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An experiment was conducted to investigate the effects of phosphorus (P), citric acid (CA) and formic acid (FA) supplementation on growth and loading of nitrogen (N) and phosphorus (P) in juvenile yellowtail fed fish meal (FM) and alternate plant protein (APP) diets. Six diets designated as F49 (490 g kg )1 FM-based), F49 + P (490 g kg )1 FM with 5 g kg )1 inorganic P), F31 + CA (310 g kg )1 FM containing 200 g kg )1 APP with 5 g kg )1 CA), F31 + FA (310 g kg )1 FM having 200 g kg )1 APP with 4 g kg )1 FA), F23 + CA (230 g kg )1 FM containing 300 g kg )1 APP with 5 g kg )1 CA) and F23 + FA (230 g kg )1 FM having 300 g kg )1 APP with 4 g kg )1 FA) were formulated. Yellowtails were fed one of the diets for 12 weeks under on-site conditions at water temperature 22.0-27.0°C. F49 + P gave the best growth, while F23 + CA the lowest. Specific growth rate and feed conversion ratio of F31 + CA were similar with control group. Addition of CA to APP diets significantly increased retention of P; hence, its excretion was lowered. The results of this study suggest that FM could be replaced up to 70% with the addition of 5 g kg )1 CA to a low P-containing plant protein sources diet without inorganic P supplementation in juvenile yellowtail diets, which in turn would enable a reduction in environmental pollution from aquafeeds.

A feeding experiment was conducted to investigate the e¡ect of organic acids and/or lipid supplementation on growth, utilization and environmental loading of nitrogen (N) and phosphorus (P) in juvenile yellowtail fed ¢shmeal (FM) and plant protein (PP) diets. Six diets as FM (FM-based), FM1P (FM with inorganic P), FM1L (FM with lipid), PP1CA (PP with citric acid), PP1L1CA (PP with lipid and citric acid) and PP1L1FA (PP with formic acid) were formulated.Yellowtails were fed each of the diets in duplicate groups; once a day,6 days a week to near satiation at water tem-perature19.0^25.0 1C for16 weeks. Fishmeal with inorganic P gave the best growth while PP1L1FA the lowest. However, growth increased in PP1CA and PP1L1CA. Addition of lipid signi¢cantly increased N and P retention resulting in signi¢cant reduction in N and P excretion. Citric acid and FA supplementation to PP diets also increased retention of P; hence, its excretion was lowered. Thus, CA, FA and lipid in juvenile yellowtail diets can help to partially replace FM with PP sources and reduce inorganic P use to minimize environmental loading from aquafeeds.

This study investigated the effects of dietary fatty acids and water salinity on fatty acid composition and expression of the fatty acid desaturase (fads)-like and elongase (elovl)-like genes of red sea bream Pagrus major. Sequence and phylogenetic analyses revealed that the fadslike and elovl-like genes isolated in this study encoded fads6 and elovl5, respectively. There was no significant difference in growth performance or proximate composition of fish fed diets formulated with 100% fish oil (FO) (FO diet) or with 67% of FO substituted with canola oil (VO diet). Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents were significantly higher in liver of fish reared at 15 and 20 ppt than those at 33 ppt. The liver fatty acid desaturase gene transcript was detected by reverse-transcription polymerase chain reaction (RT-PCR) in liver of fish fed the VO diet at 15 ppt, but not at either 20 or 33 ppt. The elovl5 gene was clearly expressed in liver for all treatments. These results suggest that red sea bream could synthesize EPA and DHA from their precursors in liver and that EPA and DHA biosynthesis potency was stimulated at lower salinity.

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