Foraging behavior of Holothuria scabra juveniles on the sediment enriched with feces of Tripneustes gratilla fed with Sargassum spp.
摘要
Understanding the behavior and feeding selectivity of sandfish (Holothuria scabra) is crucial for assessing the viability of co-culture systems with sea urchins (Tripneustes gratilla). This laboratory study investigated the foraging behavior and growth of sandfish juveniles in sediment areas enriched with feces from caged Sargassum-fed sea urchins. Over a 14-day observation period, four 24-h monitoring periods were conducted to track sandfish distribution relative to the enriched areas, and growth performance was evaluated. By day 14, there was a higher incidence of sandfish under and around the perimeter of the caged sea urchin area during active hours (6 PM to 3 AM), though this pattern was not significantly different compared to other treatments. The significantly higher final weight and absolute growth rate (AGR) of sandfish in the sea urchin feces treatment (CG SU) (10.22 ± 0.11 g; 0.172 ± 0.17 g day−1), compared to cage-only (CG) and control (CTRL) treatments, which both exhibited negative growth rates (− 0.016 ± 0.09 and − 0.036 ± 0.12 g day−1, respectively), suggest that the juveniles were attracted to and foraged more on the feces-enriched sediment. Sediment analysis also revealed that chlorophyll-a and phaeophytin were higher near the cage in CG SU, though differences among treatments were not statistically significant. The highest chlorophyll-a concentration was found in the CG SU treatment near the sea urchin cage (A–F) (1.50 µg g−1) and had a positive correlation with AGR of sandfish. These results demonstrate that sandfish juveniles actively select and consume sea urchin feces-enriched sediment, confirming both the nutritional value of the feces and the potential for integrating sea urchin cage culture into sandfish grow-out systems.