Effects of Water Quality, Stocking Density, Water Exchange Frequency, and Food, on Growth and Survival of the Green Mussel, Perna viridis Larvae

Experiments were conducted to determine the optimum conditions for growth and survival of the green mussel, Perna viridis larvae. Effects of various temperatures and salinities, stocking densities, water exchange frequency, and natural food preference of the larvae from D-hinged to pediveliger stage were investigated. The green mussel broodstocks were collected from the natural source, and spawning occurred in captivity. All experiments were conducted in triplicate. The results demonstrated that larvae from D-hinged to pediveliger stage had better growth and survival when the temperature was between 29oC and 30oC, and salinity ranging from 30-33ppt. Stocking density from 10- 20 larvae/ml did not affect growth and survival of the larvae. Likewise, frequency of water replacement from daily to every 5 day interval did not influence the growth and survival until the pediveliger stage. During this stage, the larvae preferred a combination of Isochrysis galbana and Chaetoceros calcitrans as food in terms of better growth, and either Isochrysis galbana, Chaetoceros calcitrans, or their combination in terms of higher survival rate

Establishing mollusk colonization and assemblage patterns in planted mangrove stands of different ages in Lingayen Gulf, Philippines

We investigated the assemblage patterns and species composition of infaunal mollusks in different ages of planted mangroves (6-, 8-, 10-, 11- and 18-year old) in Lingayen Gulf, northwestern Philippines. The study aimed to determine if the mollusk assemblage was associated with the developing forest and if such patterns could provide evidence for restoration of habitat functionality. A total of 11 mollusk species were recorded. Only two species, Cerithidea cingulata (Gmelin, 1791) and Nerita polita (Linnaeus, 1758), consistently appeared in all stands where the former had increased biomass in maturing stands and the latter peaked in intermediate age stands. Vegetation structure and biomass, and sediment characteristics changed as plantations matured. Likewise, mollusk assemblages (based on species composition and biomass) significantly varied among different age stands. Such changes in assemblage patterns were correlated with vegetation and sediment characteristics. The groupings of mollusks species in the different stands can be categorized into: decreasing (species that have initially high biomass but disappeared in older stands); no detectable change (species that did not show any change in biomass); peaking (species that initially had low biomass, peaked at intermediate stands, and then diminished in mature stands; and, increasing (species that have increasing biomass with maturing stands). In summary, this study affirmed: (1) rehabilitated mangroves with increased forest structure and biomass can be effective in facilitating infaunal colonization; and (2) mollusk assemblage patterns changed as stands grow older