Health management in aquaculture

A textbook on diseases of cultured warmwater fish and shrimps in the Philippines. Eleven chapters cover essential information on the basic principles of disease causation, major diseases of cultured fish and crustaceans, particularly shrimps, and methods of prevention and control. Emphasis is made on major diseases that occur in the Philippines and other countries in the Asian region. Included also are topics on harmful algae, immunology and molecular biological diagnostic techniques.1st Ed

Parasitic diseases and pests

A wide variety of parasites have been identified as causing significant economic losses in fish and shrimp culture. Most of these parasites are difficult to control effectively with a single measure. The control of parasites is dependent on culture systems of the host fish, knowledge of the life cycle of the parasite, and the availability of effective treatment methods

First SEAFDEC hands-on training for important viral diseases of shrimp and marine fish

The issue on aquatic animal diseases, particularly viral diseases, in shrimp and fish is a priority because of the risks involved with the spread of diseases in aquaculture in Southeast Asia. To support existing activities on aquatic animal health in the region, the SEAFDEC Aquaculture Department and the Office International des Epizooties (OIE) organized a Seminar-Workshop on “Disease Control in Fish and Shrimp Aquaculture in Southeast Asia-Diagnosis and Husbandry Technique” which was held in Iloilo City, Philippines on 4-6 December 2001 with 60 participants from 12 countries. In the Seminar-Workshop, a networking scheme for disease diagnosis and control in the region was discussed. One of the major recommendations of the meeting was implementation of an international training course on diagnosis of viral diseases, which became the basis for the “SEAFDEC Hands-on Training for Important Viral Diseases of Shrimp and Marine Fish.

Effect of rotenone and saponin on the shell quality of juvenile tiger shrimp, Penaeus monodon

Tiger shrimp (Penaeus monodon) juveniles were exposed to varying concentrations of rotenone and saponin to determine their effects on survival and shell quality. The highest concentrations tested, 50 ppm rotenone and 100 ppm saponin, were not lethal to shrimp. Shrimps exposed to 0.001 to 50 ppm rotenone had 7.4-66.6% shell softening while shrimps exposed to 0.001 to 100 ppm saponin had 2.66-66.6% shell softening. The shell softening rates were significantly higher in 1.0 to 50 ppm rotenone and 100 ppm saponin than in control shrimps

Parasitic diseases and pests

This chapter deals with parasitic animals of significance to aquaculture because of their harmful effects on fish and crustaceans. It also illustrates the life cycle of major parasites and discusses the various methods in diagnosing diseases caused by parasites, including disease prevention and control

Toxicity of rotenone to milkfish, Chanos chanos, and tilapia, Oreochromis mossambicus

Milkfish (Chanos canos) and tilapia (Oreochromis mossambicus) were exposed to varying concentrations of rotenone (95-98% active ingredient) to determine the median lethal concentration (LC50). The 1, 6, 12, 24, and 96 h LC50 were 64, 36, 36, 30 and 25µg/1 for milkfish and 172, 123, 91, 86 and 80 µg/1 for tilapia, respectivly, at 28±1oC. In another experiment, O. mossambicus were exposed to a lethal concemtration of rotenone (100µg/1) that had been allowed to age for selected periods of time to determine whether significant degradation occurs within 24h. Mortality after 3 to 24 h exposure in 0 (no aging), 3 and 6 h aged rotenone solution were not significantly different from the control test even after 24 h of exposure. These results inducate that the treated water was no longer toxic to the fish after 12 h and acute toxicity of rotenone ceased towards the end of 12 h at 27 ± 1o

Environmental diseases

This chapter focuses on swimbladder stress syndrome and gas bubble disease, the two most common disorders due to adverse environmental conditions

The hematological changes in snakehead (Ophicephalus striatus) affected by epizootic ulcerative syndrome

Selected hematological parameters were studied in snakehead from Laguna de Bay (Philippines) affected with different stages of epizootic ulcerative syndrome (EUS). For comparison, normal (from a non-endemic area) and apparently normal fish were also studied. The hematocrit values of normal and apparently normal fish, 45.04 ± 0.71 and 47.20 ± 1.03%, respectively, were significantly higher (P<0.05) than severely affected fish (29.30 ± 2.34%). The same trend was observed for serum protein (7.09 ± 0.11 and 6.35 ± 0.27 g/100 ml for normal and apparently normal fish, respectively, against 4.68 ± 0.42 g/100 ml for severely affected fish) and hemoglobin (9.80 ± 0.26 and 9.70 ± 0.26 g/100 ml against 4.67 ± 0.42 g/100 ml) concentrations. The granulocyte counts of normal and apparently normal fish, 26.2 and 60.3, respectively were significantly lower than severely affected fish (210.0). This general hemodilution could be attributed to loss of body fluids and depression of hematopoietic tissues in the spleen and kidney

Experimental transmission of epizootic ulcerative syndrome (EUS) in snakehead, Ophicephalus striatus

Two separate experiments on transmission of epizootic ulcerative syndrome (EUS) to naive snakehead (Ophicephalus striatus) by cohabitation with EUS-positive snakehead in EUS-enzootic environment and exposure to EUS-enzootic environment alone were conducted in Laguna, Philippines. Under unfed conditions, initial signs of EUS were observed after 9 d of cohabitation and progressed into advanced stages in 10 tol6 d, whereas in exposure to EUS-enzootic environment alone, initial signs were observed in 10 d and developed into advanced stages in 15 to 20 d post-exposure. When food was given, initial signs of the disease were observed after 14 d of cohabitation and progressed into advanced stages in 17 to 20 d, whereas in fish exposed to EUS-enzootic environment alone, onset of EUS was 44 d post-exposure developing into advanced stages in 50 to 55 d post-exposure. Transmission of the disease was 100% in all treatments