Vibrio are known opportunistic pathogens of pond-cultured fish and shrimp. This study determined the presumptive Vibrio count (PVC) and percentage composition of “beneficial” sucrose-fermenting vibrios (SFVs) and “pathogenic” non-SFVs in the water, sediment, gills and intestines of healthy tilapia Oreochromis niloticus collected every 2 weeks from Days 30 to 120 post-stocking in brackish water earthen ponds. PVCs in water and sediment ranged from 10²–10⁴ CFU/ml/CFU/g while in tilapias' gills and intestines, PVCs ranged from 10³–10⁶ CFU/g and 10²–10⁶ CFU/g, respectively, with SFVs dominating in water, sediment, gills (≥50%), and intestines (≥80%) of tilapia. Because use of tilapia-conditioned green water (TCGW) for shrimp's grow-out culture has been reported effective against acute hepatopancreatic necrosis disease outbreaks caused by V. parahaemolyticus, PVC, SFVs/non-SFVs (%), and V. parahaemolyticus count (VPC) in the recycled TCGW and Litopenaeus vannamei's hepatopancreas were also examined from stocking until 105 days of culture (DOC) in earthen ponds. PVCs ranging from 10²–10³ CFU/ml and 10³–10⁴ CFU/g were noted in water and shrimp's hepatopancreas, respectively. While non-SFVs population in water varied, a downward trend typified by an abrupt 50% reduction was noted in hepatopancreas at DOC 42, and remained or further dropped until DOC 105. VPCs in water likewise varied (undetectable–10² CFU/ml) while in hepatopancreas, counts dropped to undetectable level from DOC 70 onwards. Current data illustrate that remarkable shift of SFVs' dominance in the water and concomitantly in shrimp's hepatopancreas, plays a pivotal role in regulating non-SFVs proliferation in shrimp's hepatopancreas via competitive exclusion.

The characteristics of the seafloor environment of the harvesting grounds of the kelp, Saccharina longissima, were evaluated by spatial analysis using a geographic information system (GIS) in the Pacific coastal area of eastern Hokkaido. The kelp harvesting grounds were formed in water depths ranging from 1.2 m to 9.6 m, slopes ranging from 0° to 16.3°, bottom substrate (coarseness score) ranging from 1.82 to 3.00, bottom current velocities ranging from 0.7 cm/s to 116.4 cm/s, and a maximum slope of 37.6°. These values include the viable environmental conditions for the kelp. The kelp growth parameters estimated from kelp measurement data before the harvesting season were positively related to the bottom current velocity. This suggests that the bottom current velocity has a significant effect on kelp growth. The 58 harvesting grounds were classified into two categories based on their growth: those with high kelp growth and those with low kelp growth. Based on a decision tree model, the differences between the two harvesting ground categories were explained by the bottom current velocity, maximum slope, and bottom substrate. In addition, their specific environmental conditions were also quantified. The quantified environmental conditions were also used to create a potential map for the kelp growth in the harvesting grounds. This study provides an understanding of the environmental characteristics of the kelp harvesting grounds, as well as a procedure for mapping the kelp growth potential, thus contributing to the sustainable use of the kelp resources through kelp harvesting ground management and maintenance.

Despite the progress in the production of artificial diets for marine larvae, feeding during the early life stages of most aquaculture species still relies on live feeds such as rotifers. Advanced rotifer culture techniques are also available, however, in the Philippines, majority use batch cultures with fresh microalgae. These microalgae are prone to collapse resulting to inadequate supply of food for the rotifers that are fed to the larvae. Mangrove crab is one of the economically important aquaculture species in the country where mass seed production requires sufficient and steady supply of rotifers. Thus, here we examined the possibility of substituting fresh culture of green microalgae Tetraselmis tetrathele (FA) with flocculated T. tetrathele paste (FP) and commercially available Tetraselmis sp. (CP) as feed for rotifers (Brachionus rotundiformis) in the seed production of mangrove crab. Rearing of larvae was done until crab instar 1 (DOC 24) where growth and survival were taken to evaluate the viability of rotifers-fed microalgal paste. It was observed that the growth index (FA–6.93 ± 0.07; FP–6.91 ± 0.07; CP–6.96 ± 0.05) was similar for all treatments (P > 0.05) at termination. Comparable survival rates were noted for FA and FP at 1.08 ± 0.59% and 3.21 ± 2.09%, respectively (P > 0.05) while a significantly higher survival (P < 0.05) was recorded for CP at 7.73 ± 1.90%. These findings suggest that the algal paste tested are potential alternatives to fresh microalgae and this technique could benefit hatchery operators who lack the capital for setting up the facility and technical skills to maintain microalgae production.