All the activities relating to the production of fish and other aquatic animals known as fisheries. Fishes are cold-blooded animals, that is their body temperature changes according to that of their surroundings in which they live. They breathe with the help of gills and swim with their fins. They feed on plankton. All fishes are vertebrates, that is, they have backbones and scales. They have steam-line body for swimming freely in water. fish may be viviparous, oviparous, and ovoviviparous in reproduction.
Fishery is the area of specialization in agriculture that is concerned with the production of fishes as well as other aquatic animals. The rearing of fishes (fingerlings) or fryers in ponds or other enclosed bodies of water until they reach table size is called fish farming. A person who sells fish is referred to as monger.
Classification of Fishes
Fish can be classified according to their:
Classification of fish based on habitat
On the basis of habitat, fish can be classified into:
- Fresh water fish.
- Salt water fish.
- Estuarine fish.
- Fresh water fish: These are fishes that are capable of living and reproducing in waters free of salts. Such waters include artificial or natural inland ponds, lakes, swamps, rivers and streams. Examples of fishes here are tilapia, crayfish, carp, catfish, common eel, nile perch etc.
- Salt water fish: These are fishes that do not well only in salt water. Such waters include coastal lagoons, sea and ocean. Examples of fishes are herring, crabs, lobsters, sardine, cod (stock fish), shark, mackerel, croaker, sole and ray.
- Estuarine habitat: This means water found in estuaries where rivers flow into the sea or oceans. Example is the Niger Delta area of Nigeria. The salt content of this habitat is in-between the content of marine habitat and fresh water habitat.
Fishes may not permanently live in this kind of habitat as some do move from fresh water or from salt water into the estuaries and return thereafter. A typical example of such fishes is the mudfish.
Classification of fish based on morphology
Fishes can also be classified on the basis of morphology, that is, structure of their body. There are two types of fishes according to their morphology. These include.
- Bony fish
- Cartilaginous fish
- Bony fish: In bony fish, the body frame (skeleton) is made of true bone. The body is covered with spindle-shape scales. The gill slits of bony fish are covered by an operculum. Examples of bony fishes are catfish, croakers, mackerel, tilapia, claries and perch. In Nigeria, most of our fishes fall within the fresh water and bony groups.
- Cartilaginous fish: In cartilaginous fish, the internal skeleton is mainly cartilage rather than bone. Cartilage is a substance like bone which is firm, shiny and elastic. The skin is tough which is covered with small scales.
The pelvic fins of male have a copulation organ known as claspers. Cartilaginous fish have about five to seven gill slits that are open to their external environment.
Examples of cartilaginous fish found in salt water habitat are dogfish, sharks, rays, electric eels and saw fish.
Other types of aquatic organisms
Although fishes are the most common aquatic animals which we eat, many other aquatic animals are also caught by fishermen and consumed by man or used for many other purposes.
The other large aquatic food organism can be classified into two major groups:
Vertebrates: Aquatic vertebrates can be classified into two major groups
- Amphibians e.g. toad and frog.
- Reptiles e.g. turtle, crocodile, river snake, alligator.
- Mammals e.g. whale, dolphin, hippopotamus.
Invertebrates: These consist mainly of animals closely related to spiders, scorpions and insects. They are called crustaceans.
Examples are crabs, shrimps, lobsters, prawns and the snails and their relatives e.g. periwinkles and oysters which are also examples of invertebrates.
Uses of fish and fish products
- Fish skins are used as leather for making shoes, bags and other leather works.
- Fishing is a hobby to some people, and a source of employment.
- Fish can be raised for sporting purposes.
- Fish serves as a source of financial reward to farmers.
- It is a source of foreign exchange.
- Fish is used as food which serves as a source of protein, vitamin (A & B) and minerals.
- Fish is used as food which serves as a source of protein, discards are used as industrial raw materials.
- Fish can also serves as feed to livestock e.g. fish meal.
- Fish oil is a very rich source of vitamin B and D and as such fish is processed to extract the oil for use in curing vitamin deficiency as in the case of cod liver oil.
- Fish can serve as pets in the house aquaria. Here, beautiful coloured fishes are used.
Fishing methods and equipment
There are various fish habitats e.g. swamp, rivers, coastal lagoons, ponds, streams, seas and oceans. As a result of this, various methods are employed to catch fish. Example is coastal and deep seas and oceans referred to as distant fishing system. Here fishes are caught with the help of a bag-shaped net called trawl, which is fixed on boats and ships called trawlers.
In the case of inland water fishing, i.e. fishing in ponds, streams and rivers or swamps, simple methods and equipment like fishing line and hook, harpoons and spears, traps and nets are used.
Fishing equipment/kinds of fishing tools
There are different kinds of fishing equipment commonly used in Nigeria. They can be grouped into four types
- Wounding equipment.
- Netting equipment.
- Trapping equipment.
- Fishing without equipment.
- Modem equipment.
This is a fishing gear that can be used to wound the fish as are being caught. They are very useful for killing fish, struggle as they are being caught. The fish cannot escape when wounded. Examples of wounding gears are knives, arrows, hook and line.
Spears, harpoons, and knives: These are used to pierce or cut fish in the water to wound and kill them. (Impaling)
Hook and line: Using hook to fish is a very common method used by young people. The hook is attached to a nylon or cotton rope called the line which is tied to a short length of bamboo or stick. Bait which may be an earthworm, insect larva and sometimes a small fish is attached to the hook. When a fish tries to feed in the bait it swallows the hook, the floater shakes in the water and the fisherman knows immediately that his hook has caught a fish. In some cases many hooks are attached to a long line, which is left in the water to catch several fish at the same time.
There are different types of fishing nets (netting equipment).
Gill net: This net is in the form of a contain of net suspended vertically in the water. The net is normally made of nylon twine. Floats are fixed to the top of the net and sinkers attached to the bottom which keep it in position. Thus, any fish which try to swim through it is trapped in the meshed. Until the fisherman can raise them.
Drag net: This is made up of a thick rope running round the top mesh of the mouth and has a cork floats on the surface with heavy pierces of lead at the bottom. The use of this net involves about four fishermen or more to be result oriented. It is set in water in a semi-circular form and dragged to the ground to facilitate the removal of the fish.
Cast or throw net: This is a conical shaped net with lead weights fixed along the edge of the open end. It is between 4-7 meters in length and a line of about 4-10 metres used in retrieving the net. (pill it in). When a fish is sighted, it is thrown into the water. It sinks and later encloses the fish the fish trapped inside its use requires a boat and great skill in casting.
Seine net: This is non-selective in cropping of fish, and it is used to harvest both young and mature fish because it has a small mesh. It has lead sinkers and floats which are fixed to the top ropes thereby forming an enclosure where fish is trapped and unable to escape.
These are used along riverbanks, streams and swamps. Examples of fish traps are:
- Funnel entrance traps: Fishes swim into the unbaited traps and are unable to escape.
- Triggered traps: These are usually baited with some foods e.g. Guinea corn meal, fish piece or snails. As fish approach the baits, they set off the trigger which causes the door of the trap to close behind the fish. They are designed with bird cages.
Fishing without equipment
- Fences: The fences are made from bamboo, wood or raffia palms, which are placed across shallow streams or rivers. As water flows, fishes are trapped behind the flow where they are periodically collected. Fences are commonly used in swampy areas where there is a flood plain. They are usually erected across the connecting channel between swamp and the river at the time the flood is receding. In effect, fish that are stranded due to low water level are caught.
- Draining of ponds: This entails the removal of all water in the pond in order to harvest the fishes. Hand or scoop net is used for scooping out fish from the drained ponds.
1. Trawlers: This has a bag-shaped net called trawl. This is used in commercial farming by big fishing companies. They are attached to ships and drawn into deep sea. It catches fish of very large sizes, and also has units for preserving such fishes caught. The bottom of the trawler is installed with a propeller which it uses in cutting fishes. It is usually non-selective in harvesting.
2. Ultrasonic: This is a noise-making device which attracts or lures fishes to a particular corner of the pond before the fisherman can then catch them.
3. Electro-Fishing: This is a non-selective method of harvesting. A current of electricity is passed through the pond creating an electric field in an enclosed area and later all the fishes are shocked and killed.
Risk factors in water and fish farming
- Polluting water with chemicals / industrial effluents or waste.
- Contaminating fish with chemicals used for catching fish
- Natural flooding.
- Disease out-break.
- Very low and very high Ph level of water.
Factors affecting siting of a fish pond
Soil type: Clay soil is most suitable for siting a fish pond. Sandy soil and graveling land should be avoided as they encourage seepage.
Water supply: It requires a constant source of water supply, which must be of good quality. The pond water should be free from industrial waste e.g. salt and other pollutants.
Topography: A gentle slope or flat land is ideal for fish pond construction. Low land should be avoided as it encourages flooding.
Availability of market: The fish pond should be sited in areas where harvested fishes can be easily marketed. For example, marketing of fishes is easy and quick in the south-south zone of Nigeria.
Availability of labour: This means that the services of both skilled and unskilled workers should be readily available in areas where fish ponds are to be side.
Availability of baby fish (fish seeds): Fish seeds, that is, small fishes should be easily obtained when fish ponds are to be established.
Availability of feeds: Fish supplements such as groundnut cake, palm kernel cake, poultry droppings, etc should be easily reached.
Vegetation: Thick vegetation should not be used so as to reduce the cost of clearing and stumping.