be 47 or 22 g digestible proteinrMJ digestible energy. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: American eel; Anguilla rostrata; Protein requirement; Elver; Optimum growth; Digestibility
1. Introduction
American eel culture is a relatively new industry in Atlantic Canada. Due to environmental constraints, particularly low winter water temperature in the Atlantic
provinces, a recirculation system must be used to rear wild elvers to market size. Feeds used for this system should be water-stable and highly digestible to minimize nitrogen,
phosphorous and solid output to the aquatic environment. Unfortunately, information on the nutrient requirements of American eel is limited and there are no published data on
nutrient bioavailability from locally available feed ingredients.
Dietary protein supply is one of the major factors that influence the productivity of fish and the production of nitrogenous waste material that is excreted in water. Like
other fish species, the reported protein requirement of Japanese eel and European eel is Ž
. relatively high compared to terrestrial animals
National Research Council, 1993 . Ž
Although the protein requirement of Japanese eel has been investigated Arai et al., .
1971, 1972; Nose and Arai, 1973 and is 44.5 of the diet, reported values for European Ž
eel range from 30 to 48 Spannhof and Kuhne, 1977; Degani et al., 1984, 1985; Arai .
et al., 1986 . Dietary requirement for protein is, in fact, a requirement for the essential amino acids contained in the dietary protein. The quantitative amino acid requirement
Ž .
values for Japanese eel Nose, 1979 are commonly used for feed formulation of both American eel and European eel.
Dietary energy concentration has a profound effect on how well protein is utilized. Ž
. Studies have indicated that American eels Otwell and Rickards, 1981 , Japanese eels
Ž .
Ž .
Takeuchi et al., 1980 and European eels Dave et al., 1974, 1976 efficiently utilize fat as an energy source.
The present study was designed to determine the quantitative dietary crude protein requirement for optimum growth of juvenile American eel using a practical fish-meal-
based diet and to measure the digestibility of nutrients from the experimental diets. This information is necessary for cost-effective feed formulations, to optimize growth and
protein retention and reduce the soluble and solid load of nitrogenous compounds in the water used for eel culture systems, particularly in recirculation systems.
2. Materials and methods
