Bioaccumulation and Depuration of Emamectin Benzoate and Oxytetracycline in the European Black Sea Cucumber (Holothuria forskali): Implications for Aquaculture Integration

Sea cucumber ranching has been proposed as a sustainable, low-trophic source of seafood while remediating organic aquaculture waste. This exploratory study investigates the bioaccumulation and depuration of two finfish veterinary therapeutants, emamectin benzoate (EB) and oxytetracycline (OTC), in the European black sea cucumber (Holothuria forskali) within controlled conditions. Sea cucumbers (n = 80) were fed medicated aquafeed for 7 days, followed by tissue sampling at intervals up to 33 days. Mean initial tissue concentrations were 12.18 ± 0.99 ng/g for EB and 3.45 ± 2.90 µg/g for OTC. The elimination half-lives (t_1/2) were 10.7 days for EB and 23.1 days for OTC. Notably, 78% of sea cucumbers eviscerated their internal organs after exposure, and seven mortalities occurred. The sampled control animals (n = 20) were intact, indicating potential physiological stress from ingesting therapeutants. This exploratory study provides critical initial data on therapeutant impacts after ingestion by H. forskali, highlighting the need for further field validation to establish appropriate withdrawal periods for sea cucumber ranching within aquaculture systems using veterinary therapeutants.