Fish farming

Maintaining water quality

Maintaining water quality

1. tidal/flowing water

2. filter

3. allow water to drip through

4. aerator

Maintaining oxygen levels in ponds and tanks

1. agitated mechanically so air mixes with water (more oxygen dissolves in it.)

2. recirculated using a pump.

3. artificially oxygenated by bubbling oxygen through it.

Maintaining oxygen levels in open water (cages)

1. natural flow of water brings fresh oxygen to cages.

2. plants in the water (rooted plants and microscopic algae) emit oxygen during photosynthesis.

Interspecific predation

one species eating a different species

Intraspecific predation

one animal eating another of the same species

how do you control interspecific predation?

nets cover open pond to prevent predatory birds from catching fish.

how do you control intraspecific predation?

1. number of fish in one area kept fairly low.

2. provide adequate amounts of food.

How do you prevent disease in fish farms?

(in order to maintain good yield of fish)

1. chemicals added to water.

2. antibiotics in fish feed

3. low density of fish reduces spread of disease.

Eutrophication

• nitrogenous excretory products from fish accumulate in water.

• must prevent excess levels of waste becoming to high. Eutrophication can occur.

• Eutrophication - excess nutrients cause too many plants and algae to grow in the water.

• this reduces oxygen levels for the fish.

good quality diet for fish

• high protein

• fats, carbohydrates, vitamin and mineral ions.

• higher portions of protein are needed when the fish are younger because they are growing rapidly.

fish feed

• protein source for feed derived from smaller fish and waste from fish-processing industries.

• fish feed = pellets

How are the fish fed (manual)

fish farmers feed by hand. Ensures fish are healthy, with no issues.

How are the fish fed (computerized)

• sprays feed out of storage bin.

• shuts off automatically when infrared sensors below tank detect feed falling to bottom.

Explain how to improve the yield of fish

1. select superior individuals for breeding

2. obtain good stock from fish who supply eggs.

3. populations with fish that are all female or sterile give higher yields than mixed sex populations.