Evaluation of the red alga Gracilaria lemaneiformis and brown alga Sargassum horneri as ingredients in diets for white spotted snapper Lutjanus stellatus Akazaki juveniles

This study evaluated the red alga Gracilaria lemaneiformis and brown alga Sargassum horneri as ingredients to partially replace fishmeal in diets for white spotted snapper Lutjanus stellatus Akazaki (initial mass 12.0 +/- 0.1 g). Nine test diets containing 0 (control), 5, 10, 15, and 20% G. lemaneiformis or S. horneri were prepared; each diet was assigned to triplicate groups of fish in a total of 27 floating sea cages (each cage contained 30 fish). After a 60-day feeding trail, significantly lower final body weight, weight gain, and specific growth ratio were found in fish fed 20% G. lemaneiformis diet (P < 0.05), whereas the poorest fish growth performance was obtained with the 20% S. horneri diet. Lipid content in muscle of fish fed 20% G. lemaneiformis diet was significantly lower than that of other groups (P < 0.05); however, body protein was higher than that in other groups. The lowest lipid and moisture contents in muscle were recorded in fish fed 5 and 15% S. horneri diets, and protein content in whole body of fish fed 20% S. horneri diet was significantly lower than that of control and 5% diets (P < 0.05). Activities of pepsin in the stomach and lipase and amylase in the intestine were significantly suppressed in fish fed 20% G. lemaneiformis diet compared with that of control (P < 0.05). The lowest pepsin activity in stomach and lipase activity in intestine were observed in fish fed 20% S. horneri diet. Based on a quadratic regression model of weight gain, the results suggested that the maximum incorporation of G. lemaneiformis and S. horneri in diets should be 16.44 and 15%, respectively, for juvenile white spotted snapper.