Comparative study of the chemical composition, fatty acid profile, and nutritional quality of Lophiosilurus alexandri (Siluriformes: Pseudopimelodidae), a Brazilian carnivorous freshwater fish, grown in lotic, lentic, and aquaculture environments

ABSTRACT Lophiosilurus alexandri is a carnivorous freshwater fish endemic of São Francisco basin and an endangered species. In this study, we analysed the chemical composition (moisture, protein, ash and lipid), fatty acid profile, and nutritional quality (atherogenic index, thrombogenecity index, ratio between hypocholesterolemic and hypercholesterolemic fatty acids and ω6/ω3 = ratio) of L. alexandri in lotic (river), lentic (hydroelectric dams) environments, under natural fed, and in laboratory controlled conditions fed with commercial diets. Cultured and lentic fish had significantly higher lipid levels (1.5 and 1.9- fold, respectively) than lotic fish. Lentic L. alexandri had significantly higher eicosapentaenoic acid (EPA) levels (4×) than cultured or lotic L. alexandri. Docosahexaenoic acid (DHA) levels were the highest in lentic fish, followed by lotic fish. Lentic fish had greater proportion of fatty acid ω6/ω3 than lotic or cultured fish. The results of this study showed that L. alexandri is a lean fish (1-2% of total lipids) and that the environment has a great influence on the fatty acid profile. These results may be a reference for further studies, primarily as a source of information for conservation L. alexandri through restocking and the development of commercial projects of aquaculture.摘要 亚历山大钝头鮠（Lophiosilurus alexandri）是一种肉食性淡水鱼类，为圣弗朗西斯科河流域特有濒危物种。本研究针对不同生境与摄食模式下的该物种展开分析，检测了其化学成分（水分、蛋白质、灰分与脂质）、脂肪酸组成及营养品质指标（致动脉粥样硬化指数、血栓形成指数、低胆固醇脂肪酸与高胆固醇脂肪酸比值以及ω6/ω3比值）。受试个体分别取自流水生境（河流）、静水生境（水电站大坝库区），涵盖自然摄食状态，以及实验室可控条件下投喂商品饲料的养殖个体。养殖个体与静水生境个体的脂质含量显著高于流水生境个体，分别为其1.5倍与1.9倍。静水生境的亚历山大钝头鮠的二十碳五烯酸（eicosapentaenoic acid, EPA）含量显著高于养殖个体与流水生境个体，为其4倍。二十二碳六烯酸（docosahexaenoic acid, DHA）含量在静水生境个体中最高，其次为流水生境个体。静水生境个体的ω6/ω3脂肪酸比值高于流水生境与养殖个体。本研究结果表明，亚历山大钝头鮠属于低脂鱼类（总脂质含量为1%~2%），且生境对其脂肪酸组成具有显著影响。上述研究结果可为后续相关研究提供参考，尤其可为通过增殖放流开展亚历山大钝头鮠的物种保护，以及推进其水产养殖商业化项目提供数据依据。