Healthy and Wholesome Aquaculture

pots while tilapias were stocked in a blue drum that serves as fish holding tank. Training on aquaponic systems would be organized soon.

Testing the efficacy of indigenous probiotics

The use of bacteriophages, vaccines, probiotics, prebiotics, and recently the application of poly-β-hydroxybutyrate (PHB) and quorum sensing disruption have been developed and tested as means of minimizing or limiting the use of antibiotics in aquaculture. The protective effect of Bacillus sp. JL47 containing

different levels of amorphous PHB was examined using the gnotobiotic Artemia. Isolate of Bacillus sp. was grown to accumulate different levels of amorphous PHB (29% and 55% PHB on cell dry weight) and fed to gnotobiotic Artemia nauplii during a Vibrio campbellii LMG 21363 challenge test.

Results showed that Artemia nauplii fed the Bacillus sp. JL47 containing 55% PHB attained a significantly higher survival than those Artemia fed the Bacillus sp. JL47 containing 29% PHB. Complete protection against the pathogenic V. campbellii was observed in Artemia fed the Bacillus sp. JL47 containing 55%

PHB. The data suggest that, the protective effects of Bacillus sp. JL47 is superior when it contains higher amount of amorphous PHB and that the amorphous PHB is suggested to be a main determinant in the protective effect of the Bacillus sp. JL47.

When P. monodon was challenged with V. parahaemolyticus 1213 strain, survival was highest (76.25%) in shrimps fed formulated diet supplemented with 1 g Bacillus sp. JL47 per kg, followed by shrimps fed the 0.5 g/kg (67.5%). Shrimps fed the formulated diet containing 2 g/kg attained survival of 36.25% while the lowest survival was observed in shrimps fed the control diet (without Bacillus sp. JL47 supplementation; 28.75%). The non-challenged shrimps (control) attained a survival of 92.5%. This suggests that the addition of amorphous PHB-accumulating Bacillus sp. JL47 can protect the shrimp against AHPND caused by V. parahaemolyticus 1213 strain. The suggested dose of supplementing Bacillus sp. JL47 in the feed is at 0.5-1.0 g bacterial weight per kg feed.

Penaeus indicus post-larvae produced from domesticated broodstock (left) and stocking of P. indicus PL 15 (right)

Transmission electron micrograph (TEM) of probiotic Bacillus sp. JL47 strain containing the intracellular amorphous

PHB

Rationalizing the need and application of diagnostics that ensure biosecurity within culture systems

The Province of Capiz in central Philippines is one of the major producers of oysters in the country. AQD determined the microbial quality of oysters (Crassostrea iredalei) grown in Capiz Province by investigating the major oyster production sites located along the coastal villages of Roxas City, Ivisan and Pan-ay for fecal coliform, Escherichia coli, Vibrio parahaemolyticus, and presence of V. cholerae and Salmonella in the rearing water and oysters’ meat, respectively. The results indicated that the monthly coliform count in the water samples collected from all sampling stations were generally high (≤ 540 MPN/100 ml) regardless of the sampling period (wet or dry season). Similarly, the monthly E. coli count in oysters’ meat and intervalvular fluid were typically high (330~24,000 MPN/100 g) particularly during the warm dry months of the year. V. parahaemolyticus count quantified in oysters’ meat samples examined was <3.0 MPN/g which is within the acceptable limit set by the Singapore Guideline (<100 MPN/g). Results for cadmium, chromium, lead, and mercury were below (nil) the limit of detection for all sampling sites. V. cholerae was not detected in any of the oyster samples examined.

Survival of shrimps after a V. parahaemolyticus 1213 (VP) challenge, where prior to the challenge, shrimps were fed with a shrimp diet supplemented with different levels of Bacillus sp. JL47 for 15 days

Stake method: traditional method of culturing oysters in Cabugao, Ivisan, Capiz (left); traditionally cultured oysters in Agojo River, Pan-ay, Capiz (right-above); one of the rafts used for the relaying

experiments in Cabugao Bay, Ivisan, Capiz (right-below)

All the oyster culture sites examined belong to Class C category of the EU Shellfish Area Harvesting Classification, indicating that oysters harvested from these areas are still safe for human consumption provided that they undergo proper relaying and depuration procedures or subjected to an approved method of cooking. Relaying oysters in an approved area in Cabugao Bay, Ivisan was attempted, and the results indicated significant drop in E. coli count in contaminated oysters from 24,000 MPN/100g to ≤ 20 MPN/ 100g after 2 weeks of relaying, suggesting the practicality of this technique in rendering raw oysters safe for human consumption.

Preventing and mitigating incidence of diseases in cultured mangrove crabs

The indicators responsible for disease occurrence or outbreak in cultured shrimps have been investigated considering that vibriosis and white spot syndrome virus (WSSV) have also persistently caused mortalities in mangrove crabs, i.e. vibriosis in the hatchery phase and WSSV in the grow-out phase. In shrimp culture, the mortality due to WSSV infection could be due to the viral load and environmental conditions such as low water temperature, while WSSV could be present in pond soil and water that serve as vehicle for infection.

To address these concerns, the threshold levels for WSSV in the water, soil, and system in mangrove crab culture that could result in infection and mortality or outbreak were examined in vitro and in vivo.