KEAM Fisheries: Aquaculture, Water Quality and Fish Biology
What this domain tests
Fisheries in KEAM uses the PCB stream and covers fish biology, aquaculture, capture fisheries, water quality, nutrition, breeding and fish health. Questions apply biology and chemistry to pond and coastal management.
Core rules and concepts
- Water quality: dissolved oxygen, pH, temperature, ammonia and alkalinity determine carrying capacity; unionised ammonia is toxic and rises with high pH and temperature.
- Stocking: density is fish per unit volume or area; biomass is density × average weight.
- Nutrition: feed conversion ratio = feed offered ÷ weight gain; lower FCR is better.
- Breeding: inducement, hatchery management and larval rearing; monosex culture controls unwanted reproduction.
- Health: biosecurity, quarantine and disease surveillance reduce losses.
Worked example
A pond is 50 m × 20 m × 1.5 m deep. Volume = 50 × 20 × 1.5 = 1,500 m³. At a stocking density of 5 fish/m³, stock 1,500 × 5 = 7,500 fish. If the pond were treated as 1,000 m³ by using a 1 m depth, the estimate would be 5,000 fish and feed calculations would be short. The reasoning is to multiply all three dimensions before applying a volumetric density.
Traps that cost marks
Using surface area when the question gives stocking per cubic metre; confusing ppm with percent (1 ppm ≈ 1 mg/L in water); calculating FCR with wet feed and dry gain without noting the basis; and ignoring that ammonia toxicity depends on pH and temperature, not concentration alone.