IMPACTS OF DISEASE ON SMALL-SCALE GROUPER CULTURE IN
Joselito R. Somga1, Sonia S. Somga1
and Melba B. Reantaso1,2
1Fish Health Section, Bureau of Fisheries and
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
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
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.
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 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.
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.
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.
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.
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.
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