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Aquaculture: Cage Culture

A new type of farming in Indiana is gaining in popularity. This farming uses water rather than water. Aquaculture, or fish farming, is the practice of raising or harvesting fish (or other aquatic life) in a controlled environment.

There are four culture systems where you can raise fish:

  • Ponds
  • Raceways
  • Recycling Systems
  • Cages

Cage culture is a popular form of aquaculture that has many advantages that include resource flexibility, low cost, and simplified harvesting. This article focuses on cage culture.

Before investing any capital in a new business venture, it’s always good practice to do a thorough market analysis and develop a business plan. This will help you determine the size of the market, competition, and capital requirements. Markets are scalable from home consumption, to retail, to wholesale distribution.

Site Selection

After determining aquaculture farming is a viable interest for you to pursue, then the next step is to locate a body of water that will meet the biological and ecological requirements of cage culture. Lakes and quarries are possible sites. Some requirements to consider:

  • Size of body of water – at least 1/2 acre, but preferably an acre of larger
  • Water depth – at least 6 feet deep
  • Water quality – determine pollution sources and surrounding topology
  • Access to electricity – for aeration or other needs
  • Access to site – by boat or vehicle

Species Selection

Consider the marketability of your product and your grow out site. In Indiana, tilapia is a popular fish because of its large size, rapid growth, and hardiness. Hybrid striped bass, catfish, rainbow trout, and largemouth bass are other candidates for cage culture.

Hatcheries / Fingerlings

Once you have selected your species (or species), you need to find a hatchery that can reliably provide high quality fingerlings at a fair price.

For a list of commercial suppliers, see the Indiana Dept. of Natural Resources website:

Cages

Cage size determined the number of fingerlings to purchase. You want 5 to 7 fingerlings per cubic foot. Cages come in all size, but the minimum depth should be 4 feet. Cages can be purchased or homemade. Cages range in cost from $150 to $500 per cage. The size of your fingerling will determine the mesh size you need.

Make sure you leave at least 10 feet between cages when you add them to your site. Cages must be in quiet areas (away from swimmers) and easily accessible.

Water Quality

The water for your cage system must contain adequate oxygen to support the fish you are growing. Natural water oxygen can be supplemented with aeration. The dissolved oxygen level and temperature of the site should be monitored closely.

Fish Handling

Fish are shy animals and are easily subject to stress. You need to avoid stressing your fish to optimize their growth. Transport your fingerlings in a well oxygenated container.

Feeding

Fish grown in cages rarely obtain enough natural food and are therefore dependent on feeds supplied by the farmers. Floating feed is the preferred feed type and hand feeding is best. Feeding the fish with the proper amount is key for optimal growth, water quality maintenance, and operational expenses.

Fish Health / Husbandry

Vigilant observation and proper fish handling techniques to reduce stress, help maintain culture conditions. Biofouling is a potential problem that can be prevented by proper maintenance. Diseases may occur from time to time. Evidence of fish disease includes skin discoloration, open wounds and lesion, fin erosions, spots, and
erratic behaviour. Seek a disease diagnosis from an accredited lab and follow the recommended prevention methods.

Harvesting

Fish should be harvested as soon as they reach marketable size. Make sure you minimize stress during harvesting and maintain fish in well aerated transport.

References:

Continue your education by seeking out additional literature and by consulting with extension agents and other aquafarmers

Environment Conditions for Raising Tilapia

Tilapia are able to withstand a wide range of environmental conditions, including high salinity, high temperatures, high ammonia concentrations, and low oxygen levels. This makes tilapia very suitable for aquafarming.

Salinity

Although tilapia are freshwater fish, they can grow in elevated salinity conditions.

Fish
Salinity Tolerance for Growth
Nile Tilapia Grows well at salinities up to 15 ppt
Blue Tilapia Grows well at salinities up to 20 ppt
Mozambique Tilapia Grows well at salinities approaching seawater

Tilapia spawning is best in lower salinities. The fry perform better at salinities
less than 5 ppt.

Fish
Salinity Tolerance for Reproduction
Nile Tilapia Reproduce well at salinities up to 5-10 ppt
Blue Tilapia Reproduce well at salinities up to 5-10 ppt
Mozambique Tilapia Reproduce well at salinities up to 10-15 ppt

Temperature

Tilapia are warm water fish and usually exposing them to temperatures lower than 50 to 52° F is lethal. Blue tilapia can tolerate somewhat temperatures down to 48° F. This limits tilapia commercial farming potential in temperate regions.

Tilapia Activity
Temperature Range
Feeding Stops below 63° F
Harvesting Stress and mortality from handling increases below 65° F
Reproduction Best above 80° F, no reproduction below 68° F
Growth Optimal from 82-85° F

Dissolved Oxygen

Tilapia are able to tolerate dissolved oxygen levels less than 0.3 mg/L, a level that would prove fatal to most other farmed fish.

Although tilapia can tolerate low oxygen levels, they grow best when oxygen levels are kept about 1 mg/L. For better growth, maintaining oxygen levels above 4 mg/L is preferable. This may require some aeration in high density cultivation situations.

pH

Tilapia can survive in pH ranging from 5 to 10, but optimal pH is between 6
to 9.

Ammonia

The tilapia can tolerate high ammonia. Increasing ammonia concentrations increases the stress on the tilapia.

Ammonia Level
Effect on Tilapia
0.08 mg/L or above Depressed feeding
0.2 mg/L or above Some mortality occurs
1 mg/L or above Mortalities, particularly among fry and juveniles
2 mg/L or above Massive mortality

Nitrate

High concentrations of nitrate stresses fish because nitrate limits the ability of hemoglobin to transport oxygen within the body. Tilapia can tolerate higher nitrate levels than many other cultured freshwater fish.

For optimal cultivation, nitrate concentrations should be kept below 27 mg/L. To prevent nitrate problems in recirculating systems, chloride concentrations are often maintained at 100 to 150 mg/L chloride.

References:

Popma, Thomas and Michael Masser, Tilapia: Life History and Biology, Southern Region Aquaculture Center, Pub. No. 283, 4p.

Broders, Adam, Matt Douville and Megan Slonski, Best Practices for Small to Medium Scale Tilapia Aquaculture, WPI, 2005, 102 p.