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FISH PARASITES IN INTEGRATED FARMING SYSTEMS IN PENINSULAR MALAYSIA

Lim L. H. S.
Institute for Advanced Studies,
University of Malaya, Kuala Lumpur
Malaysia

ABSTRACT

Fish parasites have been shown to cause mortalities under cultured system which tend to enhance parasitim. Even if these parasites do not cause death directly, they tend to lower the general health of the fish making them more susceptible to other more dangerous pathogens. A literature review indicates that there is a lack of information on fish parasites in such systems. The lack of information is not restricted to this system alone; there is a general paucity of parasitological investigations in Peninsular Malaysia. Despite the increased interest in fish Parasitology in the 1980s there is still no intensive work on Parasites of fish cultured in integrated systems. Only rice-field fishes have been investigated and it most cases these investigations are done for specific groups of parasites.

INTRODUCTION

The main objective in integrated systems is to enhance production by maximizing output through utilizing all available nutrients within a system without any wastage (complete nutrient cycling within an ecosystem). Fish is a necessary component in the aquatic phase of integrated systems serving not only as food for the farmers but also as harvesters of primary and secondary productions in the systems. The fish also function as hosts to a wide spectrum of parasites and as intermediate hosts to a number of parasites of man (see later) and animals.

In aquaculture the health of fish is of utmost importance. The health of fish can be affected by environmental factors, nutrition as well as by pathogens (see later). The presence of a large population of a particular species of fish provides ample habitats for parasites and the stress conditions associated with such crowding will also affect the health and subsequent susceptibility of the fish to parasites. Parasites are important in that they affect the productivity of the fish in the systems through mortalities, by decreasing growth rate, reducing the quality of the meat and making the hosts more susceptible to more pathogenic parasites.

The fish species in integrated farming systems depend on the types of integrated systems involved. The usual integrated fish farming systems include:

Pig-vegetable-fish farms

Fishes here are usually farmed for family consumption although some are sold. The fishes introduced traditionally into such system include Ctenopharygnodon idella Valenciennes, Aristichthys nobilis Richardson and Cyrpinus carpio Linnaeus. However such systems are on the decline because of strict laws governing the discharge of pig-wastes into water bodies.

Poultry-Vegetable-fish farms

Fish are again introduced into this system. Besides the species used traditionally, other species have been introduced. These include tilapia, Pangasius sutchi Fowler, Leptobarbus hoevenii Bleeker and a hybrid of Clarias macrocephalus Gunther and C. gariepinus Burchell, the African catfish. Some of these farms are found in disuse mining areas where there is a ready supply of water in tin-mining pools. Usually such systems are free from chemical pollutants but the introduction and the indiscriminate use of pesticides, herbicides and organic fertilizers on the vegetable plots may result in contaminated fishes.

Rice-fish systems

Fishes (Anabas testudineus Bloch, Ophicephalus striatus Bloch, Clarias batrachus Linnaeus, C. macrocephalus Gunther and Trichogaster trichopterus Pallas and T. pectoralis Regan) in this system are brought in by the irrigation systems. So far there is no effort to introduce fishes on a large scale into such systems although there are attempts by certain farmers to culture these fishes in ponds around their houses. This may be a better way to culture fish in view of the vast amount of pesticides and herbicides input into rice-field systems. The amount of herbicide and pesticide residuals in rice-field fishes are high (Meier et al., 1983). This aspect should be investigated to determine the effects of these chemicals on fish and whether fish grown under such conditions are safe for human consumption. A possible use of rice-field system is to grow aquarium fishes.

LITERATURE REVIEW OF FISH PARASITOLOGY IN INTEGRATED SYSTEMS

There is a paucity of knowledge in fish parasitology in the different types of aquatic habitats in Peninsular Malaysia (Lim, in preparation) and the same is true in integrated systems. There have been some studies on parasites on cultured fishes in Peninsular Malaysia (Lim, in preparation). However, it is not possible to glimpse from the literature whether a particular culture system studied is an integrated system or not since this is not usually mentioned. However integrated systems are not the usual form of aquaculture practices in large commercial scale because the eutrophicated environment usually reduces the environmental carrying capacity making commercial fish growing uneconomical. In Peninsular Malaysia integrated farming systems are used by rural farmers to maximise farm outputs on a substitence level.

So far only fishes from rice-fields have been extensively studied in terms of parasitology (Zaman, 1987; Lim, 1987; Table 1). However many of these studies are not intensive studies but surveys for only specific group of parasites (Lim, 1987). There are few attempts to study the total parasitofauna in rice-field (Zaman, 1985). Parasitological investigations are usually disconnected and so far there have been no studies which are concerned with the total parasitofauna (Furtado & Tan, 1973; Leong & Mokhat, 1981; Zaman, 1985; Lim, 1987).

POSSIBLE EFFECTS OF ENVIRONMENT ON FISH HEALTH

The parasite community in any ecosystem (see Figure 1) is affected by host availability, host characteristic (such as age) and behavioral patterns, availability of intermediate hosts, and physico-chemical characteristics of the waters.

There is a paucity of information on the effects of water quality on the biology (development) and ecology of parasites in tropical systems. Such knowledge will enable us to control parasites by manipulating environmental parameters to reduce parasitic infections within an ecosystem. Ecological information on tropical fish parasitology is also limited (Lim, 1987) and the same is true for such information on integrated systems (Zaman, 1985).

The characteristics of the water in some integrated systems have been studied (see Mukherjee et al., this volume). However there is a lack of published information on the fauna present in integrated systems, except probably for rice-fields fauna (Heckman, 1979; Richard Lim, pers. comm.). These fauna are important as fish food as well as intermediate hosts to a variety of fish parasites.

As already noted the effects of water quality on the host fauna and their parasites in the integrated systems have not been documented. The possible effects on parasites however could be speculated upon based on ecological information known from other systems (Kennedy, 1976; Dogiel, 1962; Esch, 1977). Parasites are effected by both the macro-and micro-environments. The environmental factors are important in the recruitment, transmission, colonization, fecundity and survival of both the adult and larval parasites (Esch, et al., 1977).

Water quality can effect the fish directly (through deoxygenation in the nutrient-rich waters especially from dusk to dawn), or indirectly through the blooms of algae Phang this volume). The enrichment of the water will result in an increase in productivity in the zoo - and phyto-plankton communities, as well as in the mollusc, insects, frogs and fish communities. These organisms serve as food to the fish and may also function as intermediate hosts to parasites of fish. Water quality also affects the presence of certain groups of organisms which function as primary intermediate hosts to parasites which use fish as intermediate hosts. Many of these parasites are of medical and veterinary importance (see later).

Table 1. Summary of the parasitological studies on fish species which are usually found in integrated systems.

Figure 1. A schematic model showing the relationship between inherent host accetability factors and external environmental factors in regulating parasite input and output at the infrapopulation and surpopulation levels (Esch, et al., 1975) in a given micro-environment.

FISH AS INTERMEDIATE HOSTS TO HUMAN PARASITES

Fish have been shown to act as intermediate host to at least 4 trematodes (Clonorchis, Opthisthorcis, Heterophis and Metagonimus spp.) and 2 nematodes (Gnathosoma sp. and Capillaria phillipinensis) in Southeast Asia which can be transmitted to man via eating raw or insufficiently cooked fish (Ramalingam, 1987; Sornamani, 1987). Fish also functions as intermediate hosts to parasites of other animals (Table 2).

The translocation of fish together with the presence of potential intermediate hosts and tourist trade may result in the transfer of parasites of man such as Diphyllobothrium latum Luhe, 1910 to Southeast Asia although this disease is a temperate disease.

In all cases man is probably not the true final host and the parasites are transmitted via uncooked fish meat. The trematodes that infect man required a gastropod as obligatory first intermediate hosts. The environment created by the integrated farming systems may be conducive to snails which may increase the incidence of such infections in man. For example Bithynia siamensis goniomphales Morelet, the first intermediate hosts of the human liver fluke (Opisthorchus tenuicollis Stilas & Hassal), are found in great abundance in Thailand with fish being the second intermediate hosts (Heckman, 1979).

RECOMMENDATIONS

The study of fish parasites in integrated systems is important because parasites have been shown to lower fish productivity, decrease fish health making them more susceptible to diseases and even cause mortalities in fish. This will result in loss of economic returns and loss of protein sources.

One of the objectives of this presentation is to identify research priorities in parasitological investigation in integrated farming systems. This is especially important since integrated systems are used by the rural farmers to supplement both their protein intake and economic earnings.

The paucity of study of parasites in integrated farming makes the identification and documentation of the parasites in relation to physico-chemical parameters a priority. The biology and ecology of fish parasites should also be investigated in integrated systems to determine the effects of water quality on these characteristics. An investigation should also be done simultaneously to document the fauna of integrated systems to see whether there are any potential intermediate hosts to human parasites as well as fish parasites.

A thorough parasitological investigation in the integrated systems will enable the formulation of an effective disease management programme which will in turn maximise the productivity of the system.

There is a need to ensure that the water in integrated systems is safe before culturing any organisms for human or animal consumption because of the intensive use of agrochemicals. In the rice-filed integrated system the use of pesticides and herbicides in combination with the shorter growing seasons have resulted in a decrease in fish catches note in large rice growing schemes. However before encouraging the poduction of fish in such system, a toxicological study should be conducted to look into the levels of chemicals in the water, the sediments and the fish.

It is also important to examine the other fish species available which are considered to be noneconomical because they function either as carrier hosts or reservoir host and at the same time are important part of the food-chain. There are several ecological hypotheses regarding the parasites that should be considered in fish farming. Polyculture should be encourage; since most parasites are very host specific there will be little chances of parasite transfer between host species. However one must also take in consideration the parasites with broad specificity (Lim, 1987). Closely related species may possess same type of parasites (Lim, 1987; Zaman, 1985; Dogiel, 1962).

Therefore, to summarise it is recommended that a total ecological investigation into integrated farming systems be done. This holistic approach is necessary to reveal the effects of each component within the integrated farming ecosystems on the health of the ecosystems especially that of the fish and the human consumers.

Table 2. Helminths of medical and veterinary importance (extracted from Reichendback-Klinke and Elkan, 1965; Piekarski, 1962; and Bauer, 1958) (see Lim, 1979).

REFERENCES

Dogiel V.A. (1962). General Parasitology. English translation by Kabata Z. Published by Oliver and Boyd. 516 pp.

Esch G. W. (1977). Regulation of parasite polutions (ed). Academic Press. 253 pp.

Esch G. W., Hazen T.C. & Aho. J. M. (1977). Parasitism and r- and K-selection. pp. 9–62. In: Regulation of parasite populations. Esch G. W. (ed). Academic Press. 253 pp.

Fernando C. H. Furtado J. I. (1963). Helminth parasites of some Malayan Freshwater fishes. Bull. Natl. Mus. Singapore, 32: 45–71.

Furtado J. I. (1961). A note on intestinal parasites in some Chinese carps. Malay. Agricult. J. 43: 232–242.

Furtado J. I. and Lau C. L. (1968). Orientocreadiidae) from a Malayan catfish Clarias batrachus Linaeus Fed. Mus. J. 13: 124–132.

Furtado J. I. (1963). A new caryophyllaeid cestode, Lytocestus parvulus sp. nov., from a Malayan catfish. Ann. Mag. Nat. Hist. 6: 97–106.

Furtado J. I. & Tan K. L. (1973). Incidence of some helminth parasites in the Malaysian catfish, Clarias Batrachus (L.). Verh. Internat. Verein. Limnol. 18: 1674–1685.

Hanek G. and Furtado J. I. (1973). Gyrodactylus fernandoi sp. n. (Monogenea: Gyrodactylidae) from Clarias batrachus L. in Malaysia. Zool. Anz. 191; 196-198.

Heckman C. W. (1979). Rice field ecology in Northeastern Thailand. The effect of wet and dry seasons on a cultivated aquatic ecosystem. Monographiae Biologicae 34. Dr. W. Junk Publishers. 228 pp.

Kennedy C. R. (1976). Ecological Aspects of Parasitology (eds.). North Holland Publishing Company 473 pp.

Leong T. S. and Mokthar A. S. (1981). Parasites freshwater fish from Alor Star and Sungai Petani fish markets, Kedah. Malay. Nat. J. 34: 135–140.

Lim L. H. S. (1979). Monogenea and Digenea of freshwater fishes mainly from Tasek Bera, Malaysia. Unpublished M. Sc. theses, University of Malaya, Kuala Lumpur.

Lim L. H. S. (1986). New species of Trianchoratus Price and Berry, 1966 (Ancyrocephalidae) from Malaysian anabantoid and ophicephalid fishes. Parasitol. Hung. 19: 31–42.

Lim L. H. S. (1987). Distribution and diversity of monogeneans in freshwater fishes of Penisular Malaysia. Unpublished Ph. D. thesis of the University of Malaya, Kuala Lumpur.

Lim L. H. S. (1990a). Silurodiscoides Gussev, 1961 (monogenea: Ancyrocephalidae) from Pangasius sutchi Flowler, 1931 (Pangasiidae) cultured in Penisular Malaysia. Raffles Bull. Zool. 38: 55–63.

Lim L. H. S. (1990b). Freshwater monogeneans of Penisular Malaysia. Asian Fish. Sci. 3: 275–285.

Lim L. H. S. (1991). Three new species of Bychowskyella Achmerow, 1952 (Monogenea) from Penisular Malaysia. Systematic Parasitology 19: 33–41.

Lim L. H. S. (1991). Fish parasitology in Malaysia. Paper presented at the regional seminar on Ecology and conservation of Southeast Asian marine and freshwater envirnments including wetlands. Institute for Advanced Studies, University of Malaya, Kuala Lumpur. 4–6 Nov. 1991.

Lim L. H. S. and Furtado J. I. (1983). Ancylodiscoidins (Monogena: Dactylogyridae) from two freshwater fish species of Peninsular Malaysia. folia Parasitol. 30: 377–380.

Meier, P. G., Fook, D.C and Lagler, K. F. (1983). Organochlorine pesticide residues in rice paddies in Malaysia, 1981. Bull. Environ. Contam. Toxicol 30: 351–357.

Ramalingam S. (1987). Aquatic vectors and intermediate hosts of diseases. In: Sustainable Clean Water. Arch. Hydrobiol. Ergebn. Limnol. 28: 371–380, Lim R. P., Viner A. B., Lim l. H. S. & Furtado J.I. (eds.)

Sornmani S. (1987). Health problems of water borne diseases in relation to water resource development projects in southeast Asia. In: Sustainable Clean Water. Arch. Hydrobiol. Ergeben. Limnol. 28: 361-370, Lim R. P., Viner A. B., Lim l. H. S. & Furtado J. I. (eds.)

Zaman Z. (1985). Parasite fauna of paddy field catfish (genus Clarias) from Kedah and Perak, Peninsular Malaysia. Unpublished Ph. D. thesis. Universiti Sains Malaysia, Pulau Pinang.