Bacterial communities in sediments underneath milkfish cages and adjacent off‐cage areas in Bolinao, Lingayen Gulf, West Philippine Sea were characterized using PCR‐denaturing gradient gel electrophoresis to assess influence of the fish farming to the sediments. The sediments in the fish cage (FC) area showed anoxic conditions [redox potential of −165 to −213 mV and acid‐volatile sulphide‐sulphur (AVS‐S) of 0.55–1.88 mg g−1 (dry weight)] compared to the relatively oxic off‐cage area [redox potential of 72–81 mV and AVS‐S of 0.09–0.14 mg g−1 (dry weight)]. The composition of the microbial populations revealed influence of the fish feed sedimentation with higher dominance of putative sulphate‐reducing bacteria (SRB) in the FC area. Compositions of the bacterial taxa showed dominance of the Bacteroidetes group and Deltaproteobacteria. The results suggest that the fish feeds created a new suitable environment, in which reductive microorganisms such as SRB, ferric‐ion‐reducing bacteria and nitrate‐reducing bacteria can thrive. Organic load from the feed and quantity of its leftover constituents may be the key factors that influence the structure of the bacterial community in the sediments of the milkfish farms.

Philippines, composed of: seven-year (Tondol, Anda), nine-year (Pangapisan, Alaminos), 11-yr (Imbo, Anda), 12-yr (pilar, Bolinao, and 19-yr stands (Bangrin, Bani) were investigated. A modified local triangular trap net was deployed ~1 m from the edge of the plantation of each site at low tide for three days (before, during, and after spring tide) in December 2008 and February 2009. Fish samples were collected the following day, measured, then weighed in the laboratory. Fish species were categorized based on trophic level and habitat preferences. A total of 593 individuals belonging to 50 species from 22 families were recorded. There were no apparent trends in terms of fish abundance, fish biomass, and trophic categories with age of mangrove stands. In terms of habitat preference, mangrove-associated species dominated the mature plantation (> 12 yr) while reef-associated species were mostly found in younger stands (<12 yr). The fish assemblages have 43% similarity between seven-year and nine-year plantation and 35% similarity between 11-year and 12-year plantation. In contrast, the 19-yr old plantation was clearly separated from the younger plantations, indicating a possible shift of fish assemblage with age of mangrove stands.

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