Farmer perceptions of fish health management and biosecurity on grouper farms in Bali, Indonesia

A socio-economic survey was undertaken for sea-cage farms in northern Bali, Indonesia, to better understand farmer attitudes with respect to fish health and biosecurity.  The survey used a formal questionnaire that was administered to farm owners or managers.  A total of 14 sea cage farms were randomly selected from a pool of 38 sea cage farms in northern Bali.

The main species farmed at the time of the survey were tiger grouper Epinephelus fuscoguttatus, the hybrid grouper 'cantang' ♀ E. fuscoguttatus × ♂ Epinephelus lanceolatus, and hybrid grouper 'cantik' ♀ E. fuscoguttatus × ♂ Epinephelus polyphekadion.  These three species now dominate grouper production in Indonesia.  Nine farms (64%) had cultured the high-value mouse grouper (Cromileptes altivelis) within the last year.  Other species, including barramundi (Lates calcarifer) and pompano (Trachinotus spp.), were farmed in small numbers by only a few farms.

Common diseases reported by farmers are: viral nervous necrosis, iridovirus and parasite infestations.  59% of farms regarded fish losses due to disease as 'medium'; 24% as 'low', and 18% as 'high'.  No farms regarded the frequency of disease occurrence as 'low'; all regarded it as either 'medium' (57%) or 'high' (43%).

Farmer experience suggests that some grouper species are more prone to disease than others.  The grouper hybrid 'cantik' was regarded by most farmers as having a generally high propensity for disease problems, while tiger grouper was rated moderate to high.  In contrast, the hybrid grouper 'cantang' and mouse grouper were regarded as having a low propensity for disease.

Farmers ascribed disease-related losses to two main factors:

1.      Poor availability and quality of 'trash' fish feed (the main feed source used in grouper farming); and

2.      Water quality deterioration during the early part of the rainy season in November - February each year.

All 14 farms practised prophylactic treatment of the fish to reduce the incidence of disease outbreaks.  Freshwater bathing was undertaken routinely by all the sea cage farms, at intervals of 3 days to 1 week.  All the farms interviewed disinfected their equipment regularly.  However, only the larger companies (21%) separated equipment that had been in contact with infected fish, and cleaned or replaced the nets after the fish were harvested.

All the farmers interviewed were confident that they could identify disease outbreaks visually.  Swimming activity and loss of appetite were the main symptoms that farmers used to identify disease outbreaks, followed by changes in skin colour and signs of injury on the body. Formal diagnoses are rarely sought, and during disease outbreaks the farms primarily rely on the owner or technical staff to provide technical advice (93%).  Only 7% of farms consulted with government technical institutions during disease outbreaks.