Milkfish Culture in Sea Cages

Milkfish (Chanos chanos) is an important food fish in the Philippines, Taiwan and Indonesia. It is a popular fish for culture because it tolerates a wide variety of salinity, temperature and water quality, adapts well to high density, and reaches marketable size in 4-7 months.

According to the Food and Agriculture Organization (FAO), the most important milkfish producers for 2006 are the Philippines with 315,074 metric tons (mt), Indonesia with 212,932 mt, and Taiwan with 56,135 mt. This comes up to a combined value of about US$645 million.

Milkfish can be raised either in extensive, semi-intensive and intensive systems. Culture areas include ponds, pens or cages. Milkfish ‘seeds’ for culture can be sourced either from the hatchery or from wild stocks.

Culture of milkfish in marine cages is intensive, characterized by a small area, high levels of inputs like seeds and feeds, which result to high yields. Milkfish farmers in the Philippines are finding it advantageous to culture fish in mariculture parks.

Why Mariculture?

• Land resources are becoming scarce
• The vastness of the sea remains the last frontier for fish production
• Mariculture profitability has been established
• Could provide fisherfolk with alternative sources of income
• Demand for fish continues to grow with increasing population
• Wild catch from the sea is declining due to overfishing

Why Raise Fish in Mariculture Park?

• The park concept provides farmers technical assistance and water monitoring services, moors and cage frames
• Fish farmers spend only for nets, feeds, seed stock and other inputs
• The park may also include on-site guard house, feed warehouse, net mending & drying shed, communication and  transportation facilities, and guest houses

Where are the Mariculture Zones (MZ) in the Country?

The Bureau of Fisheries and Aquatic Resources (BFAR) of the Department of Agriculture has established mariculture parks throughout the Philippines, with plans of establishing several more in the future.

Early Warning for Pollution

Milkfish sea cage operators may soon be warned of impending water pollution that may kill their stock. SEAFDEC is currently developing an early warning system to guard against the negative impacts of fish cages in mariculture parks.

Intensive rearing of milkfish in cages uses a much higher amount of input like feeds. Feeds that are not eaten or digested properly, plus other waste products go into the water and some will eventually settle onto the sediment bottom and may cause marine and sediment pollution. It is therefore necessary to monitor the water and sediment quality around the fish cages.

The operator could also check the feeding regime, avoid overfeeding of stocks, and use only good quality formulated feeds to help reduce wastes. The cage operator may likewise step-up the water monitoring parameters.

Pollution not only affects the fish in the cages. The toxic conditions could impact infauna, or animals living within submerged sediments. These include polychaetes, marine worms which play an important role in the marine environment. Their burrows contain microorganisms which produce enzymes that degrade organic matter.

What the operators of fish cages or mariculture parks need to do is periodically collect soil samples under the cages, and compare these to a color chart being developed by SEAFDEC. A reference color will let them know how far off or how near they are from ideal conditions. This method is basically the same technique used by rice farmers to see if their rice needs additional fertilizer.

If there are early signs of pollution, the fish cage operators are advised to observe a “fallow period” by moving the cages to another area in the mariculture park to allow the sediments and infauna to recover.

Site Selection

The following should be considered in selecting a site for the cage culture of milkfish:

• Free from pollution
• Protected from adverse weather condition
• Accessible but secured from poachers
• Should be at least 12-15 meters deep
• Far from seagrass and coral beds

Cage Design and Construction

• Net squares or rectangles measuring 10 x 10 m with a depth of 6 m
• Frames made of bamboo, lumber, GI or HDPE pipes
• Floats made of styrofoam, empty plastic containers
• Mooring made of cement blocks, GI pegs or anchors
• Sea cage may be arranged in quadrant or in clusters

Culture Condition

• Area of cage: 600 cubic meter
• Stocking density: 35 cubic meter
• Size of fingerling: 5-6 inches
• Amount of feed: 24,937.7 kg
• Feed conversion ratio (FCR): 2.5
• Duration of culture: 120 days
• Survival rate: 95%

Harvest

• Average body weight (ABW): 0.5 kg
• Total harvest: 9,975 kg
• Selling price: P95

Investment Requirements in Php (2009 data)

Capital outlay:

• Bamboo cage frame with drum floats and mooring system (2 units) – 55,000
• Net cages (10 x 10 x 6 cm) – 59,750
• Motorized boat – 25,000

Working capital (1 crop)

• Fingerlings – 115,500
• Feeds – 623,438
• Maintenance (5% of capital) – 7,561
• Family labor (P3,000/month) – 18,000
• Marketing expenses: 66,334

Total investment – P 830,833

Economic Analysis (in Php)

Sales: 947,625

• Less expenses (fingerlings, feeds, maintenance, marketing, labor): 830,833
• Depreciation ( 5 years): 13,975
• Total cost: 844,808

Net income:

• 1 run – 102,817
• 1 year ( 2 runs) – 205,634

Return of investment for 1 year: 21%

Payback period: 4.16 years

For more information and inquiries, contact:

SEAFDEC Aquaculture Department
Tigbauan, Iloilo
Tel. : (033) 511-9170 Fax : (033) 511-9070
Email : aqdchief@seafdec.org.ph
Web: www.seafdec.org.ph