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Joselito R. Somga1, Sonia S. Somga1 and Melba B. Reantaso1,2

1Fish Health Section, Bureau of Fisheries and Aquatic Resources,
860 Arcadia Bldg., Quezon Avenue
Quezon City, 1103 Philippines

2Network of Aquaculture Centres in Asia-Pacific
PO Box 1040, Kasetsart Post Office
Bangkok 10903, Thailand

Somga, J.R., S.S. Somga and M.B. Reantaso. 2002. Impacts of disease on small-scale grouper culture in the Philippines. p. 207-214. In: J.R. Arthur, M.J. Phillips, R.P. Subasinghe, M.B. Reantaso and I.H. MacRae. (eds.) Primary Aquatic Animal Health Care in Rural, Small-scale, Aquaculture Development. FAO Fish. Tech. Pap. No. 406.


A farm-level participatory survey of the impacts of disease in small-scale grouper (Epinephelus spp.) culture in the Philippines was conducted from July to September 1999. A total of 72 fish farmers and one co-operative with a membership of 65 families engaged in small-scale fish production from Cavite and Capiz provinces in Luzon and the Visayas Islands, respectively, were interviewed. Grouper culture is carried out in pens and cages along coastal bays and adjoining tributaries. It contributes significantly to local livelihoods, particularly of those carrying out small-scale fishing activities as the main source of income. It requires low capital investment (as little as US$250, 1 US$=39 Pesos) with potentially high returns. Being an export commodity, live grouper commands a good market price of US$7-11/kg, similar to the price of shrimp. Grouper seed, from natural sources, are either purchased from traders or caught by the farmers themselves. The culture period ranges from 6-12 months, depending on the size of fry or fingerlings at stocking.

Fish farmers recognise health problems as a significant constraint to grouper culture. Unidentified diseases exhibiting a range of clinical signs such as ulceration, fin rot, tail rot, scale loss, white spots, haemorrhages and cataract; leech parasitism; or a combination of these abnormalities were found to cause high mortalities, especially among fry. Proliferation of grouper and milkfish pens and cages, oyster and mussel farming, unstable climatic conditions and run-off following heavy rains contributed to the deterioration of the quality of the aquatic environment, which is believed to be associated with the problems reported. For beginners, the lack of proper husbandry knowledge intensified existing problems. An inadequate supply of fry was another important constraint identified by farmers.

Farmers experiencing large losses due to disease temporarily cease operations and resume production when they acquire sufficient capital. Other species, such as snapper (Lutjanus sp.), seabass (Lates calcarifer), and milkfish (Chanos chanos), are also cultured in the majority of farms; however, they are not considered good alternative species. Although these species are quite resistant to the diseases affecting grouper, they have a low market value. Even though disease poses a high risk to grouper culture, farmers are not discouraged from continuing this activity, as they believe that the high market price of grouper will contribute to the advancement of their household status.


In 1998, aquaculture production in the Philippines was 954,000 mt, valued at 26.2 billion Philippines pesos (PHP) (US$671.79 million) and contributing 34.2% to the total fisheries production. There are about 258,480 Filipinos engaged in aquaculture activities, about 26% of the total number of people employed in the entire fishery sector (aquaculture, municipal and commerical fisheries activities) (Philippine Fisheries Profile 1998). In 1997, total fish production from marine fish cages, pens and brackishwater ponds was 199,349 mt valued at PHP 2,176,481,300 (US$55.8 million) (BAS 1997).

Grouper (Epinephelus spp.) is the most popular marine finfish species cultured because it adapts easily to different culture conditions (pond, cage and pen) and has a high growth rate. Grouper, particularly live, commands a high market price in both local and foreign markets, especially among Chinese communities. The average price per kilo is about US$7-11, which is almost the same as the price of shrimp. In 1997, total grouper production in ponds, cages and pens was 496 mt, valued at PHP 184,388,000 (US$4.7 million) (BAS 1997).

The industry depends on seasonal wild-caught seed. The orange-spotted grouper (Epinephelus coioides) and the Malabar grouper (E. malabaricus) are the two commonly cultured species, the former being the most commonly cultured. The culture period ranges from six to twelve months, depending on the size of fry and fingerlings at stocking. Market size is about 0.4-1 kg, and trash fish is commonly used for feeding.

The majority of grouper cage and pen operators are smallholders for whom the primary source of income is fishing. They mostly reside in coastal areas and have no stable daily income. Culturing grouper can reduce poverty and improve their livelihood, as it requires low capital investment and has potential for high returns.

There are several reports of disease and health-related problems affecting grouper (Baliao et al. 1998, Leong 1994, Chong and Chao 1986). Significant mortalities of grouper are also experienced in the Philippines. Laboratory examinations based on diagnostic cases received, as well as on samples collected for the research project on grouper health undertaken by the Philippine Bureau of Fisheries and Aquatic Resources (BFAR), showed consistent isolation of Vibrio spp. in the affected fish and the presence monogenetic trematodes on the gills.

This survey was conducted to determine the impacts of health problems in small-scale grouper culture in the Philippines. Its specific objectives were: 1) to determine the current understanding of small-scale grouper farmers of the concepts of fish disease, aquatic animal health and health management; 2) to assess the socio-economic impacts of diseases and other health-related problems on the livelihoods of small-scale grouper farmers; and 3) to identify health management strategies used in small-scale grouper culture systems.


A farm-level survey was conducted from July to September 1999 using a semi-structured questionnaire developed by the Network of Aquaculture Centres in Asia-Pacific (NACA). It consisted of two parts. The first part contained questions on: a) general account of the farm; b) description of operation; c) revenue; d) cost of production; e) household activities; f) general disease problems, recognition of diseases and related losses, action taken and received, and social perception of the effect of problems. The second part related to specific diseases that had been encountered.

A total of 72 fishfarmers and one co-operative (with 65 member families) engaging in small-scale fish production in the provinces of Cavite and Capiz were visited and interviewed. The areas visited were: Cavite City, Cavite (n=29); Cagay, Roxas City, Capiz (n=3 + 1 c-ooperative); Barra, Roxas City, Capiz (n=12); and, Basiao, Ivisan (n= 28). The information gathered was collated and tallied manually and data are presented as percentages.


Description of Grouper Culture Operation

Small-scale grouper culture uses cage and pen systems. They are located along coastal bays and adjoining tributaries. The usual size of cage is 3x3x3 m, whereas, with pens, there is no standard size. Of the farmers interviewed, 18.0% started grouper farming between 1980-1990. There was a significant increase to 81.9% between 1991-1995. The culture cycle runs from 6-12 months, depending on the size of fry and fingerlings at stocking. Market size ranges from 0.4-1 kg, with a market value (live) of US$7-11/kg. Seed from natural sources is either purchased from traders or caught by the farmers themselves, and ranges in price from US$0.12-1.53/fish.

Aside from grouper, fish farmers also catch and raise other marine fish species such as snapper, Lutjanus spp. (45.8%); seabass, Lates calcarifer (16.7%); milkfish, Chanos chanos (6.9%) and others (e.g., siganids and porgy). Trash fish are also used as feed.

Household Status

The majority of the fish farmers interviewed earn much less than the Philippine minimum wage of US$129.00/month (Table 1). Most farmers (70.8%) rely on fishing activities to support their families, while others are involved in labouring and small business (e.g., mini store, livestock) activities. Farmers culture grouper as a source of income (100%). Some considered other cultured species for food (30.6%). Fish culture makes a significant contribution to their income (Table 2). The operating costs vary depending on the number and size of cages and pens. Some farmers started grouper culture with a capital investment of less than US$100.00 (Table 3).

Table 1. Annual household income of surveyed grouper farmers in 1998.1

Fish culture is usually managed by the husband (96.6%) or wife (1.4%); some (11.1%) use hired labourers. Feeding, cleaning of cages or pens and fry purchasing are performed by the husbands. Two to five hours per day are usually spent on the farm; however, some farmers may spend more than ten hours, staying overnight to protect their stocks from theft. Wives provide assistance during harvest and in marketing the fish. Farmers learned to raise fish by themselves (76.4%) or from other fish farmers, neighbours and friends (16.7%). Only a few (6.9%) learned to raise fish from governmental and non-governmental organisations.

Table 2. Contribution of aquaculture to household income.

Table 3. Operating cost during the last culture period.

Disease Problems

The farmers experience several diseases and considered the first two months of the culture period to be critical. Common problems encountered by farmers are summarised in Table 4, and discussed below:

White spots, eroded caudal fin, fin and tail rot

This problem is common during the first two months of the culture period and mortalities may reach 70%. Farmers use freshwater (rainwater) bath as a treatment. A very few farmers also use betadyne and formalin. Treatment is not always successful.

Leech infestation

Leeches are prevalent between the months of February and September in both the nursery and grow-out stages. Higher prevalences are observed in farms with no regular cleaning of net cages. Affected fish at all stages show pale discoloration, weakness and inappetence. Leech infestation may result in 100% mortality within a short period of time. The problem is managed by the manual removal of leeches and the cleaning of net cages. For treatment, jackfruit peel, hung in the water along the sides of net cages is used. Farmers believe that the strong odour of jackfruit peel dislodges and eliminates the leeches.

Table 4. Summary of health problems encountered in grouper farming.

Ulceration, red spots with tail and fin rot

This problem is common during the grow-out stage. The condition is chronic and mortalities may range from 10-35%. There is no seasonal pattern to its occurrence. A freshwater (rainwater) bath is commonly used to treat the fish. Application of betadyne and formalin is also commonly used. Some fish with early signs of the disease may respond to treatment. Some farmers have tried guava and madre cacao leaf extracts without success.

Exophthalmia, cataract

This disease is observed at grow-out stage; however, it is not considered as a serious problem. Mortalities related to this condition are less than 5%. No treatment is being applied.

Ruptured gallbladder

The problem is acute and the fish do not show any external lesions. Sudden mortalities are observed, and farmers assume that the affected fish did not survive because the gall bladder is ruptured. This problem is experienced during January to February; no treatment is applied.

Mortalities without gross lesions

Nursery and grow-out stages are both affected with this problem. This is an acute condition and mortalities may reach 100%.


A few farmers are affected by flooding. Strong water currents and flash floods can destroy the net cages and allow fish to escape. Farmers also anticipate thefts, and dogs are used to guard the farm. The owner or hired labourer may also stay on the farm during the night.

When farmers experience disease problems, a very few (8.3%) contact fry traders and local government for assistance. Most (91%) of the respondents did not contact the government because of the perception that small-scale farmers are not given particular attention. Information on fish health is mainly provided by other farmers who are usually neighbours and friends.

Survival rates (%) are presented in Table 5.

Table 5. Survival rate of grouper during the last culture operation

Causes of Disease Problems

Several factors are believed to contribute to the disease problems encountered by fish farmers. These include (a) unstable conditions brought about by sudden changes in weather, such as heavy rain after a long dry season; (b) run-off of domestic and industrial waste following heavy rain; (c) deteriorating water quality due to increased aquaculture activities, such as grouper and milkfish pen and cage culture, and oyster and mussel farming; (d) lack of technical knowledge relating to proper husbandry and health management, particularly for beginners; and (e) lack of desire among farmers to contact appropriate governmental agencies.

Socio-economic Impacts of Health and Disease Problems

Disease problems significantly affect the livelihoods of the fish farmers. The majority (75%) of farmers experienced reduction in income, while some (19.4%) increased their debt, particularly those who borrowed to invest in aquaculture. Culture operations were also prolonged because of the time needed for the affected fish to recover from disease.

Although disease problems are recognised as significant constraints to grouper culture, 87.5% of respondents did not change their attitude towards grouper farming. A small percentage, particularly those that experienced large losses, temporarily stopped culturing grouper (9.7%), while some changed culture species (2.8%). Farmers usually resumed operations once they had acquired sufficient capital. Other fish species cultured by the majority of the farms surveyed were not considered as good alternatives. Although these species seemed to be resistant to the disease problems affecting grouper, they have a lower market value.

Although disease poses a high risk to grouper culture, fish farmers are not discouraged and continue operating because they believe that it is still very profitable. They are optimistic that this activity will contribute greatly to the enhancement of their household status.


Grouper culture is a promising industry, particularly for small-scale fish farmers. It has huge potential to make a significant contribution to the household income of these farming communities, and the farmers are very keen to further develop it. To make the industry sustainable, the following strategies are strongly recommended:

  • Development of policies for the regulation of aquaculture activities and strict enforcement of associated laws. In the areas surveyed, there were no designated sites for aquaculture and no regulations stipulating the maximum permitted number of cages or pens for the culture of grouper and other fish species, nor any regulation of other aquaculture (e.g., oyster and mussel farming) activities. This unregulated establishment resulted in overcrowded conditions. The Philippines Fisheries Code of 1998 (RA 8550), Article III, Section 51, states that "fish pens, fish cages, fish traps and other structures for culture of fish and other fishery products shall be constructed and shall operate only within established zones duly designated by Local Government Units (LGUs) in consultation with the Fisheries Aquatic Resources Management Councils (FARMCs) concerned consistent with the national fisheries policies." If the provisions in this code could be duly implemented, it would significantly reduce the deterioration of the environment and the stress that results from crowded conditions.

  • Training on grouper culture, including proper husbandry and health management, is required. Most farmers, particularly new entrants, have inadequate technical knowledge on proper fish culture, husbandry and health management. Training on these subjects will help them to understand the concept and principles of sustainable fish farming. Through training, they will be equipped with sufficient scientific knowledge to realise the consequences of improper fish culture, husbandry and health management and the impact on productivity and the aquatic environment.

  • Strengthening of technical assistance and extension services to farmers is required. There should be strong linkages between the government extension workers and the small-scale fish farmers. This should be enhanced through regular farm visits and consultation. Monitoring of the health status of grouper farms should be carried out regularly. Extension workers should be more active and ensure that they respond to the needs of the farmers. They should be encouraged to report problems immediately in order to ensure appropriate technical services and guidance.

  • Research on significant disease problems and formulation of preventative and control strategies is required. Research should be problem solving and focused on the needs at the farm level. The farmers should participate in developing research plans. Short-term studies should provide immediate practical application of results to address significant issues.


The survey was funded by the Bureau of Fisheries and Aquatic Resources (BFAR) under the research project on Health Management of Grouper in the Philippines. The authors would like to thank the provincial and municipal agricultural officers of Cavite City, Cavite and Roxas City and Ivisan, Capiz, for their assistance during the survey. We would also like to thank the organising committee of the FAO/NACA/DFID/Government of Bangladesh-sponsored workshop on "Primary Aquatic Animal Health Care in Small Scale Aquaculture," held in Dhaka from 27 to 30 September 1999, for travel support to the senior author to attend and present this paper at the workshop.


Baliao, D.D., M.A. de los Santos, E.M. Rodriguez and R.B. Ticar. 1998. Grouper Culture in Brackish Water Ponds. Aquaculture Department, South East Asian Fisheries Development Center, Tigbauan, Iloilo, Philippines, 17 p.

Bureau of Agricultural Statistics (BAS). 1997 Fisheries Statistics of the Philippines. Department of Agriculture. Quezon Avenue, Quezon City, Philippines, 103 p.

Chong, Y.C., and T.M. Chao. 1986. Common Diseases of Marine Foodfish. Primary Production Department, Ministry of National Development, Republic of Singapore, 34 p.

Leong, T.S. 1994. Parasites and Diseases of Cultured Marine Finfishes in South East Asia. School of Biological Sciences, Universiti Sains Malaysia, Pulau Pinang, Malaysia, 25 p.

Philippine Fisheries Profile. 1998. Bureau of Fisheries and Aquatic Resources. Department of Agriculture. Quezon Avenue, Quezon City, Philippines, 52 p.

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