Aquaculture

Introduction

  • Aquaculture is the farming of aquatic organisms (fish, crustaceans and plants) in freshwater, seawater or brackish water. 
  • Kenya has a great potential for commercial aquaculture to fill the gap in national fish supply due to the declining wild caught fish from rivers and lakes.
  • Aquaculture provides food security, employment opportunities and reduce poverty among households. Aquaculture is done in:
  • Semi intensive systems- pond fertilization is done alongside feeder e.g. Ponds  
  • Intensive systems - fish are stocked and high densities with complete feeding e.g. Recirculating aquaculture (RAS), cages and aerated ponds.
Culture systems
Culture systems  

Pond based production systems
  • Ponds are natural enclosed water bodies used for fish farming.
  • They are either dug out earthen ponds or lined ponds in places where soil is sandy.
  • One earthen pond of 300m2 cost approx. KES 35,000 while a liner pond cost approx. KES 60,000.
  • Production in ponds is approx. 2 tonnes/ha/ year. 

Recirculating aquaculture systems (RAS)
  • These closed and semi-closed systems intensively used to cultivate fish and reuse a large proportion of treated culture water to reduce water and power consumption. 
  • Production in a RAS is 50 kg/m3 per production cycle. RAS is recommended in urban and peri-urban areas 

 

Culture systems  

Aquaponics systems

 
  • Aquaponics is the integration of recirculating aquaculture system (RAS) and hydroponics in one production system.
  • Fish waste are used for the growing vegetables.
  • A small cost aquaponic unit requires an initial capital of KES 150,000.
  • Production of fish is 25Kg /m3

Integrated culture systems
  • Fish production is mixed with either rice, crops or livestock farming.
  • The production is 1.5 to 174 kg/ha/season
  • Wastes from crops and livestock are used as feed/pond fertilizer, and fish wastes are used to fertilize the crops

Low volume, high-density (LVHD) cages

  • Small cages, with low volume stocked at very high stocking density.
  • Stocking density in these cages ranges from 120- 150 fish / m3.
  • Production from is estimated at 1,000-5,000 tonnes/year. 
  • The investment cost for commercial cage farming is KES 300,000.

Breeds
Breeds  

Improved Nile tilapia [F7-2017-01]

]

 
  • F7 is an improved strain of Nile tilapia that has undergone selective breeding.
  • It has better growth compared to wild stocks, uses less feed, and has improved flesh to bone ratio.
  • For better yield good aquaculture, practices have to be implemented in farming of this improved strain.

Improved Marine Tilapia

(Photo by Dr. Mirera)
  • Marine tilapia is an improved breed of Nile tilapia (Oreochromis niloticus) that has been acclimatized to live in marine environment.
  •  It tolerates higher salinity levels of 40 ppt,
  • It is suitable for culture in brackish water and seawater of salinity levels above 10ppt.
  • The breed is available at KMFRI Mombasa Centre

Improved Catfish Strain [F3-2017-01]
  • F3-2017-01 is an improved strain of catfish developed through hybridization.
  • The crossbreed had a higher survival (78.8%) rate; higher final body weight (327g in 4 months) and better Food Conversion Ratio (FCR) (1.25).
  • They are relatively uniform in size and has reduced cannibalism.
  • The cost of the broodstock is KES 600 per kg.

 

Breeds  

Indigenous Fish Species ( Victoria tilapia (Oreochromis variabilis), Singida tilapia,(Oreochromis esculentus), Jipe tilapia, (Oreochromis jipe)

 
  • Are found in Lake Victoria, Lake Jipe and Lake Baringo.
  • They have high culture potential.
  • The fish have been bred in captivity in their respective ecological zone.
  • They are alternative species for aquaculture that can adapt to climate change.

Barbus altianalis and  Ningu, Labeo victorianus

(Photo by Jacob abwao)
  • Ningu has demand within local communities and has been evaluated for recruitment to aquaculture.
  • Barbs has been brought into captivity recently and has been able to adopt well at KMFRI, Kegati Research Centre.

Coastal aquaculture species

 

Milkfish (Chanos chanos)
  • It is endemic to the brackish water environment.
  • It is suitable for culture in the intertidal areas.
  • Milkfish can be cultured together (in polyculture) with shrimps in ponds.
  • The fish can grow to 300 – 600 g in 8 months.
  • Its suitable for culture in Kilifi and Kwale counties.

Red snapper (Lutjanus argentinamaculus)/ (Tembu)

Photo from http://bigfish.co.ke/red-snapper.html
  • It is cultured in mangrove buffer zone covering 20-100m.
  • Stocking density is about 5,000/ha.
  • It requires high protein feed (48-50%).
  • Its suitable for culture in Lamu, Kilifi and Kwale counties.

Mud crab (Scylla serrata) (Kaa)
  • The young crabs are put in plastic or bamboo cages
  • Production is 300 tonnes/year in cages.
  • Fattened crabs sold at 600 /kg.

Prawn (Penaeus monodon) (Kamba)
  • Cultured in ponds of 100 to 200 m2 near the sea.
  • Suitable for culture in Kilifi and Kwale counties

Sea weed  (Kappaphycus alvarezii)

(Photos from KMFRI state of aquaculture report)
  • Cultured in floating rafts in sandy or rocky areas of in the inter-tidal zone.
  • Required temperature of 27°C and 30°C and salinity 30 to 34 ppt.
  • Suitable for culture in Kilifi and Kwale counties
  • The selling price of seaweed is KES 30/kg of dry weight
   

 

Site selection

For all aquaculture species the site for aquaculture should have the following attributes: -

  • Have adequate quality water which supports the requirements of the species cultured.
  • Have a gentle slope (5-10%) for land based aquaculture.
  • Large enough to allow for construction and future expansion.
  • Free from sources of contamination.
  • Free from heavy metals and pesticide residues.
  • Away from sewage pollution and upstream of any form of discharge.
  • Suitable to support the life of the species being cultured.
  • Safe from destruction and theft.
  • Away from thick vegetation that harbor predators. 
Feed Formulation
  • Feed formulation is done for all fish species depending on their nutritional requirements. Fish require different feeds at different stages of life (fry, fingerling, grow out and broodstock).
  • Nutritional considerations are made for protein, amino acids lipid, fatty acids, vitamins, minerals, and energy requirements for normal growth and healthy fish.
  • Grow out fish performs better when fed feeds with crude protein level between 26 to 40%
  • Fish feed ingredients are selected based on availability, low cost, and simplicity of handling during processing.
  • Common ingredients are:-
    • Roots and tubers (Cassava, sweet potato leaves).
    • Cereals and cereal by-products (maize meal, maize germ, maize bran, wheat pollard, wheat bran, rice bran, brewers waste).
    • Oil-seed cakes (cotton, sunflower, soybean, groundnut, canola).
    • Feeds of animal origin (Blood meal, Fish meal, Fish offal, hydrolyzed feather meal and Black soldier fly larvae meal).
  • Feed formulation is done by Pearson square method or linear programming which uses a computer software.
  • The nutrition composition of the formulated feed should be according to the Kenya bureau of standards Feed standards.

Feed management practices
  • Feeds should always be bought from certified feed suppliers.
  • Feed should be utilized within the shortest time after purchase to a maximum period of three months.
  • Feed should be stored in raised racks/pallets away from any form of moisture.
  • Feed should be stored in a cool, dry and well ventilated place.
  • Feed store should be kept clean and free from pests.
  • Feed with high moisture, mould, or rancidity should be disposed of according to guidelines.

Feeding equipment

For all fish being cultured feeding is either done by hand or mechanized. The mechanized feeding equipment

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