The impact of anthropogenic enrichment due to mariculture activity and substrate mesh size on periphyton characteristics and its consequent effects on the growth performance of post-settled (~5 mm) sandfish juveniles was evaluated in three sites (i.e. ENRiched , INTermediate , CONtrol ) along Guiguiwanen Channel in Bolinao
Northwestern Philippines using two different substrate mesh size (i.e. 400 µ m and 1 mm) in a 30-day field experiment. Growth and survival of sandfish juveniles were measured twice and periphyton chlorophyll a and ash-free dry weight (AFDW) were monitored every 5-days for 30 days. Sea slugs that recruited inside the mini-hapa nets were identified and counted during monitoring.
Mean length and absolute growth rates (AGR) was not significantly different between mesh size and across sites by D15; however, differences were significantly higher in enriched site by D30. Juveniles reared in the enriched site were significantly larger and grew faster compared to the juveniles reared in sites farther from the fish farm. Nevertheless, growth rate of juveniles across sites was relatively lower by D30 compared to D15. The decrease in average AGR by D30 could be attributed to reduced food availability as indicated by AFDW due to inter- and intraspecific competition. Periphyton chlorophyll a content was relatively higher during the second half of the experiment, however, total biomass as indicated by AFDW of periphyton generally decreased overtime. The decreased in food availability coincided with the increased in the number of sea slugs that recruited inside the mini-hapas
by D30. Survival significantly differ across sites but not mesh size by D15. Survival was significantly higher in intermediate site by D15. Differences in survival was significantly higher in juveniles reared in 400 µ m size across all the sites by D30. Overall periphyton characteristics and biomass was better and higher near the enriched site. Additionally, sandfish juveniles were larger and exhibited higher growth rates, indicating the viability of culturing post-settled sandfish juveniles near mariculture areas.