Aquaculture techniques in other countries
Farms differ by place and species. Salmon are raised in large floating sea cages (Norway, Chile). Shrimp are grown in earthen ponds (Vietnam, India, Ecuador). Carp are grown in freshwater ponds, often with several species together (China, India). Oysters and seaweed grow on ropes in the sea and need no feed. Some farms use recirculating tanks (RAS) on land, where water is cleaned and reused.
The best farms copy ideas from each other: vaccines, better feed, water sensors and low-waste methods.
Keeping ornamental fish
Ornamental fish (goldfish, guppy, angelfish, koi) are kept for beauty and are also a business. Good keeping needs: a tank big enough (about 1 litre of water per 1 cm of fish as a rule of thumb), a filter, an air pump, the right temperature (about 24 to 28 degrees C for tropical fish), light for 8 to 10 hours, and small meals once or twice a day. Do not overfeed: extra food rots and poisons the water. A new fish goes into a separate tank for about two weeks (quarantine) so it does not bring disease. Never release aquarium fish into rivers: they can become invasive.
Aquaculture business management
A farm is a business. Costs: seed (fingerlings), feed, labour, energy, nets and equipment, and loan interest. Income: price times kilograms sold. Profit = income minus cost.
Management steps: choose a site and species; plan the cycle (stock, feed, check, harvest); keep records of feed, deaths and water; control crowding (stocking density); watch the market price; plan for risks such as disease, storms, red tide and price falls (insurance helps). Too many fish use up oxygen, grow slowly and fall sick, so more fish is not always more profit.
Aquaculture laws and rules
Countries have different laws, but the same aims. Typical rules:
- Licence or permit to farm, and rights to use the water or land (site approval).
- Environmental rules: limits on waste, chemicals and effluent; no clearing of mangroves; checks of effect on nature.
- Water and health rules: report disease; control the movement of live fish and seed; quarantine; limits on antibiotics.
- Food safety and tracing: records so that each batch can be traced; hygiene during harvest and sale.
- Species rules: protect wild species; permit needed to bring in non-native fish; ban on taking protected animals.
- Workers and safety: safe boats, fair work.
Breaking the rules can mean fines, closure and loss of market.
Try it
In the 3D free play, find the fish count that gives the highest profit (about 25 to 30 with medium feed). Then raise the fish count to the maximum: what happens to oxygen and profit? Write why in one line. At home: plan a pretend small farm with a list of costs and income.
Key formulas and definitions
- Profit = Income - Cost
- Income = price per kg x kg sold
- Stocking density = number of fish / volume (or area) of water
- Feed conversion ratio (FCR) = feed given (kg) / weight gained (kg)
- Survival (%) = fish alive at harvest / fish stocked x 100
Worked examples
1. A farm spends 40000 on seed, 90000 on feed and 20000 on other costs. It sells fish for 190000. Find the profit.
Cost = 40000 + 90000 + 20000 = 150000. Profit = 190000 - 150000 = 40000.
2. A pond gets 2000 fingerlings and 1700 are alive at harvest. Find the survival percent.
1700 / 2000 x 100 = 85 percent.
3. Feed given is 300 kg and fish gained 200 kg. Find the FCR. Is a lower FCR better?
FCR = 300 / 200 = 1.5. Yes, lower FCR means less feed needed per kg of fish, so lower cost.
Common mistakes
- Thinking more fish always means more money. Crowding lowers oxygen and growth.
- Overfeeding. Extra feed costs money and rots in the water.
- Forgetting records. Without records you cannot trace fish or prove the rules were followed.
- Releasing aquarium fish into a river or sea. They may harm local species.