Dietary Sea Lettuce ( Ulva lactuca ) Enhances the Levels of Omega‐3 Long‐Chain Polyunsaturated Fatty Acids in the Muscle of Juvenile Nile Tilapia ( Oreochromis niloticus )

The effects of adding Ulva lactuca to the diets of Nile tilapia ( Oreochromis niloticus ) on growth performance, body composition, and fatty acid profiles were evaluated through a 12‐week feeding trial. Five isonitrogenous diets (30%; 300 g kg −1 crude protein) were prepared with increasing amounts of U. lactuca : (control, U 0 ), 5% ( U 5 ), 10% ( U 10 ), 15% ( U 15 ), and 20% ( U 20 ). Nile tilapia with an initial mean weight of 2.0 ± 0.01 g were randomly distributed into 50‐L flow‐through plastic tanks in triplicate and fed to apparent satiation twice daily. Fish fed the diet U 0 showed significantly higher weight gain (WG) and specific growth rate (SGR) compared with those receiving U. lactuca ‐based diets ( p < 0.05). Among the U. lactuca ‐based diets, the U 15 group achieved the highest growth with the final weight and SGR comparable to U 0 ( p > 0.05). Survival rates ranged between 90.7% and 96.7% and differed significantly among dietary groups ( p < 0.05). Inclusion of U. lactuca significantly influenced whole‐body proximate composition and fatty acid profiles ( p < 0.05). Levels of n‐3 long‐chain polyunsaturated fatty acids (LC‐PUFAs), particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), increased progressively with higher dietary U. lactuca inclusion ( p < 0.05), which may point to selective retention of LC‐PUFAs. Overall findings suggest that incorporating U. lactuca at 15% improves muscle n‐3 LC‐PUFA (EPA + DHA) content without substantially affecting growth, supporting its possible suitability in diets for juvenile Nile tilapia.