Aquaculture feeds and fertilizers
Carp in fish ponds can feed themselves by touching the rod that extends from the automatic fish-feeder into the water
Global aquaculture production has grown at 11 percent a year over the past decade and is projected to continue increasing. Along with this growth, there has been a trend within most developing and many developed countries toward the increased use of artificially compounded feeds (aquafeeds) for farmed finfish and crustaceans.
This trend has been particularly apparent in developing countries with the progressive intensification of farming systems. In the main Low-Income Food-Deficit Countries compounded feeds are increasingly being used for the production of both lower-value staple food fish species (mainly freshwater finfish such as carp, tilapia, and catfish) and higher-value cash crop species for luxury or niche markets (mainly marine and diadromous species such as shrimp, salmon, trout, yellowtail, seabass, seabream, and grouper). In fact, the production of aquafeeds has been widely recognized as one of the fastest expanding agricultural industries in the world, with growth rates in excess of 30 percent per year.
Asia is by far the leading region in aquaculture production where the bulk of Asian finfish and crustacean aquaculture is obtained in semi-intensive pond farming systems. The great majority of these farming systems, particularly for freshwater non-carnivorous finfish production (which accounts for over 80 percent of the total finfish production in Asia), depend on the use of natural foods through proper pond fertilization using inorganic and organic fertilizers, supplemented with prepared feeds.
Generally speaking, pond fertilization is important to increase the availability of natural foods for fish and crustaceans. The pond water can be fertilized with purchased inorganic fertilizers, or locally available organic fertilizers may be used, e.g. compost made with plant and animal wastes, animal manure, or plant material
The prepared feeds range from single feeds available on-farm such as grass or rice bran to farm-made formulated feeds and commercial feeds. This includes aquatic and terrestrial plants (duckweeds, azolla, water hyacinth etc.), aquatic animals (snails, clams etc.) and terrestrial-based live feeds (silkworm larvae, maggots etc.), plant processing (de-oiled cakes and meals, beans, grains and brans) and animal-processing by-products (blood and feather meal, bone meal etc.). Formulated commercial feeds are composed of several ingredients in various proportions complementing each other to form a nutritionally complete diet.
If the aquaculture growth potential is to be realized and maintained, then considerable quantities of nutrient inputs in the form of fertilizers, supplementary feeds or complete compound aquafeeds will have to be available on a sustainable basis. In this context, establishing good aquafeed manufacturing practices is important for aquafeed producers. National surveys and documentation concerning feed and fertilizer resources and their availability and use could be very helpful for fish farmers
Study of algae to be used as food for prawn larvae
Aquafeed development faces two major global challenges
1) The need for finfish and crustacean farming systems to develop feeding strategies based wherever possible upon the use of non-food grade locally available feed resources
Aquaculture needs to further increase its net contribution to total world fish supplies. At present, nearly all farming operations for carnivorous diadromous finfish, marine finfish and crustaceans - based on the use of aquafeeds - are net fishery resource `reducers' rather than `producers'. The quantity of inputs of dietary fishery resources in the form of fishmeal, fish oil, crustacean by-product meals, `trash fish', etc. exceeds outputs in terms of farmed fishery products by a factor of two to three. Long-term efforts must be placed on the use of by-products from the large agricultural production sector, including terrestrial animal by-product meals resulting from the processing (i.e. rendering) of non-food grade livestock by-products; plant oilseed and grain legume meals; cereal by-product meals; and miscellaneous protein sources such as single-cell proteins, leaf protein concentrates, invertebrate meals, etc.
2) Improved feed formulation and on-farm feed and water management strategies tailored to the needs of the farming system or farm production unit
As farming systems intensify, either in terms of increased stocking density and consequent nutrient input or in terms of number of farms per unit area, the need to develop environmentally cleaner or 'greener' feeding strategies becomes greater. The net results of excess nutrient loss are an economic loss to the farmer with a potential deterioration of the aquatic environment within and possibly outside the farm, subsequently increasing stress on the cultured animals and increased susceptibility to disease. Thus, feeding regimes should be designed to minimize nutrient loss and faecal output, and to maximize nutrient retention and the health status of the cultured species. Such actions would in turn help to improve the social acceptance of and confidence in the sector in terms of aquatic resource use and environmental sustainability. In this respect, feed manufacturers have the very important responsibility of ensuring that the feed they provide to farmers is both nutritionally correct for the intended farming production system and is managed correctly by the farmer.