A feeding trial was conducted with juvenile red drum to determine their quantitative dietary requirement for arginine. Experimental diets with 35 g crude protein/100 g from red drum muscle and crystalline amino acids were used. Based on least-squares regression of feed efficiency and protein estimated requirement data, the minimum requirement of red drum for arginine was estimated at 1.44 ± 0.15 and 1.48 ± 0.12 g/100 g diet (4.11 and 4.23 g/100 g dietary protein), respectively. The arginine requirements estimated from weight gain data were 1.75 (± 0.18) g/100 g diet or 5.0 g/100 g dietary protein. These values are similar to those reported for other carnivorous fish species (Daniel et al. 2000).
Protein requirements of euryhaline fish such as the rainbow trout (Salmo gairdneri) and the coho salmon (Oncorhynchus kisutch) reared in 20‰ is about the same as the requirements for juveniles in freshwater (Krogdahl et al. 2003). No data are available for the protein requirements of these species in full strength sea water (35‰). Salmon, trout and catfish can use more protein than required for maximum growth because of efficiency in eliminating nitrogenous wastes in the form of soluble ammonia compounds through the gill tissue.