3. GENERAL CONSIDERATIONS IN THE CHOICE OF CULTURE SYSTEM/APPROACH

3.1 Development Goals and Target Beneficiaries
3.2 Culture Species
3.3 Technology Availability
3.4 Availability of Inputs and Support Facilities
3.5 Investment Requirements
3.6 Environmental Considerations

The selection of the aquaculture system or approach to adopt in a particular development, is determined by several factors including the following:

(i) Development goals/objectives and target beneficiaries.
(ii) Acceptability/marketability of culture species.
(iii) Availability and level of technology.
(iv) Availability of production inputs and support facilities and services.
(v) Investment requirements, and
(vi) Environmental considerations.

3.1 Development Goals and Target Beneficiaries

A primary consideration in the choice of appropriate culture system/approach would be the underlying goals/objectives of the proposed development and the beneficiaries it envisions to assist.

Development objectives, as discussed in the preceding section, can include any or all or a combination of the following:

(i) Increased supply/production of fish for local/domestic consumption.
(ii) Employment/livelihood generation and improved income levels.
(iii) Greater foreign exchange revenues, and
(iv) Socio-economic development and the expansion of ancillary industries.

Aquaculture development, when pursued by the private sector on a commercial scale, is usually undertaken primarily for financial profit. In contrast, government-led and implemented aquaculture projects may be motivated principally by socio-economic goals like the provision of alternative employment and livelihood opportunities for municipal/artisanal fishermen, or the generation of greater foreign exchange earnings for the country.

Depending on the specific project goals and the target beneficiaries, the approach to aquaculture development may be small-scale, low-input, and low-technology or large-scale, high-investment, and high-technology, as the case may be. If the project is envisioned to help coastal subsistence fishermen improve their socio-economic condition, the approach to be taken must necessarily involve small-scale farming which requires low capital outlay, low technology, and low risk, as in seaweed farming, mollusc culture, or tilapia cage culture. On the other hand, commercial aquaculture operations can be as large-scale, high-input, and high-risk as the owners can afford, as in highly intensive shrimp fish ponds or large-scale fish pen operations.

3.2 Culture Species

The choice of culture species is, in more ways than one, closely linked with the objectives of the development and therefore the strategy/approach to be used to achieve set goals. Not all fish species are suitable for aquaculture. By the same token, some cultivable species are more appropriate for large-scale, commercial aquaculture rather than for small-scale operations, as exemplified by the high-value shrimps, the production of which can hardly be undertaken profitably on a small scale. Also, some species are best cultured using specific types of enclosures; for example, penaeid shrimps are best cultured in fish ponds rather than in fish pens, and certain species are more acceptable in certain countries than in others (Table 3).

The choice of species for culture depends on a number of factors including the availability of suitable sites for culture, the biological characteristics of the indigenous or introduced/exotic species, their suitability for culture, and their acceptability in the local or international markets, and the availability of technology and other requirements for their culture.

Table 3. Principal aquaculture species in Asia

Common Name	Scientific Name	Culture System*	Environment**
FINFISHES
Milkfish	Chanos chanos	E, S, I	F, B, S
Freshwater eel	Anguilla japonica	EX, E, I	F
	Anguilla spp.
Grey mullet	Mugil cephalus	EX, E, I	F, B, S
Cockup	Lates calcarifer	EX	F
Grouper	Epinephelus spp.	EX	S
Porgy	Mylio macrocephalus	EX	S
	Mylio spp.
Red porgy	Chrysophry major	S, I	S
Black porgy	Acanthopagrus schlegeli	S	B, S
Tilapia	Oreochromis mossambicus	SI	F. S
	O. nilotica	E, SI	F, S
	Tilapia zillii	S	F
	O. aureus	S	F
	O. mossambicus x O. niloticus	S	F
	O. niloticus x O. aureus	S	F
Red tilapia	Oreochromis spp.	S, I	F, B, S
Sweet fish, ayu	Plecoglossus altivelis	I	F
Common carp	Cyprinus carpio	E, S	F
Goldfish (wild)	Carassius auratus	E, S	F
Crucian carp	Carassius carassius	E, S	F
Puntius carp	Puntius gonionotus	E, S	F
	Puntius spp.
Rohu	Labeo rohita	EX, S	F
Mrigal	Cirrhina mrigala	EX, S	F
Bottom carp	Cirrhina molitorella	E, S	F
Catla	Catla catla	EX, S	F
Grass carp	Ctenopharyngodon idellus	E, S	F
Black or snail carp	Mylopharyngodon piceus	E, S	F
Silver carp	Hypophthalmichthys molitrix	EX, E, S	F
Bighead carp	Aristichthys nobilis	EX, E, S	F
Nilem	Osteochilus hasselti	EX, E	F
Walking catfish	Clarias batrachus	E, S	F
	Clarias spp.
MOLLUSCS
Japanese oyster	Crassostrea gigas	E, I	S
Hard clam	Metrix lusoria	I	S
Small abalone	Haliotis diversicolor	I	S
Corbiculas	Corbicula fluminea	E	F
	C. formosa	E	F
Purple clam	Soletellina diphos	E	S
Apple snail	Ampullarius insularum	S, I	F
Blood clam	Tegillarca granosa	S	S
	Crassostrea malabonensis	E	S
	C. iredalei	EX, E	S
	C. palmipes	S	S
	C. cuculata	EX, S	S
	C. lugubris	E	S
	C. belcheri	E	S
	C. commercialis	S	S
	Metrix metrix	EX, S	S
Cockle	Andara granos	E, S	S
Green sea mussel	Mytilus smaragdinus	EX, E, S	S
REPTILES
Soft-shell turtle	Trionyx sinensis	I	F
Crocodile	Crocodilus siamensis	I	F
	C. porocus	I	F
AMPHIBIANS
Bull frog	Rana catasbiana	S	F
Tiger frog	Rana tigrina	I	F
SEAWEEDS
Gracilaria	Gracilaria spp.	E	B, S
Nori	Porphyra spp.	E	S
Wakame	Undaria pinnatifida	E	S
Green laver	Monostroma nitidum	E	S

*EX = experimental, E = extensive, S = semi-intensive, I = intensive
**F = freshwater, B = brackish water, S = saltwater

Source: Liao, 1988

Huet and Timmermans (1972) list the following criteria for evaluating the suitability of a species for culture:

(i) It must withstand the climate of the region in which it will be raised. Thus, the rearing of coldwater fish like salmonids and trout is limited to temperate regions or mountain areas of tropical countries because they can not tolerate warm water with its low oxygen content.

(ii) Its rate of growth must be sufficiently high. Small species, even if they reproduce well in ponds and accept formulated diets, are not the most suitable for rearing. Also, the best culture species are those which are low in the food chain, e.g., plankton feeders, herbivores, and detritivores. Their culture is also least expensive, even on an intensive scale, because they do not need to be given diets which have a high content of animal protein.

(iii) It must be able to reproduce successfully under culture conditions. Species for culture should be able to reproduce in captivity/confinement without needing special conditions that have to be fulfilled, and which give high returns on eggs and fry. Although it is possible to rear species whose reproduction in confinement is not possible at all (e.g., some carps) or whose reproduction under hatchery conditions has not yet been possible on a commercial scale (e.g., milkfish in the Philippines), the sustainability of the grow-out operations is hampered by the seasonal unavailability of wild fry for stocking in fish pens and/or fish ponds.

(iv) It must accept and thrive on abundant and cheap artificial food. Culture species which feed on cheap artificial feeds and give low feed conversion ratios (FCRs), also tend to give very good production rates, thus bringing in better financial returns.

(v) It must be acceptable to the consumer. Even if all the foregoing criteria are met by a candidate species, it is not worth culturing if there is no market for it. It is possible, though, to promote acceptability of or encourage consumption of a particular species to ensure that it will eventually sell in the market. (This was the situation with tilapia in the Philippines prior to the introduction of the bigger-sized, lighter coloured S. niloticus in the early 1970s.)

(vi) It should support a high population density in ponds. Social and gregarious species which can grow well to marketable size even under high density conditions in ponds or tanks (e.g., tilapia) are preferable to those which can be grown together in dense numbers only up to a certain age beyond which they eat each other (e.g., pike).

(vii) It must be disease-resistant. Reared fish must be resistant to disease and accept handling and transport without much difficulty. Tilapia is an ideal species for culture because of its high resistance to disease even in highly intensive culture systems.

A wide variety of fish and aquatic resources is cultured in freshwater, brackishwater, and marine environments world-wide using different methods (Table 4). Rabanal (1988a) estimates that there are close to 50 species of freshwater, brackishwater, and marine finfish species; about 13 crustacean species, 13 molluscan species, 5 seaweed species, and 5 economic aquatic vertebrates (frogs and other amphibians and turtles and other reptiles) cultivated in Southeast Asia.

Liao (1988) lists some 25 major finfish species, 18 molluscan species, 2 reptile species, 2 amphibian species, and 4 seaweed species as the principal species cultured in Asia (Table 4). To the list could be added the crustaceans consisting of the brackishwater/marine penaeid shrimps (mainly Penaeus monodon, P. semisulcatus, P. japonicus, P. orientalis, P. merguiensis, and Metapenaeus ensis) and the freshwater prawn of the genus Macrobrachium; the seaweeds Eucheuma, Laminaria, and Porphyra; and marine finfishes like sea bass and groupers (Baluyut, 1989a).

Table 4. Examples of aquaculture practices employed in different countries for different species

Country	Species Raised			Mode of Culture	Reference
NEPAL	Common carp, Chinese carp, Indian carp			Integrated fish farming	Pullin, 1989
THAILAND	Penaeid shrimps, freshwater prawn (Macrobrachium)			Pond and cage culture in freshwater and brackishwater	Sirikul, et al., 1988
	Cockles and mussels			Mariculture along the coast
	Finfishes			Cages suspended in rivers and standing waters
		Clarias batrachus
		C. macrocephalus
		Tricnogaster pectoralis
		Pangasius sp.
		Lates calcalifer (sea bass)
		Epinephelus spp. (grouper)
INDIA	Indian carps			Integrated rice-fish culture	Mukhopadhyay, 1989
YUGOSLAVIA	Primary species:			Pond culture	Wurtz, I960
			Table carp
			Aischgrund sp.
			Croatian sp.
	Secondary species:
			European catfish
			Tench
			Pike
POLAND	Carp, tench, pike			Pond culture	Ackefors, 1989
EAST GERMANY	Carp, tench			Pond culture	Ackefors, 1989
ECUADOR	Penaeid shrimps			Pond culture	ADCP, 1989b
EL SALVADOR	T. aurea			Pen culture; floating cage culture	FAO, 1986
	T. mossambica
GUATEMALA	Tilapia and carp			Cage and pond culture	FAO, 1986
COSTA RICA	Tilapia			Pond and cage culture	FAO, 1986
	Trout			Semi-intensive pond culture
	Chinese carp
	Freshwater shrimp
	Crayfish
	Giant clam
	(Anodontis luteola)
ECUADOR	Trout			Intensive pond and cage culture	FAO, 1986
	Trout, marine shrimp			Extensive culture
AUSTRALIA	Salmonids, marine shrimps, molluscs			Intensive/semi-intensive pond culture	Nelson, 1988
FRENCH
POLYNESIA
GUAM	Giant clam, seaweeds, and pearl oysters			Open water culture
NEW CALEDONIA
NEW ZEALAND	Tilapia, milkfish, catfish, freshwater prawns, and crayfish			Less intensive onshore pond farming

In Africa, the predominant species are the tilapias, carps, mullets, sea bass, and catfishes; in addition, some salmonids, miscellaneous freshwater fish, molluscs, and crustaceans are also cultured. Latin America grows miscellaneous exotic fish and marine shrimps, molluscs, and salmonids. Successful experiments on the artificial reproduction and pond culture of indigenous finfishes of the genus Colossoma and Piaractus (locally known as "tambaqui" and "pirapitinga" in Brazil, "cachama" and "morocoto" in Venezuela, "gamitama" and "parco" in Peru, and "cachama negra" and "cachama blanco" in Colombia) also give promise of increased yields (Saint-Paul, 1989). The Caribbean rears tilapia, carp, marine and freshwater crustaceans, oysters, and seaweeds; in the Mediterranean region, salmonids are the prime fish and carps are secondary fish. In the Pacific, tilapia, milkfish, catfish, salmonids, marine and freshwater crustaceans, molluscs (including giant clams and pearl oysters), and seaweeds are cultured but mostly on a pilot/experimental scale (ADCP, 1989a).

3.3 Technology Availability

As aquaculture involves the application of certain methods and techniques in the breeding and rearing of fish and other aquatic species, the selection of a particular culture system will necessarily depend on whether or not the technology for such is available in the country or project area and if so, its level of complexity and/or transferability to the fish farmer beneficiaries.

In general, simple, low-cost, low-technology systems (as for tilapia culture) are easier to transfer to the end users and have greater chances of success as compared to more sophisticated/complicated and relatively high-technology systems like those involved in penaeid hatchery and farming, especially using intensive culture techniques.

Thus, if aquaculture is being considered as an alternative livelihood for displaced coastal fishing families, the preferred system is one that will require the use of simple techniques and low-cost production facilities whose construction and operation may involve entire families or communities, e.g., seaweed and mollusc farming. On the other hand, more complex technologies which require higher capital and other inputs and which promise better profits, are usually adopted by medium- to large-scale entrepreneurs who have the capability to engage the services of technical specialists in running their operations.

3.4 Availability of Inputs and Support Facilities

Corollary to the level of technology is the ready availability of the production inputs, mainly seed and feeds, and ancillary facilities and services like hatcheries, feed mills, processing plants, ice plants, and cold storages. At the grassroots level, it is essential that not only are the production inputs available, the fish farmers should be adequately provided with technical assistance including training and extension support. For large-scale, intensive, commercial operations, especially those geared for the export market, the constant availability of seed and feeds is critical as well as the existence of adequate post-harvest handling and processing facilities to ensure high quality products.

3.5 Investment Requirements

The magnitude of financial investment required to set up, operate, and maintain an aquaculture operation depends on the level of technology involved and the type of culture system adopted. In general, the investment requirement Increases as a function of technology level and degree of complexity of the culture system, with extensive systems requiring the least capital investment and intensive systems needing the most.

Thus, as mentioned earlier, small-scale aquaculture development projects which involve simple production facilities (like rafts and stakes for mollusc culture and bamboos and ropes for seaweed farming) require minimal financial inputs. In contrast, highly intensive, highly complicated production systems, as those used for intensive shrimp grow-out operations, require large outlays not only for initial development but also for operation and maintenance.

The major cost items in aquaculture production, as in any other type of agriculture, include initial development and pre-operating costs including cost of land/site acquisition, production inputs (seed, feed, fertilizers, pesticides), and operating and maintenance costs (including cost of labour, power, supplies and materials), and miscellaneous expenses including harvesting and marketing costs.

Where investment costs are high and land and labour are limited and costly, as in Japan and Taiwan (PC), the trend will be intensification to achieve maximum yields per unit area. Where land, labour and fish are inexpensive and feed is unavailable or costly, as in the Philippines and Indonesia, the trend is for extensive culture utilizing larger pond area and natural food.

3.6 Environmental Considerations

Much concern has been raised over the potential adverse impacts of aquaculture on the environment, especially as a result of intensive culture. Taiwan (PC) and the serious shrimp disease and water quality problems it presently faces as a result of the tremendous expansion of its intensive shrimp industry, is the best example one can think of at the moment.

The widespread destruction of mangrove forests to give way to fish ponds, has also disturbed the ecological equilibrium in a number of coastal zones, reducing aquatic productivity and eliminating breeding and nursing grounds of important species of fish and other aquatic life, among others.

In Australia, the possibility of eutrophication of natural waters from high nutrient loads discharged from fish ponds is a subject of concern (Jamandre, 1988). In Negros Province in the Philippines, a continuing debate between two main industries - aquaculture and sugar - over industry standards, remains unresolved as wastes discharged by sugar refineries into the river used by aquaculture farms as a water source, have reportedly caused increased temperature and acidity levels that have disastrous effects on the shrimp farms (Cayco, 1988).

Aquaculture can produce a number of negative impacts on the environment (Table 5). It is therefore important to take environmental considerations into account in selecting the culture system to adopt, either by reducing the extent to which aquaculture practices interfere with the ecology of the aquatic milieu or by making the milieu itself more amenable to the aquaculture pursuit (UNDP/NORAD/FAO, 1987).

Concern that coastal aquaculture can have adverse impacts on the coastal environment has prompted a number of authors to suggest practical guidelines for siting and operating aquaculture installations in mangrove systems. Kapetsky (1982) summarizes these as follows:

(i) Establishment of types of aquaculture which do not involve destruction of mangroves and associated flora and fauna, e.g., fish cages and fish pens in open water areas.

(ii) Integrated aquaculture and forestry, e.g., planting of mangroves along fish pond dikes and other nearby suitable areas.

(iii) Preservation of a functional ecosystem by means of:

- establishment of aquaculture in areas already reclaimed from mangroves rather than on productive mangrove stands, where possible;

- utilization of the least productive parts of the mangrove forest or those with the lowest value trees;

- locating aquaculture sites toward the landward side of the mangroves to preserve the productivity of the most productive portions for capture fishery resources;

- ensuring that the Area occupied by ponds and other elements of the farm should be small in relation to the overall area of the mangrove system in which they are installed.

(iv) Paying ample attention to site selection, culture installation design, and the management of culture operations.