ponds should be about 70 percent
to 90 percent of the harvestable
sized fish, depending on species,
size, experience of harvesters, and
the condition of the pond and harvesting equipment. Catfish can create large craters in pond bottoms
that can become extensive after
continuous production of 4 or
more years. These depressions
probably reduce harvest rates.
However, there is considerable
controversy over how often a
pond should be clean cropped and
renovated to restore fish inventories and repair pond bottoms and
levees,
Other trapping methods include
large lift nets and drop nets, but
they are usually not as effective.
The lift net covers too small an
area, and repeated use can reduce
fish production. Catches with the
drop net decrease considerably
after the initial catch.
In ponds used for fingerling production, especially when raising
delicate fish species, harvesting
kettles or basins are common features. They are made of poured
concrete and have several openings with vertical grooves for
placement of wood tongue and
groove boards to adjust water levels inside the basin. These areas
are located in front of the drain
structure, and their bottom is the
same elevation as the bottom of
the drainpipe. A water supply
pipe is often located near the basin
to furnish fresh, oxygenated water
as needed. Concrete steps from the
basin to the levee top make it easier to carry tubs or buckets of fish
and water. Before fish are concentrated, the basin should be cleaned
with a broom or other device
while the drain is open to remove
any mud or sediment that can accumulate in the area. The harvest
basin is usually found inside the
pond, but outside kettles also
exist. Fish are usually dip netted
from the basin and placed in buckets of fresh water. These structures
are common in government hatchery ponds that frequently harvest
small fingerlings of game fish species.
Removal from ponds
When fish are moved from ponds,
they are commonly lifted with a
loading basket attached to a hydraulic boom. The fish are first
crowded in a livecar or cutting
seine. The boom can be mounted
on a special truck. A front-end
loader or backhoe will also work
well with a few modifications, including an extension pipe. The
loading basket is designed so fish
drop through a trap door with an
easy, safe release. The basket can
move 500 pounds or more per
load. Weights are determined with
in-line, spring-loaded or electronic
scales. The loading basket net
should be treated with a coating if
used for catfish. Do not overload
the basket if fish will be restocked
or hauled on a long trip. Make
sure people are clear of the swinging basket as it moves and nobody
is underneath it.
Another method of harvesting fish
involves dip netting fish into buckets or tubs filled with clean water.
Fish should be moved quickly and
should not be overloaded. Water
quality deteriorates rapidly when
fish are concentrated, especially in
warm weather. A bucket-brigade
helps reduce the strain and work
of heavy lifting. Remember, one
gallon of water weighs 8.35
pounds! This method works well
for small, delicate fish where special harvesting precautions are re-
7
quired, but it can be time consuming if many fish are harvested.
Seine maintenance
Seine storage and care are important to prolong the life of equipment. Uncoated nylon seines are
damaged by direct sunlight. Remove dead fish that can attract
rats, which damage seines. Short
seines should be hung in a covered site and air-dried. Never store
a damp and unclean seine in a
heap. Some aquatic weeds, parasites and infectious diseases may
be transferred from pond to pond
by harvesting equipment. For this
reason, remove any fish or nuisance aquatic weed fragments. Airdrying the seine can kill most
parasites. Diseases such as bacterial ESC may remain alive in moist
mud balls not cleaned from seines.
Repair any holes in the seine as
soon as they are detected in order
to maintain the equipment in
workable condition and ready for
use.
Summary
Fish harvesting is an important
step in getting fish out of production facilities in good condition so
their survival and quality for other
uses are assured. Experience and
common sense will be valuable factors to assure success. Take time to
plan properly before putting nets
into the water. Do not forget that
fish are sensitive to handling, and
that harvesting is the first stress of
more to come if fish will be
graded, held, transported and restocked. It takes a higher quality
fish to live after harvesting compared to one that will shortly be
processed.
Additional information
For information on sorting and
grading warmwater fish refer to
SRAC Publication No. 391. Detailed information on transporting
warmwater fish can be found in
SRAC Publications 390, 392 and
393. For additional information or
assistance on this subject, contact
your local office of the Cooperative Extension Service.
The work reported in this publication was supported in part by the Southern Regional Aquaculture Center through Grant No. 89-38500-4516 from the United
States Department of Agriculture.
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