Bioenergetics and nitrogen balance of the European eel ( Anguilla anguilla ) fed at high and low ration levels

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Owen, S F, Houlihan, D F, Rennie, M J, van Weerd, J H
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1998
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Anguilla anguilla; European eel
• Online Access: http://dx.doi.org/10.1139/f98-119; http://www.nrcresearchpress.com/doi/pdf/10.1139/f98-119

European eel (Anguilla anguilla) were fed either high or low ration levels (1.33 and 0.48% body weight·day 1 ). Eight periods of continuous 24-h respirometry in flow-through conditions were conducted over 70 days to simultaneously examine nitrogen and energy budgets without resorting to the calculation of parameters by difference. Food and oxygen consumption; ammonia, urea, and nitrate-nitrite excretion; and growth production were measured. Nitrogen budgets successfully accounted for 89.6-101.2% of the consumed nitrogen. Energy budgets accounted for 53.4-92.3% of the consumed energy. From the ammonia quotients (AQ), 54.4-57.7% of the available protein was oxidized at high ration, and 59.7-133.5%, at low ration level. To satisfy maintenance requirements, 0.28 mg N·g -1 ·day -1 was required. At 25°C eels were calculated to have a rate of standard metabolism of 83.3 J·g 1 ·day -1 , which is comparable with the range published for other species at this temperature. These data suggest that eels do not have a particularly low metabolic rate, as is commonly assumed in the eel rearing industry, and that the relatively inactive lifestyle associated with the eel masks a metabolic rate in common with other, more active, fish.