Optimising Polyculture Systems for Stichopus horrens: Effects of Tilapia and Rabbitfish on Growth, Survival, and Benthic Dynamics

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Introduction: integrated multi-trophic aquaculture (IMTA) offers a sustainable alternative to monoculture by combining species with complementary trophic roles to improve nutrient recycling and environmental performance. Within this system, deposit-feeding sea cucumbers such as Stichopus horrens function as extractive organisms that convert organic wastes into biomass while contributing to sediment remediation. However, empirical evidence remains limited regarding how co-culturing S. horrens with tropical finfish influences growth, survival, and benthic conditions.Method: a controlled tank experiment was conducted at the Kawasan Konservasi Ilmiah (KKI) Gondol, Indonesia, using twelve fibre-reinforced plastic tanks arranged in a completely randomised design. Four configurations were tested: S. horrens + tilapia (Oreochromis niloticus), S. horrens + rabbitfish (Siganus sp.), S. horrens monoculture, and a three-species assemblage. Each treatment consisted of three replicates with 15 sea cucumbers per tank. Growth performance, survival, faecal deposition, benthic community structure, and crustacean attachment were monitored throughout the culture period.Results: survival of S. horrens remained high across treatments (≈90–98 %, interpreted as 90–98 %), indicating strong tolerance to polyculture conditions. Monoculture produced the highest final weight (84,7 ± 34,8 g), followed by rabbitfish (75,3 ± 26,3 g), tilapia (61,3 ± 18,3 g), and the three-species system (54,9 ± 14,6 g). Rabbitfish grazing suppressed algal proliferation and benthic fouling, whereas tilapia-induced sediment disturbance reduced feeding stability. Crustacean attachment was lowest in treatments containing fish, suggesting secondary biofouling control.Conclusions: S. horrens can be effectively integrated into finfish polyculture, with ecological interactions strongly mediated by fish identity. Further research quantifying nutrient fluxes, stable-isotope assimilation, and benthic oxygen dynamics is recommended to refine stocking strategies and support system scalability.

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