FISH PRODUCTION IN INTEGRATED FARMING SYSTEMS

Yap Siaw-Yang
Institute of Advanced Studies
University of Malaya
59100 Kuala Lumpur
Malaysia

ABSTRACT

This paper outlines the farming technology of fish production in integrated aquaculture-livestock farming systems and defines ways to attain high fish production. Fish production figures reported in published literature varies from 1.5 tonnes/ha of fish pond/year to 18 tonnes/ha of fish pond/year. The higher fish production is attainable through intensive management inputs, involving high stocking densities of complementary-feeding fish species, addition of energy-rich supplementary feed to a significant component of natural feed, and aeration of fish pond water. Intermittent harvesting of fish at slow phases of fish growth curve may further increase fish production of integrated farming systems.

INTRODUCTION

Integrated livestock-fish farming is a practice which links together two normally separate farming systems, whereby the livestock and fish become subsystems of a whole farming system. Emphasis focuses on an optimal waste or by-product utilization efficiency in which the waste of one subsystem (livestock) becomes an input to a second subsystem (fish). The integration of livestock with fisheriesaquaculture has received considerable attention lately with emphasis on the incorporation of animal manures as fertilizer and nutrient for promotion of natural feed in fish ponds (Delmendo, 1980; Wohlfarth and Schroeder, 1979). The recent surge of interest in integrated farming systems is due to the growing concern for maximizing productivity through optimum utilization of resources and to improve the diminishing per capita resources. The integration of duck and chicken with fish polyculture systems is amongst the most popular in Asian countries (Sin, 1980 in Hong Kong; Wetcharagarun, 1980 in Thailand), followed by pig-fish and ruminants (cattle)-fish production systems (Chen and Li, 1980 in Taiwan; Cruz and Shehadeh, 1980). A more sophisticated integrated farming system is practiced in China; Chinese livestock-fish integrated farms may have complex interactions between livestock, crops and fish. In some Chinese farms, significant off-farm inputs to feed the fish such as aquatic macrophytes, snails and a wide variety of agricultural by-products are practised even though the pig may be the major livestock integrated with fish.

Promotion of livestock-fish integrated farming is viewed as a developmental strategy in overcoming a food crisis through enhancing waste and land-space utilization efficiency. The farming system improves space utilization and land-use conflicts in which the two subsystems essentially occupy all or part of the space required for an individual subsystem. The present paper provides an overview on fish production in integrated aquaculture-livestock systems, exploring the fish production levels in integrated farming systems, and ways to attain higher fish production levels.

THE PRINCIPLES OF FARMING TECHNOLOGY OF FISH PRODUCTION IN INTEGRATED FARMING SYSTEMS

Guided by major findings on livestock-fish farming published in a preliminary set of principles defining the various aspects of the culture technology and promotion of fish production in integrated farming systems is suggested and outlined, as a basis for further deliberation. Principles pertaining to technology of livestock-fish farming are:

1. Fish production in integrated systems is more complex than the conventional separate aquaculture system, requiring more knowledge and better management inputs

2. Integrated farming systems may vary in the degree of intensification of the livestock and fish subsystems, varying from extensive, semiintensive to intensive subsystems.

3. Extensive subsystems utilize natural feed produced without international fertilization; semiintensive subsystems require fertilization to produce natural feed and/or supplementary feed but with a significant component of diet supplied by natural feed; and in intensive subsystems all the nutritional requirements are provided by artificial feed given to fishes with natural feed contributing little or no nutrition.

4. Fish cultured in an integrated farming system with livestock (especially duck; Edwards, 1986) benefit from a significant amount of the nutrition derived from natural food, which develops in the pond due to the fertilization by organic manures. This suggests the important role of pelagic algal-based food web which cultivates in fish biomass.

5. The largest contribution of the manure to fish nutrition therefore, appears to be due to its fertilizing effect in the pond. Bacteria, breaking down the organic matter in the manure, release nutrients which lead to the production of phytoplankton and zooplankton.

6. In a manure-fed fish pond, fish nutrition may also be derived from direct consumption of the manure. However, a detritus food web has a secondary role in fish biomass production biomass production, as compared with the algalbased food web.

7. The direct nutritional value of manure for fish is by its content of spilled animal feed. A large proportion of the nutrients in livestock feed are not assimilated, but are voided in the excreta, particularly pig excreta (Edwards, 1985).

8. Over-fertilization with manure may lead to poor water quality of fish pond, particularly leading to depletion of dissolved oxygen and fish kills.

9. Management of water quality is needed to overcome fish kills due to oxygen depletion and extreme fluctuation of dissolved oxygen levels. The strategy is to promote a growing biomass of phytoplankton which will generate sufficient oxygen to maintain relatively high dissolved oxygen have on a 24-hr basis. It is essential to maintain a positive net photosynthesis

10. The criteria for selection of fish species for stocking into manure-fed fish ponds should be based on the ability of fish species to :

    * filter and feed on plankton (bacteria, phytoplankton and zooplankton)
    * tolerate low levels of dissolved oxygen (< 2mg/1 minimum as defined by “Criteria for the Protection of Aquatic Life”)

11. An optimal stocking density of fish species is critical in attaining high cumulative fish yields and in reaching the upper carrying capacity of a manure-fed fish pond.

12. Determination of and recommendation of the optimal stocking density of fish consider differences in local circumstances such as the fish species, manure-type and inputs to the pond, addition of other off-farm feed, and water quality of the pond.

13. Ways to intensify fish production from integrated farming systems involve management inputs to :

    * stock a higher initial fish biomass, followed by
    * harvesting the fish intermediately when the growth curve of stocked fish starts to slow down

14. There is a need for a more complex marketing system to handle the inputs and products from two subsystems as opposed to a single subsystem.

15. Integrated farming on the one hand, enables the distribution of risk (both biological and economic), since two subsystems are involved as opposed to one in a single-commodity farming system; on the other hand, the failure of one subsystem can adversely affect the other.

FISH SPECIES SUITABILITY AND SELECTION

The main objective of manuring is to produce a good growth of plankton, mainly phytoplankton, but also zooplankton and bacteria which are protein-rich natural for fish. On this basis, the most appropriate species of fish for a manure-fed pond are therefore those species which are able to filter and feed on plankton (bacteria, phytoplankton and zooplankton) from the water. The most common filter feeders are carps and mixed feeder on algae-detritus are certain species of tilapia. The most commonly raised carp species are the bighead carp Aristichthys nobilis Richardson and the silver carp Hypophthalmychithys molitrix Valenciennes. The carps are usually raised in polyculture with the grass carp Ctenopharyngodon idella and Indonesian carp Puntius gonionotus Linnaeus controls micro- and macro-vegetation at the water's edge, the Hoeven's slender carp Leptobarbus hoevenii Blk and the common carp Cyprinus carpio Linnaeus which is a bottom feeder. An important observation is that the detritus-feeding silver carp benefited most from the pond conditions, increasing its biomass share from an initial 5.8% to 20.7% from a series of investigation on the integrated farming systems in the Transkei, South Africa. The Indian carps, catla Catla catla Hamilton, mrigal, Cirrhinus mrigala Hamilton Buchanam and rohu, Labeo rohita Hamilton have also been used in experimental duck/fish integrated farming systems in India.

Polycultures of carps have been widely assumed to be the most efficient way to obtain high fish yields but in Taiwan, the percentage of tilapia in the pond has increased markedly at the expense of the Chinese carps. The most commonly raised tilapia species are the blue tilapia Oreochromis aureus Steindachner, the grey tilapia Oreochromis mossambicus Peters, the Nile tilapia Oreochromis niloticus Linnaeus or their hybrids. Tilapia are more suitable than carp for manure-fed ponds since the former are more tolerant to low levels of dissolved oxygen than the latter.

Air-breathing silver-striped catfish Clarias spp., are also integrated with pig farms. The detritusfeeding grey mullet Mugil cephalus L. (De Silva and Wijeyaratne, 1976) may be excellent substitutes for the silver carp in integrated farming systems under saline conditions.

FISH YIELDS AND PRODUCTION RATES IN INTEGRATED FARMING SYSTEMS

There are few data on fish yields from ponds which received livestock manure (and spilled livestock feed). The fish yields in integrated livestock-fish farming systems reported in the literature vary greatly, with the actual and extrapolated equivalents ranging from 1.5 ton/ha/year to 18 ton/ha/yr (Table 1). The variation in fish yield is due:

*   the animal sub-system and its major manure input to the pond
*   the fish species and stocking rates
*   intensification of culture management inputs e.g. addition of other off-farm feed

Different Types and Amounts of Manure Inputs

The rationale behind integrating fish with livestock is the large amount of nutrients (N-P-K) present in the feed that is recovered in the manure, with possible proportions of 72–79% nitrogen, 61–87% phosphorus, and 82–92% potassium. These act as fertilisers in fish ponds to produce plankton which comprise high-protein natural food for certain species of fish.

Nitrogen and phosphorus are the nutrients most likely to be limiting for plankton growth in the pond but fish yield is probably more directly correlated to manure nitrogen content (Edwards, 1991) since nitrogen is more volatile than phosphorus. Based on the nitrogen content of the different manures, it was possible to estimate the stocking density of different livestock (laying duck, dairy cow, pigs and buffalo) in order to produce the same fish yield of 174.7 kg/200 m2/year (equivalent to 8.735 t/ha/year; Edwards, 1983; reproduced in Figure 1) in 13 family-level farms. Considering the livestock's manure characteristics (total live weight, age of livestock, feed characteristics of livestock, climate and management of livestock subsystem) and the varying N contents (% of the manure production/animal/year, i.e. 2.6 % for laying duck manure, 1.9 % for pig, 2.2 % for dairy cow and 1.1 % for buffalo, the estimated number of laying duck, pig, dairy cow and buffalo required to the same fish yields are 1335, 410, 40, and 85 individuals respectively. Prinsloo and Schoonbee (1987a) noted the comparative effectiveness of the manure on the development of organisms in the food web and promotion of biological activity in fish ponds are : duck manure > pig manure > raw chicken manure > cattle manure > sheep manure.

Manure may contain up to 25% crude protein, but more than half of this is usually non-protein nitrogen (e.g. uric acid) which is not assimilated by fish; therefore manure itself is a poor feed for fish. Manures also contain less energy than conventional pelleted feeds. Though many species of fish consume manure directly, it is a low quality feedstuff compared to conventional pelleted feed and natural plankton.

Another advantage of manure utilization in fish ponds is that since carbon forms about 50% of the biomass of plankton, the high organic content of the manure is an important source of carbon which is released by bacterial respiration. However, depending on the productivity and quality of water and soil, the effectiveness of livestock manure (enriched with cellulose-rich organic matter) in acting as nutrient sources for fish growth and in raising fish yield varies. Two possibilities have been observed in Dor, Israel:

1. manure would improve fish yields only under conditions of water and soil which are poor in essential nutrient minerals (e.g. carbonates or organic matter), or of a low pH, fish ponds receiving very “soft” waters deficient in minerals, or ponds with a low primary production (Wohlfarth and Schroeder, 1991); and

2. manure may be ineffective in raising fish yields above the rates achieved by daily applications of mineral (N-P-K) fertilisers, under conditions when the fish pond is receiving daily applications of mineral fertilisers, or where fish ponds are highly productive with very fertile soil naturally-enriched with nutrient minerals and carbonates, or fish ponds with nutrient-rich waters resulting in a high concentration of algalbased detrital organic matter (Schroeder et al., 1990).

Fish Species and Animal Stocking Rates

Conservatively, 5 tons of tilapia/ha/year is attainable for integration with 150 pigs. Higher yields of about 15 tons/ha/yr of the air-breathing silver-striped catfish can be expected from integration with about 300 pigs. However, lower yields of carps (less than 5 t/ha year) should be expected and they should be integrated with fewer pigs since carps are more sensitive to low levels of dissolved oxygen than tilapia (Edwards, 1985).

Intensification of Management Inputs

Yields of fish in integrated farming systems can be considerably increased through intensification involving an increase in stocking density of fish, supplementary energy-rich fish feed (cereal or rice bran and complete pelleted feed) and aeration of pond water.

A 5 tons of tilapia/ha/year is a conservative fish production figure for integration with 150 pigs in Thailand. Higher tilapia yields of 15 tons/ha/year have been reported for integrated systems with pigs but with the fish also fed soyabean cake and rice bran and pelleted feed for the last 2 months of growth, and the pond aerated with several paddle-wheels.

WAYS TO INTENSIFY FISH PRODUCTION IN INTEGRATED FARMING SYSTEM

It is possible to intensify fish production further by the addition of an energy-rich feed such as cereal or rice bran, and still further by adding complete pelleted feed (Figure 2). To ensure increased fish yields with increased levels of feed, it may be necessary to increase the number of fish stocked in the pond. Dissolved oxygen levels may fall to low levels with intensification, so it may be necessary to aerate the water with a mechanical aerator. Yields of 1.5 – 4.7 tons/ha/year were reported from commercial duck/fish integrated farms in Hong Kong; besides duck manure and spilled duck feed, the fish were fed corn meal, rice or wheat bran, oil cakes and bean fragments. Much higher yields were reported from commercial farms in Taiwan where the fish were fed rice bran and soybean cake : A moderately-low production of 7.4–8.7 tons/ha/year were increased to 13.5–18.0 t/ha/year when the fish stocking density was increased, when the fish were fed pelleted feed during the last two months of the culture period, and when water was aerated by several sets of paddle wheels.

Another method of intensification of fish production is by stocking a higher initial fish biomass and by intermediate harvesting when the fish growth curve starts to slow down. Such a management strategy should lead to a considerably higher cumulative fish yield. Some integrated duck/fish farms in Hong Kong produce two or more crops of fish each year by initially stocking fish of different sizes, followed by repeated harvesting and stocking (Sin, 1980). Such method to intensify fish production is by manipulation of the fish stock to avoid both the initial slow rate of increase of the fish biomass (due to a low initial fish biomass) and the final slow rate of increase of fish biomass (due to the fish biomass approaching the carrying capacity or maximum biomass of fish that the pond can support under a given set of environmental conditions).

	Figure 1. The relationship between fish stocking density and fish yield as a function of various types of pond nutritional inputs. Modified after Van der Lingen (1957), cited by Hickling, 1962.
	Figure 2. Upper graph normal rate of increase of a fish population. Lower graph, a higher initial stocking and intermediate harvesting to avoid the initial and final slow periods of increase in weight, respectively.

CONCLUSIONS

In integrated livestock-fish farming, the animal manure from the livestock properly applied could lead to a considerable increase in fish production. The use of animal manure to boost fish production is viable.

The significant additional profit with the integration of livestock is especially due to reduced feed costs to the fish as well as extra revenue from the sale of birds/animals.

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Table 1. Fish production (tonnes/ha/year) in integrated farming systems.

* European common carp Cyprinus carpio L.; Chinese silver carb Hypophthalmichthys molitrix V.; grass carp Ctenopharyngodon idella V.; bighead carp Aristichthys nobilis Richardson
# hardy and air-breathing species such as snake-skin gouramy Trichogaster pectoralis Regan, 3-spot goramy Trichogaster trichopterus Pallas, catfish Clarias batrachus Linnaeus, snakehead Ophicephalus striatus Bloch, climbing perch Anabas testudineus Bloch, Notopterus notopterus Pallas and Aplocheilus panchax Hamilton
** Silver carp, bighead carp, grass carp, common carp Cyprinus carpio, bream Megalobrama amblycephala, crucian carp Carassius auratus, and Distoechodon tumirostris
## Prevention of fish disease includes reservoir clearing with quicklime (750–1125 kg/ha), fingerlings disinfection and self-supply of fingerlings, regular application of chemicals, implementation of “four feeding principles” (e.g. fixed feeding time, place, quantity and quality) and fermentation of animal manure.