Fishing systems and harvesting machines

Fishing Systems and
Harvesting Machines
Swagatika Sahoo
PG Scholar

Contents
2
• What is Fishing system ?
• Mechanised harvesting and steps
• Different machines used for harvesting in fish culture
• Important harvesting machine systems
(1) fish pumps
(2) hydraulic dredges with pump and conveyors
(3) harvesting machine for seaweeds
(4) fully automatic longline systems

What is fishing ?
3
Fishing / fish harvesting : the act of catching fish or other aquatic animals from its wild habitats with or
without use of fishing vessel.
Fishing
vessel
Fishing
gear
Fish
harvesting
system
Traditional methods of fish harvesting are Ring seine, Stake net, Chinese dip net, Cast net, Shore
seine, Trammel net, Mini trawls, Gill nets, Hook and line, traps and pots.
System : a set of things working together as parts of a mechanism or an interconnecting network; a
complex whole.
What is system?

4
• So fishing system is the combination of
the observations and handling methods
before, during and after the catch. It is
also referred as an integrated fishing
system.
• This system will be steered by computers
being used to collect and to evaluate data,
and to apply fully automatic fishing
methods combining searching, catching
and processing, so bringing the optimum
of success.
• fishing with modern computerized systems
is also fishing system.
Modern methods of fish harvesting include Trawling, Purse seining, Gill net, Hook and line
mechanized, Jigging and Trolling lines.
Fig. Automated unmanned fishing system

5
• This system includes not only the computerized operation of the vessel’s engine, and of the fish
processing plant on board, but includes also fish searching, fish identification, and the selection
of the catch.
• The system also includes all the navigation required to bring the vessel and gear into the best
position in relation to the prey desired to be caught. Computers will calculate the right time to
shoot the gear, in order to control the catching process and the quantity of fish caught.
• Finally, the system includes automatic hauling of the gear and the handling of the catch for
processing.
All this can be realized only on the assumption that
•Exclusive Economic Zone (EEZs) rules, fishing rights
•Variation in needs of international markets
•new ideas about the protection of nature,
•the increasing price of energy
Do not stop or change the direction of fisheries
development.

Why Automation is in fisheries ?
6
o The total industrial activity associated with the harvesting operations, product processing
(offshore and onshore), and the aquaculture-based fish farming are subject to strict demands
by national and international level.
o Hence ,productivity of processes in terms of the resources used (manpower, capital, energy
and feed) to produce the products, quality of products set up by the international competition,
and impact upon the environment is very important to consider.
o The best available technology must be employed to meet these demands.
o Among the key technologies that can offer progress in both productivity and quality are
mechanization, instrumentation, computer-based sequential control and automatic feedback
control. All these technologies will for convenience be referred to as Automation.

7
The establishment of effective
operational control
procedures, development and
testing of the software
required to operate the system,
and troubleshooting and
identifying problems will
represent the critical factors in
system
Advantages
Disadvantages
•Cost effective harvesting
•Fuel savings
•Reduced manpower
•Direct processing facilities
reduce pollutions on shore

8
Automated fishing system- a gulf of Mexico case study
• There are an estimated 1,000 unused oil rig
platforms and structures in the Gulf of Mexico
and several thousand more which are oil
producing units.
• Recreational fishermen have demonstrated the
usefulness of these platforms as attractors of
food fish such as red snapper, lemonfish,
grouper, and drum, and it is known that coastal
pelagic fish are also attracted in great numbers.
• These platforms are the integral component of
the automated unmanned fish harvesting
system, although in areas without such
platforms groups of man-made underwater
structures could be used.
Figure. Artist’s concept of an automated fishing station
on an offshore oil platform

9
SYSTEM COMPONENTS
1. Attraction Devices
• From research it is found that pelagic fish are attracted more to submerged three-dimensional
structures, resembling small tents, than to horizontal or vertical plane surfaces.
• Field studies reported that Multiple lights, properly spaced, appeared to act as independent
attraction points and it was demonstrated that fish attracted to one could be led by sequentially
illuminating the series of lights. A single moving light also proved successful in leading fish. Use of
artificial structures in conjunction with light attraction significantly increased the density of fish
concentration.

10
• It is reported that guiding or leading coastal pelagic fish to
the anode was easily accomplished within a uniform
electric field. Nonuniform fields caused the fish at the
outer edges to undergo a fright reaction because of the
low voltage gradient.
2. Control techniques
• Laboratory experiments identified that electrical
characteristics needed to induce electro taxis as a means
of controlling and leading fish.
• A modified electric shrimp pulse generator was used
which produced pulsed direct current in the form of
capacitor discharges at a rate of 5-75/second.

11
• Fish in the center of the field underwent electrotaxis and swam toward the anode
until the voltage increased sufficiently to cause tetanus.
• Fright and tetanus responses are undesirable for leading fish; however, fish can be
led considerable distances without these responses in a uniform field. Thus an
electrode array should be designed to produce an electric field as close to uniform
as is possible in the area where electrotaxis is wanted.
• The behavior of fish in an electrical field is dependent on the voltage applied, pulse
rate, and length of the animal, since the voltage potential increases proportionately
with length.

12
1- input/compensating pulse
capacitors and rectifier unit
2- output transformer
3- main control unit
4- a composite picture
including the variable input
transformer in background.
1 2
4
3

13
A minicomputer would be necessary at each site to properly activate the concentrating and
holding lights. The lights would be automatically turned on about sundown and, if a series of
satellite structures were used, the computer would also activate sequential lights to lead fish
from the satellite structures to the main platform. The fish would be held by the main light for
harvest by the processing vessel.
3. Pumping and processing equipment
• Fishes are generally pumped by suction pumps to the deck or directly to the processing factory on
board.
• The pumping and processing equipments with adaptation of an electrode array and possibly a small
secondary pulse generator around the pump intake is required to complete the automated fishing
system.
• It would also expedite transfer and handling of the product between the platform and service vessel
and at the shore facility.

Mechanized harvesting
in fish culture
14

Harvesting is a complex operation that can be divided into into
three major parts, as follows:
15
o Driving and concentrating the fish stock to the catch basin (HERDING OPERATIONS)
⦿ lifting the fish out of the catch basin and placing them on a sorting table (CATCHING
OPERATIONS)
⦿ sorting the fish and loading them on the transporting vehicle
 Mechanical Fish Lifting
 Hydraulic Fish Lifting
• Mechanical Driving by different nets
• Hydraulic Driving i.e., draining fish with water
• Electrical Driving by electric grid

16
Herding operations
1. Mechanical Driving
• The mechanical driving of the fish by seines is the most used method. When the
fishpond is large, the netting should be mechanized because of the high pulling force.
• In some cases, conventional motorboats, tractors or trucks can be applied for pulling
the net, but special winches have been developed for this purpose .
Fig. double drum seine pulling winch
Schematic of haul seining procedures by winch
with 2 drums (USA)

18
2. Hydraulic Driving
During hydraulic driving the fish are carried from the pond into the catch basin by water
current as the water is draining from the pond. The pond and the drainage canal should
be drained completely.
3. Electrical Driving
• Electric grids or electrified seines can also be used for driving, where the electric field forces the
fish to swim towards the catch basin.
The electrode system of a electric fish
driving device

Catching operations
19
Mechanical fish lifting can be classified as follows:
• devices with intermittent operation
(a) mechanized dip net
(b) bucket with alternate movement
• devices with continuous operation
(a) conveyor belt
(b) screw
• Lifting the fish out of the catch basin is a critical process because the fish are separated from their
natural living medium: therefore, gentle handling is needed.
• Moreover, this process has to be intermeshed with the driving of fish into the catch basin and with
sorting and transporting.
• Different lifting devices have been developed for fish harvesting, but the two major groups are
mechanical and hydraulic devices.

(a) Mechanised dip net
Mechanized dip nets are usually a mobile type of equipment and can be used widely, but
two or three men are needed for the operation
20
Figure. a mechanized dip net.
Device with intermittent operation

22
(b) Bucket with alternate movement
The fish can be lifted out of the catch basin by a mechanized bucket elevator. One man can operate
this device with a control panel, but its installation is fairly complicated.
fig. Mobile bucket elevator (USSR)

23
• Ordinary agricultural conveyor belts can be
used for fish lifting as well, but specially
designed conveyor belts have also been
developed with soft rubber belts and covers .
• These belts are mobile equipment and can
be widely used, especially when the fish
have to be lifted up to a fairly high elevation.
• The lower hopper of the belts can be filled by
hand or by some device like a mechanized
dip net, air lift pump, etc
• A mobile fish conveyor belt or fish screw is
the most efficient method of loading the fish
from the sorting table to the transporting
vehicle.
Continuous operation- (a) conveyor belts
Fig. Belt conveyor for fish lifting

25
• Special fish screws have been developed recently for lifting fish.
• The internal spiral ribbon and the pipe housing revolve together lifting up the water in the space
between the spiral ribbon and the housing.
• The applicability of the fish screws is the same as that of fish conveyor belts. However, the
screw makes for more careful fish handling since the fish are lifted in water.
(b) Fish Screws
Fig. screws for fish lifting

26
Hydraulic Fish Lifting
• The working principle of hydraulic fish lifting is basically different from that of
mechanical lifting, as it is the water which is lifted directly and not the fish.
Hydraulic fish lifting devices are usually water pumps which have been modified
according to the special needs of fish lifting.
• Hydraulic fish lifting devices or fish pumps can be divided into three groups, as
follows
(a) centrifugal fish pumps
(b) air lift pumps
(c) vacuum pumps

27
• Recently, well designed centrifugal fish pumps
became available and are commonly used,
mostly in trout farms. However the size of the
fish is limited when using a centrifugal fish
pump.
• Centrifugal fish pumps were first used in marine
fishing vessels and, later on, in pond fish farming.
• These centrifugal pumps caused serious damage
(2-5% of catch) to the harvested fish by their
impellers .
• Special impellers were later developed and the
damage to the fish decreased.
(a) Centrifugal pumps
Fig. working of centrifugal pump

(b) Airlift pumps
28
• Air lift pumps are used in water management for delivery of water containing solid particles.
• The principle was adapted successfully for fish lifting, and special air lift pumps have been
designed. Even big fish can be lifted without any damage, as there is no moving part inside
the delivery pipe, only air bubbles.
Fig. mechanism of airlift pump

29
The operation of vacuum pumps is
intermittent and they can, therefore, be used
most efficiently in small units (cages) where
the whole stock can be sucked into the
container during one cycle.
(c) Vacuum pumps
Vacuum pump for fish harvest

Fish sorting
31
• The harvested fish stock can be sorted according to size (thickness) and, in polyculture, according
to species.
• The fish can be sorted into size by different screens. The screen can have several pairs of ribs with
an increasing distance from top to bottom .
• The distance between two ribs is adjustable according to the grading requirement. There are
graders where, instead of having fixed ribs, revolving rollers are used.
fish grader having fixed ribs Fish grader Type with rollers

32
Harvesting machines include comparatively new types of sophisticated gear that may
mechanically separate the fish or shellfish from the water by Pumps (pump fishing) or by
mechanized dredges, as well as floating machines that dig out mollusks by means of
underwater jets (hydraulic dredges) and transport them out of the water with the help of
conveyor belts.
The harvesting machines commonly used are
1. Fish pumps
2. Hydraulic dredges with pumps and conveyors
3. Harvesting machines for aquatic weeds
4. Automatic longline systems
Harvesting Machines

34
o The use of suction pumps to catch fish, shrimp, squid, krill or plankton without the use of nets is
called ‘pump fishing’. This so-called ‘pump fishing’ is mostly done with light and electricity.
o There are two problems to face in pumping fish:
(1) the size of the fish in relation to the diameter of the hose
(2) the rate of damage to the fish.
o To operate pumps economically in fishing, without any other gear, needs a high concentration of
prey near the water surface. Moreover, the concentrated prey must not be frightened by the
water current caused by the suction of the pump.
o The fish can be pumped from depths of up to 110 m. The hose has an inside diameter of 20 cm. On
the vessel a separator removes the water and most of the fish scales.
Pump Fishing
The diameter of the hose used for pumping must be
limited, therefore only small fish can be pumped.
If the fish are to be used to produce fish meal and not for
human consumption, the rate of damage is not important.

35
The fish are attracted by light
from the depths to the area of
the pump
They are concentrated and
narcotized by electric currents
the outer area of the electrical
field has a frightening effect
on the fish; only the fish inside
a small area are attracted and
stunned.

In the Soviet area of the Caspian Sea Pump fishing without electricity
became successful for small types of clupeid fishes.
37
The fish, a sardine-like species found by echo-sounder, are
attracted by light and pumped on board the vessel while the
suction nozzle, with two lamps of 1500 W, is moved up and down

Pump fishing became successful in the squid fishery. Off the Californian coast, squid
were attracted by light from an anchored vessel.
38
Pump fishing with light and
electricity.
Pump fishing with light for squid off the Californian
coast. (Courtesy Susumu Kato, National Marine Fisheries Service, La
Jolla, California.)

Hydraulic dredges with
pumps and/or conveyors
2

40
• This is a type of dredge with a net bag towed by a
motorboat equipped with a water pump.
• The supply pipe receives high-pressure water through a
hose from the pump on the boat. The water jet stirs up the
bottom sand together with the shrimp, which are trapped in
the bag of the dragged dredge.
• The shrimp are taken out of the gear by frequent hauling.
Hydraulic dredges with pumps
Fig. Hydraulic cockle dredger with
suction pump

41
• Some of the dredges are so improved that the prey is not only captured and collected in a bag,
but is also conveyed on board the vessel by the same gear. Therefore, this gear, combining
digging and hauling, can be considered a harvesting machine .
• This is especially true in cases where mechanical shellfish diggers are combined with suction
pumps, escalators or conveyors.
• In this type the dredge is combined with an air lift pump, lifting the mussels to the separator on
board, from where the clean washed cockles are delivered by a chute to the hold.
Fig. Mechanical dredger with pump

42
• The dredge is lowered from a small gallows and towed by a single
warp. Two pipes run to the dredge .
• The smaller one is a high-pressure PVC hose directing the water,
under pressure, into the large pipe by means of an internal jet.
• Suction is created in the larger pipe on the Venturi principle. It is
this suction which picks up water and cockles and forces them into
the boat.
Venturi principle

43
• Another way of bringing the washed-out shells on board the dredging vessel is to work with
‘mechanical escalator harvesters. In this case the shells are hauled with the help of a conveyor.
• A disadvantage of this system is that more sand is transported by the belt as compared with a suction
pump.
• The basic design of such elevator dredges invented and introduced about 1951.
Hydraulic dredges with conveyors
Fig. hydraulic dredges with conveyors

Amphibious mussel Harvester
44
• There are problems involved in shell dredging in tidal areas,
There it was necessary for boats to go to the fishing places or
mussel beds during high tide, work there during low water and
then wait for high tide again in order to return.
• The problem was solved with an ‘amphibious mussel
harvester’. This vehicle can be operated like a boat to reach
the fishing place, work there as a wheeled craft in the low
water, and drive back into deep water to return to port as boat.
Four and three-wheeled models are available.
amphibious mussel harvester
3-wheeled model
4-wheeled model

Harvesting machines
for aquatic weeds
3

46
 Aquatic plants in fresh waters and sea waters can be
harvested for commercial use and also as a form of
plant control. Traditionally simple gears like sickles,
scythes ,rakes and ranching gear are used for cutting
and collecting.
 Now adays some gears are so mechanized that it can
be called as harvesting machine because it not only cut
the seaweed under water, collect it, and lift it aboard,
but can also transport large quantities and discharge the
material on the shore. Some of these harvesting
machines can also chop, press and de-water the
material, so that a wet pulverized weed is the final
product.
 Most projected harvesters have been based on the idea
of a large flexible tube with a rotating cutter at one end,
the cut weed then being drawn up with a pump.
Figure. Russian crane with turning implement for
harvesting Laminaria.

47
Fig. French harvesting machine for algae ,laminaria
• The French operate a similar gear for harvesting Laminaria . There a small crane is mounted on the
vessel with a spiral for twisting together and tearing out the seaweed .
• The crane is also used to unload the harvested seaweed from the vessel onto a truck on shore. For
this purpose the crane is fitted with grabs.

48
Kelp harvesters are like giant seagoing
reaping machines or lawn-mowers . The
barge-like harvesting machines will be moved
back and forth over the designated harvesting
area. The kelp is cut by the large cutting racks
at the rear of the vessel and conveyor belts
haul the cut seaweed aboard.
Fig. kelp harvester in operation

Fully automatic
longline systems
4

Automated Long line systems
50
• In fully automatic longline systems every step in the shooting and hauling operation including
baiting and removal catch are automated .
• Automated long line system consists of a line hauler with a mechanized method of cleaning
the hooks and untangling branch lines from the main line.
• In some systems , the branch lines are separated and stored on racks or magazines and the
main line is wound and stored on a drum. In other systems mainline with branch lines are
stored on drums .while setting ,the hooks are baited by drawing through an automatic baiting
machine.

51
Typical layout of a Line hauler

52
• Fishing system and harvesting machine.ch 30, page no. 473-482 , fish catching methods of the
world.
• MFR Paper 1176. From Marine Fisheries Review. Vol. 38. No.2, February 1976.
• www.wikipedia.org
• Google images
References

Fishing systems and harvesting machines

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