FISHERY
Fishery is a branch of agriculture that is involved in raising fish/fishes or other aquatic animals like sponges,
shrimp etc. All fish are vertebrates that live entirely in water.
CLASSIFICATION OF FISH
Classification of Fish based on their Habitat
Habitat is the place where organisms live. Fishes are classified into the following:
1. Freshwater fishes: Freshwater is a water body that has little or no salt in it; e.g. streams, ponds, springs, rivers, swamps and lakes. Fish/fishes that lives in freshwater are called freshwater fishes; e.g tilapia, mudfish, catfish. Freshwater fishes cannot survive in salt water.
Tilapia
Catfish
Mud fish
Salt water are also called brackish or marine water. . Saltwater is a water body that has high proportion of salt in them. Saltwater fishes are fishes that live in saltwater. Fishes that live in salt water include sharks, eels, mackerel etc.
Mackerel
Eel
Morphology is the study of structure of the body of organisms. Since most fishes have basically the same structure, we can classify them based on their skeleton or body frame thus:
Bony fish: They are fishes that has their skeletal axis made of hard bones e.g. cichlid or Tilapia, mudfish, carp, trout, cod (stockfish), eel, catfish, etc. Most of them are found in fresh water.
Trout
Cod (stockfish)
Cartilaginous ilsh: They are fishes that has their skeletal axis made of soft or catilaginous bones e.g. shark, dolphin, skate, ray, dogfish. Most are found in the sea or salt water, fig.8:4.
Other types of Aquatic Organisms
Shell fish or crustacean: they are aquatic organisms that have hard exoskeleton or outer skin with jointed legs. They do not have backbones (they are invertebrates) e.g. crab, shrimps, crayfish, prawn, lobsters, and oysters.
Molluscs: They are aquatic animals that have soft foot or body segments. They do not have backbones (they are invertebrates) e.g. snail, periwinkles, squid, octopus.
Amphibians: They are aquatic animals that crawl and have four limbs/legs; and can spend some part of their life on land and others in aquatic environment. They have backbones (they are vertebrates) e.g. frogs, toads, etc.
Reptile: They are aquatic animals that crawl and have four limbs/legs. They have backbones (they are vertebrates) e.g. turtle, crocodile.
5. Mammals: They are aquatic animals that breast-feed their young ones with milk from their mammary glands (breast). They have backbones (they are vertebrates) e.g. hippopotamus, whale.
Uses of Fish
1. Serves as food for fanner. It is eaten fried, boiled, stewed or roasted.
2. Source of revenue to farmer when sold in the market.
3. Used for beautification purposes in the form of pond, aquarium.
4. Serve as feed for. some farm animals or pet animals.
5. It generates foreign exchange to the nation when exported to other countries.
Uses of Fish Products
1. Fish bones are used for the manufacture of glues and fertilizers
2. Fish product like cod-liver oil is used for medicinal purposes to make capsule.
3. Fish are used in making fish meal to feed animals such as poultry chickens.
4. Scales are used by artist for decoration.
FISHING EQUIPMENT
Fishing equipment can be grouped according to the way they are used into the following:
L Nets: This is usually made with thread or nylon, with small weight attached to the edge of net to make them sink when placed in water.
Fig.8.5: Fishing Nets
Traps: These are cages made with wire and used in water bodies to catch fish and prevent them from escaping (fig.8.6). Baits (e.g. earthworm) may be used to attract fish to the trap.
Fig.8.6: Fishing Trap
3. Fishing pots and gourds: Equipment made with calabash to catch fish in small water bodies.
4. Basket: Deep and tapered to the base that are used in shallow water bodies to catch fish.
5. Equipment to wound: These are equipment used to kill or incapacitate the fish after catching or trapping to prevent them from escaping e.g. spears, arrows, knives, hooks etc.
FISHING METHODS
Fishing methods are the processes involved in catching fish. It varies according to the type and size of fish to be caught, culture and norms of the people, type of water body in that area. Fishing methods can be divided into two major groups:
1. Small scale fishing: This is practiced
locally in small fishing camps. They have the following characteristics:
a. Few fish are caught
b. Simple or crude equipment are used such as bamboo rafts.
c. Simple techniques are used.
d. It is carried out in small water bodies.
2. Large scale fishing: This is a complex fishing method that is carried out on large water bodies like oceans. It is expensive to operate. They have the following features:
a. Several fishes are caught.
b. More u advanced and complicated equipment are used, such as fishing trawlers.
c. Involves complex techniques.
d. It is carried out in large water bodies.
The methods used by fishermen to catch fish depend on the type of fish, the size of fish, and size of water body in which fishing is to be done. Different fishing methods include the following:
1. Using ocean going fishing trawlers (fig.8.9) to catch fish and shrimp.
2. Fishing with small boats using net along the coast.
3. Using fishing nets by casting them in trenches and canals.
4. Poisoning rivers, creeks, lakes and ponds with certain chemicals, leaves and roots.
5. Shooting, chopping and spearing with arrows, cutlasses and spears.
6. Use of explosives: This is done by detonating explosives like carbide inside water body to kill fish.
7. Use of electric stunning: This is done
by passing electricity through the water body to kill fish.
8. Draining water body: this will remove the medium on which fish can survive, thereby exposing them for harvesting.
9. Using fish baskets.
10. Using fish traps.
RISK FACTORS AND FISH FARMING
1. Poisoning method of fishing can contaminate fish, accumulate in it and eventually poison the consumer of the fish.
2. Using chemical for fishing can also pollute the water body, killing other aquatic organisms.
3. Use of electricity, will also electrocute other aquatic organisms.
4. Use of explosive also pollute the water body, destroy the habitat and kill other aquatic organisms.
PRESERVATION OF FISH
The major reason for processing and preservation of foods like fish is to reduce wastage by spoilage organisms and preserve their quality over a long period of time. This involves mostly removing the water content from the fish that encourage spoilage microorganisms. Excess fishes that are not eaten needs to be preserved. The process include the following:
- Salting/brining: Involves using common table salt to preserve fish. This is done by applying salt directly on the fish or soaking the fish in salty water for a long time. Salting prevents activities of spoilage organisms by removing water that is required for their activities to cause spoilage.
The fish are usually dried in the sun or oven after salting for longer preservation,
- Sun-drying: It helps to reduce the water content offish by spreading it in the sun.
- This is one of the oldest method. It is done by using simple oven of mud on a charcoal or wood fire over a wire guaze. Before smoking, intestine are removed and the fish positioned in the oven.
Roasting: Involve placing fish directly on fire. It preserves fish for few days.
Freezing: Freezing involves keeping the fish at temperatures below 0°C or at freezing point.
- Canning: Involves enclosing fish in airtight container with special oil to preserve them. Examples of canned fish are sardines and mackerel.
- Frying: Involves frying fish in either their oil or other oil.
Advantages of Fish Preservation
i. Improve the taste and flavour offish, ii. Extend the time the fish can be used, iii. Retain the quality of the fish, iv. It reduces waste.
v. It aids distribution to consumers after packaging of processed food.
Disadvantages of Fish Preservation
i. May lead to weight loss offish, ii. May be contaminated with soil or dust, iii. Spoilage may start from inside the fish. iv. In case of freezing, power failure can
lead to spoilage offish. v. Require technical expertise/knowledge.
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