Fishing and harvesting methods in Reservoirs

M. Feroz Khan and Preetha Panikkar

Reservoir Division of Central Inland Fisheries Research InstituteHessarghatta lake Post, Bangalore-560 089

Reservoirs are considered to be the most unexploited water resources in the country while the production potential from this ecosystem is enormous. These waters harbour a wealth of fish fauna and the success of fisheries in a country depends on optimum harvest of its fish fauna, for which use of appropriate crafts and gears is essential. Reservoirs pose many hazards for large scale fishing operations. Tree stumps, boulders and other submerged obstacles cause considerable damage to the fishing gear. . Suitable gears for successful exploitation of the fishing of reservoirs are limited

In India, a large variety of crafts (boats) have been designed for Inland fishing. The nets or gears and other devices for catching fishes are also numerous and ingenious. But both crafts and gears were invented centuries ago and probably have remained static and have shown little or no change or improvement in India, unlike in other countries. This has hindered or restricted the exploitation of our inland waters. It is only in the last decade or two of 20th century that some attempts have been made to use motorboats and modern steam vessels for the purpose. For the efficient management of fishing, it is imperative to know the type of fishing crafts and gears used in reservoirs

A. Fishing crafts

Fishing crafts are most essential for catching the fish in large scale water bodies. Even these crafts are essential when the fishing grounds are far from the coast. Before the advent of mechanisation of fishing crafts, man living on the shores of oceans and banks of estuaries, was nourished by the fish that could be captured by using whatever the craft that he would use. In most countries usually indigenous, non-mechanised and locally built fish crafts are in vogue. These crafts have been design to suit the local conditions.. The types of fishing crafts of India falls under two general categories. These are non-mechanised and mechanised fishing crafts. The categories of fishing craft types comes under non machanised are, dugout-canoes, plant built canoes, masula boat, built up boats. The mechanized crafts are line boats, trap boats, dolnetter, gill-netter, trawlers. Some of the different kinds of fishing crafts used for fishing are discussed below.

Dugout canoes

The dugout canoes are made from the hollowed trunk of a tree. They are used for fishing in reservoirs in many parts of the country. There are 10-20 m long boats, which can be operated by one or two fishermen. They can also be

used for fishing in rivers and canals. The small dugout canoes are known as Dhonies

Plank-built canoes:

This is an enlarged variety of dugout canoe made of planks on the sides, largely used in localities such as Kerala.

Masula boats:

It is made of non-rigid planks sewn together with coir ropes as the ones along Andhra coast.

Dinghy:

This is a carvel type of boat designed and constructed for a variety of purposes including fishing.

Built-up boats:

In most of the boats made at present, the carvel type of boats is built up of planks. The best type of built-up boats is seen in centers along the northeast coast of India.

Dol netter:

The dol netters are used for operating the dol nets, which are basically fixed bag nets. The dol netter varies form 8-14mm length, 1.5m to 3.6m in breadth and 0.8m to 1.8m in height. The carrying capacity of each of such boats varies from 2-14 tonnes. Each of these boats is fitted with 2-4 cylinder diesel engines.

Coracle

A coracle is a saucer shaped bamboo craft with a round basin, constructed with split bamboo, the outer surface covered with leather. Since the leather and its maintenance are costly, fishermen in recent times resorted to the low cost coracle. The frame is constructed with split bamboo and the outer portion is covered with synthetic fibre cloth with bitumen coating over it. It is widely used in rivers, reservoirs and tanks in Southern States of Kerala, Tamil Nadu, Andhra Pradesh and Karnataka.

Kakinada Nava

It is a keel-less boat of about 9.5 m length; made of teak wood and carved built. They are constructed with frames and ribs. It is of the open type with little space decked. They are used in lakes and reservoirs.

Theppam (Thermocol Raft)

It is confined to the state of Andhra Pradesh . It is the most rudimentary craft used by traditional fishermen in the state. It is a keel-less craft formed by lashing together 1 or 2 pieces of light thermocole. There is no definite length or width. Only one person can operate the gill net with the craft.

B. FISHING GEAR

The word ‘fishing gear’ is synonymous for ‘fishing net’ which is used to catch the fish in the water bodies. Generally the fishing gears are categorized as active and passive gears. The passive gear needs knowledge of behavioral biology of the fish to be caught, as the fish has to enter the stationery gear voluntarily. In the case of active gears, they are operated (either towed by boat or moved by hand) in the path of the fish concentration and general energy intensive, more productive than the passive gear. Fishing gears are also referred as drift nets or set nets depending on whether the nets are moved in water or made to remain stationary in water. Normally selection of a particular fishing gear (whether active or passive gear) is done according to the type of species caught in the fishing grounds.

Types of Fishing gear:

Basing upon the usage of materials and construction, the fishing gear is catagorized into 1. Net fishing gear, where fishing gears are predominantly constructed of netting eg. Gill net, seines, trawls: 2. Tackles in which hooks are an important part and 3. Miscellaneous gear covering all the other gears such as traps, wounding gear etc. The following are the various types of fishing gear presently in operation in Indian waters

Gill net.

Gill nets are used world wide in order to catch every kind of fish, because the structure of the gear is very simple and one of the cheapest fishing gear. A gill net is a net wall where lower end is held in vertical position in water column by weighted sinkers and the upper end is held at the water surface by floats. When fish shoals are confronted by the presence of a gill net, frightened fishes attempt to pass through this net wall and during this process the fish get caught at their head portion. Gill net happens to be one of the most prominent fishing

gears presently used in fishery sector. Gill nets are operated as both drift nets or bottom-set nets.

Structure of simple gill net

A simple gill net consists of the float line, lead line, gavel lines (side ropes), floats, sinkers, buoys and buoy lines. The netting is mounted to the float line and the lead line according to a particular hanging ratio. Hanging coefficient determines the mesh shape and hung depth of the mounted gill net. A few meshes along the upper, lower and side edges of the main netting are generally strengthened either by using thicker twine size or by using double twine in order to protect the webbing from damage during handling and operation. A number of gill net units are attached end to end to form a fleet of nets.

Classification of gill nets

Depending on the type of fish to be caught and the fishing graved conditions; the gill nets are broadly classified into 3 basic types. They are (a). Fixed gill net (b) Drift gill net and (c) Encircling gill net. Actually there are six types of nets in use in gill net fishery. Between these two nets, have been proved as the best catching capabilities. (Fixed bottom gill net and drift gill net for surface and middle-depth fishing). Drift/surface gill net used to catch the fish, which swim near the surface water. Either one end (or) both ends of the nets are fixed to the bottom to prevent the net from drifting away by the current (or) winds while in operation. This type of gill net does not require any anchor and is most suitable for the pelagic fishery in large scale. Bottom gill net is fixed on the bottom with anchor to catch bottom dwellers. The total sinking power of the net, ropes and sinker is large than the buoyancy of float.

Set gill nets or anchored gill nets are fixed to the bottom or at a distance above the bottom by means of floatation and ballast. In shallow waters they are fixed by means of stakes driven to the ground. Encircling gill net is operated for catching fish shoals feeding or moving in the surface layers. It is operated in the shallow waters and the lead line usually touches the bottom. After encircling the shoal, sound and vibrations are used to drive the fish towards the net so that they are either gilled or entangled.

Based on structure and method of capture, gill nets are grouped in to simple gill nets; trammel nets and combination gill net-trammel net. Simple gill net consists of a single wall of netting supported by floats and sinkers. The mechanism of capture is by gilling. The meshes in gill nets are large enough to allow a fish’s head but not the rest of the body to pass through. When the fish tries to back out of the net it gets caught behind the gill covers. Trammel nets are generally triple-walled with a loosely hung small-meshed panel between two large meshed panels, which are relatively tightly hung. The inner wall intercepting a fish passing through the large mesh on the other wall forms a pouch after passing through the large mesh on the opposite side in which the fish is trapped.

Trammel nets are usually operated as bottom set. Some trammel nets consists of only two walls of netting. Entangling nets are loosely hung single or multi-walled netting of small meshes supported by floats and sinkers. The mechanism of capture is predominantly by entangling rather than gilling. The protuberances and spines on the body of the target species hold the fish.

Bottom set gillnet (Uduvalai)

Bottom set gillnets of 37 and 50 mm mesh bar with lengths of 60 to 90 m and widths 0.05 m to 0.75 m. are used. These nets are fixed at the bottom or at a certain distance above it by means of anchors sufficiently heavy to neutralize the buoyancy of the floats. These nets are efficient and generally operated in creeks and bays of South Indian reservoirs especially by Mettur fishermen and Killekethas in Mysore reservoirs.

Pedda-Uduvala

This is a modified bottom gill net possessing advantages of both the Rangoon and Uduvala nets, as these nets are wider (about 1.5 to 1.75 m) which increases the surface area. They are operated in deep areas of the reservoirs

Trawls

The trawl gear is a bag shaped gear dragged with in the water with the help of a towing boat. Its mouth is kept open by otter-boards and towed on seabed or at the desired water depth. Generally the trawl gear has larger size of the mesh at its towing end and the mesh size reduces gradually towards the cod end. The larger size of the mesh at its towing end is for the screening of unwanted fish species of certain size and the smaller mesh size at the cod end for retaining shrimp varieties. As such, the mesh size of the cod end webbing influences largely the size of fish caught by the trawl net.

Structure of a simple trawl: All trawls, whether small are large for both bottom and mid water trawling are basically funnel shaped with extending sides in the front to form wings which will prevent the fish from escaping when the trawl is approach. The trawl body is divided into cod end, extension piece, belly, baiting (top belly) square, lower wings, top wings, and flapper and chaffing gear. The trawls generally have a top canopy called the square extending forward from the top belly to prevent the fish from escaping over the top of the net. Panel sections are generally tailored from machine-made webbing. Top and bottom panels are attached to the head rope (head line) and the foot rope (ground line), respectively. Flapper is a suitably shaped piece of netting of smaller mesh size fitted in front of codend in such a way as to prevent the escape of fishes that has entered the codend. Most commonly used buoyancy elements are spherical floats, which are attached along the head rope. Floats along the head rope and weighted footrope keep the net mouth vertically open during operations. Rigid

kites or flexible sheers devices are also used to maintain the vertical opening of the trawl mouth. Trawl mouth is kept horizontally open using rigid sheer devices known as otter boards (trawl doors), which are attached to the wings either directly or by bridles or sweeps. Chaffing gear is some times provided underneath the codend of trawls operated in rough grounds in order to protect the codend from abrasion.

Trawler requirements: Generally 2 basic requirements are common to all trawlers. One is the need for “towing power” and the other is the need for a “winch” (or) “mechanically hauling system”. In order to have a good towing power, a trawler should have a reasonable draft (or) displacement and should have a large slow-turning propeller.

Types trawlers: The main types of trawl vessels are:

a. Otter trawlers (i) Side trawlers (ii) Stern trawlers (iii) Double rig trawlers

b. Pair trawlers (i) Bull trawlers/Bottom pair trawler (ii) Pair seines (iii) Cod pair trawlers (iv) Mid water pair trawlers.

c. Beam trawlers (i) Single rig (ii) Double rig (iii) Scallop dredgers (iv) Danish seiners

Bottom trawling is found to be an effective method for catching catfishes such as Aorichthys aor, A. seenghala and Wallago attu and other uneconomic fishes like Rohtee cotio. However, trawling need not be considered as a commercial method, but as a fishing technique to exert extra fishing pressure to control catfishes and other undesirable fishes in the reservoir.

Line fishing

Lines are widely used in both traditional and modern fisheries. The basic principle in this method is based on the feeding and hunting behavior of target species. Line fishing is an age-old fishing method practiced in India. This type of fishing is carried out, in India, mostly from the small traditional boats in the near shore waters. Line fishing is basically composed of a line and a hook. Hooks are made up of galvanized (or) aluminum coated iron, brass (or) stainless steel, with different shapes and sizes. A simple hook generally consists of a head (by which it is connected to the line), shank, bend, point and barbs.Other gear types

Similar to hand lining, traps and pots are used in rocky areas for capturing Lobster, Crab and other rocky fishes. Scoop net, bag net, stake net, cast net etc., are used in the estuaries and back waters. Some of these are very primitive fishing methods still used by the fishermen on countryside. Shore seines in near shore waters catch sometime fishes. Dole nets are traditional gear resembling

trawl net, but are held on with its mouth wide open with the help of two wooden posts driven deep. Hilsa and Bombay duck is the major share in the landings of dole net operation in the States Gujarat and Maharashtra respectively.

Cast net

It is a circular net, cast from the edges of the water or from the boat or a coracle and catches the fish by falling and closing it on them. Their use is restricted to shallow waters. It is made of a circular piece of net webbing. The circumference is inwardly curved, when it opens it forms a circular sheet, which imprisons the fish. The net is bordered with sinkers made out of leads. The net is throws over water and is held by a rope to its centre. The net spread like an umbrella over the group of fish. The sinkers provided along the perimeter facilitate sinking towards the bottom. When the perimeter touches the bottom, hauling line is pulled to raise the net on board and then the fishes are collected.

Potha valai:

This net is similar to the cast net in design, but it has no sinkers. It is spread in the river, embedded with some quantity or river sediment and the net ropes are attached to a stick in such a way that by pulling the main rope from a distance, the whole net will be lifted trapping the fishes therein. To attract the fishes towards the center of the net, feed balls made out of fried and powered millets with cow-dung are placed at the center of the net.

Shore Seine (Alivi)

It is large net for active fishing. It encircles a large part of water behind to contain a lot of fish. It is generally rectangular in shape and is mounted between a wire provided with leads. The net is kept stretched out vertically in the water and is operated from the shore. The net is kept in position by wooden floats 70-75 in number tied to the head rope at intervals of 1 to 2 m. One end of the net is left on the shore and other half gradually carries the rest of the net and places it in a semicircular way. Finally the two ends are slowly dragged by group of fishermen. The net is effective for medium and small fishes. Shore seine locally called alivivala is widely used in some south Indian reservoirs.

Kondavala

This is another miniature’Alivi’ in shape and appearance. The total length is 20 to 25 m, width from 20.5 to 3.0 m in the center, tapering on two edges to 1 to 1.5 m. Cotton twine is used in alivi and meshes are uniformly 10 mm bar throughout. Bamboo sticks of 0.75 m are tied at intervals making several pouches in the net during operation.

Dragnets:

Ari valai or Othukku valai are the two commonly used dragnets in Cauvery river. The mesh size of these nets varies from 25 to 35 mm and 5 to 10 persons normally operate the net.

Encircling net:

Thoorimal is a net of 6 to 10 m long used for encircling the bushes and macro vegetation for catching fishes.

Bag net:

This known as Tokavala. Large number of bag net units was found across the river in the estuaries of Vasista and Gautami exploring prawns and fishes. Fishermen push the gear through water and the gear scrapes the bottom during the operation.

Stow nets

Stow nets have a long bag, tapering into cod end. The mesh size increased from cod end towards the mouth, which is kept open by bamboo poles or anchors. The poles are driven to the bed of estuary and the net is fixed to the pole in such a way that the footrope is pushed into the mud and the head rope is in the level of the water surface. It should be hauled before the change of the tide. The catches are mainly sciaenids, gobies, polynemids, shrimps etc.

Falling nets

The gears are cast on the fish and the fish caught are retrieved through opening above, are called the plunge baskets. It is constructed out of bamboo strips having an opening at the top and is secured by coir at top.

Traps

These are indigenous devices prepared by fishermen for catching various species of fishes and prawns based on their habits and swimming behavior.

Screen barriers

Split bamboo laced together with coir rope arranged in transverse rows (thatties). Such screens are arranged as a vertical wall of screening and set in circular or rectangular shaped fashion and each end is curved inwards and brought close together leaving only a narrow passage leading into the chamber in between, which forms a trap.

Harvesting methods.

The way in which the principles of catch and strategies with both the gear features and its techniques with a set of conditions for a set of purpose of catch is a “fishing method”. The general design of the gear and the combination of principles of catch decide about the ‘kind’ of fishing method. The way in which the chief constructional features realise the purpose of the catch decided the ‘type’ of fishing method. The method of fishing or capturing the fish resources largely depends upon the habit and habitat of the species, constituting the resources. Numerous fishing methods operating today are based on a few basic principles. The methods include both frightening and enticing fish. When frightened, fish naturally disperse and as such this method cannot be used for any length of time. The method of enticing, is found to be effective to gather the fish and is therefore consider as an effective method.

A wide array of harvesting methods is used in fishery sector ranging from the most primitive to highly sophisticated methods. Some other methods such as fishing with out gear, in which the fish has been collected by bare hand or by foot; wounding gear where harpoon, spear, arrows were used to catch the fish by wounding and killing stupefying method, in which poison or under water explosives were used to paralyzed the fish and electrical fishing where application of pulsatile electric field is used to catch the fish.

Gill net operations

Gill nets are operated from a wide range of vessel classes ranging from small traditional crafts to large vessels of 50 m OAL and above. Gill nets and trammel nets are set across the current or the path of fish migration. The gear is set over the stern or over the side. The buoys and sinkers are thrown overboard manually to either side of the net to prevent tangling. Set gill nets are weighed with anchor and marked with buoys and flagpoles. In large-scale drift gill netting operating great lengths of nets, flagpoles and marker buoys are attached at intervals. Length of buoy lines in drift nets are adjusted so that the nets occupy the desired depth corresponding to the swimming layer of the target fish. Soaking time for drift gill netting is generally 4 - 5 hours. Bottom set nets are often set to soak over night.

Types of line fishing methods:

Handlining

Fishing in the shallow rocky areas using conventional gill nets and trawl nets is very risky and may damage the fishing gear. As such, fishes, which inhabit in hiding places like fissured rocks, crevices and on rough ground are generally caught with hand lines attached with hooks. Because of its operational

simplicity, small time artisan fishermen find it profitable to practice handling fishing in such areas. Moreover, it is a low energy fishing technique requiring minimum investment. Normally, each handling consists of a main line made up of nylon monofilament attached with a sinker and a branch line.

Electro-fishing (Electrical fishing)

Electric current as employed in fishing is harmless for fish; it does not affect the growth, the viability and the reproductive capacity of the fish. Also, the electric field created in water during fishing does not influence the food of the fish. On the other hand, electric fishing saves time, labor, money and manpower. At present, the electric fishing is being successfully used in several countries and on commercial scale both for river fishing and sea fishing. In electrical fishing an electric field is produced in water between two electrodes: anode and cathode. Electrical fishing operates on the principle of concentrating fish in a limited area between the electrodes, under the influence of an electric field, and then collecting fish by netting or fish pumping. Concentrating fish under electric field is based on behavioral reaction of fish to a certain electric current in fresh- or salt-water.

Commercial fishing in storage reservoirs of India pose lot of problems like submerged trees, rocks and boulders. These constraints impose restrictions on the use of wide variety of gear to exploit the fishery wealth of the reservoirs. Due to this problems large water sheets where there is rich fish population remain inoperable. In such waters, electrical fishing can be conducted. The experiments carried out with electrical fishing in Mettur, and KRS have shown that good result could be obtained in rocky and obstructed places. Specimens of Cirrhinus cirrhosa, C. reba, C. mrigala, Puntius dubius, P. carnaticus, etc. were found to be influenced by electrical current.

Light fishing

Side by side with electrical fishing, underwater light fishing has been conducted (lamp with different colours and illuminations) satisfactory results were obtained. Species like Cirrhinus reba, C. cirrhosa, Barbus mahicola, Anquilla sp., Mastocembelus armatus etc. reacted positively to the light.

Crow bow

The local fishermen commonly call it thettali. The gear is very rarely used as fishing device now days.

Explosives

Explosives (thotta) used affect all the living organisms in a large area. The dead organisms float to the water surface, which are then collected by using small scoop nets (prohibited).

Poisoning

It is commonly seen in the upstream part of the river. As a result of this practice, the affected species come out in an unconscious stage and then collected. Kudapana kaya and copper sulphate are generally used as poisoning materials (prohibited).

Fish Aggregating Devices:

Submerged bundles of twigs or branches of trees make attractive hiding places for fishes. The fishermen can catch the aggregated fishes easily by using small scoop nets. Generally, cashew nut tree branches are used for this purpose. This method is practised in certain down streams areas of the rivers and backwaters.

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