Species composition of seaweed biofoulers in fish cage aquaculture in Bongao Channel, Tawi-Tawi, Philippines

Abstract

The excessive growth of seaweeds (macroalgal biofouling) on submerged cage structures is a severe operational constraint for fish cage aquaculture in tropical environments. This study investigated the species composition of macroalgal biofouling growing on the submerged structures of the fish cage aquaculture in Bongao Channel, Tawi-Tawi, Philippines, via a qualitative survey (e.g., snorkeling around the cage systems). The primary objective was to provide a taxonomic inventory of the colonizing seaweed species to understand the biological makeup of the fouling community. Through morphological examination of the collected samples, a total of 26 species belonging to 16 distinct genera were identified, representing the three major algal divisions: Chlorophyta (green algae) exhibited the highest generic richness, including <i>Boergesenia</i>, <i>Caulerpa</i>, <i>Chaetomorpha</i>, <i>Cladophora</i>, <i>Halimeda</i>, <i>Boodlea</i>, and <i>Ulva</i>. Rhodophyta (red algae) were represented by <i>Acanthophora</i>, <i>Actinotrichia</i>, <i>Chondrophycus</i>, <i>Yonagunia</i>, <i>Gracilaria</i>, <i>Hypnea</i>, and <i>Endosiphonia</i>, while Ochrophyta (brown algae) included <i>Padina</i> and <i>Sargassum</i>. The presence of various taxa, particularly filamentous <i>Chaetomorpha</i> and stoloniferous <i>Caulerpa</i>, identifies these groups as the key structural components of the biofouling community on the cage nets. Additionally, the inventory recorded the occurrence of economically valuable red algae (e.g., <i>Gracilaria</i> and <i>Hypnea</i>) and ecologically significant brown algae (e.g., <i>Sargassum</i>) within the assemblage. These findings establish a critical taxonomic baseline, providing the essential species-level data required to develop targeted mitigation strategies and sustainable management practices for the floating cage aquaculture in Tawi-Tawi.