The use of chemotherapeutic agents in aquaculture in the Philippines

Chemotherapeutants are widely used to treat diseases of fish, specifically shrimp and aquarium fishes in the Philippines. The most commonly treated diseases are luminous vibriosis, filamentous bacterial disease, shell disease, larval mycosis and protozoan infections in shrimp and white spot, velvet disease, fin and tail rot, crustacean and monogenean infections, fungal infections and dropsy in finfishes. These chemicals include chloramphenicol, erythromycin, oxytetracycline, nitrofurans, formalin, malachite green, potassium permanganate, copper sulfate and Neguvon. The indiscriminate use may cause mortalities and morphological deformities in the host, development of resistant strains of bacteria and public health hazards. The Philippine government has embarked on regulating the use of these chemicals. Initially, use of chloramphenicol has been banned in food producing animals. In the near future, rules and regulations on the registration and labelling of these chemicals will be implemented. While these are a welcome development, much still needs to be done. It is recommended that medically important drugs be excluded from aquaculture. The campaign on the careful and restricted use of drugs should be intensified in both drug and aquaculture industries. Further research must be done on the screening of other drugs which are effective and environmentally safe. Lastly, funds should be allocated for research, extension and manpower development in fish health management, specifically, in chemotherapy

Integration of finfish in shrimp (Penaeus monodon) culture: an effective disease prevention strategy

A farm trial on integration of finfish (i.e., tilapia) in shrimp (Penaeus monodon) culture was conducted in Negros Occidental, Philippines to prevent luminous vibriosis in shrimp. The farm engaged in shrimp monoculture from 1987 to 1995. However, the prevailing luminous vibriosis outbreaks that started in 1994 prompted the farm operator to shift to tilapia culture in 1995-1996. The farm resumed shrimp operations in 1996 but by this time tilapia had already been integrated in the culture system. This paper reports on the results of the trial for 1999 using three ponds (ponds 7, 9, 29). These ponds had previously been used for tilapia culture for two years. During shrimp culture, they drew water from reservoirs stocked with tilapia and within the shrimp ponds tilapia are also stocked inside cages. This technology integrates crop rotation, biological pretreatment and polyculture into one system. During the culture period the chemical and bacteriological quality of soil, water and shrimp were monitored. Water quality parameters were within normal ranges for shrimp culture. Luminous bacterial counts in water and shrimp were consistently below 10 colony forming units (cfu)/ml and 103 cfu/hepatopancreas (hp), respectively. These levels are below threshold levels associated with luminous vibriosis outbreaks. With a stocking density of 19.43 shrimp postlarvae (PL)/m2, pond 7 yielded 2,605 kg shrimp/ha with an estimated survival of 35.65% after 109 days of culture (DOC). With a stocking density of 18.69 PL/ m2, pond 9 yielded 5,472 kg shrimp/ha with survival of 100% after 148 DOC. With a stocking density of 19.33 PL/m2, Pond 29 yielded 5,702 kg shrimp/ha with survival of 82.66% after 151 DOC. The relatively low production in pond 7 can be attributed to the inferior quality of the batch of stocked shrimp PL that already had a low survival of 50% at DOC 30. Comparing the production performance from this present trial with that of this and other farms before the 1994 outbreaks, these good results cannot simply be attributed to chance despite of the lack of control in this farm trial. These results are consistent with the results of a previous trial of the same farm, the ongoing verification trials in Negros Occidental, and the observations of many farmers in other parts of the country on the potential of shrimp-finfish integration in preventing luminous vibriosis in shrimp