Prolonged feed deprivation does not permanently compromise digestive function in migrating European glass eels Anguilla anguilla.

The effects of prolonged feed deprivation (40 days at 18° C) and re-feeding (30 days) on body mass, growth and the activity of selected pancreatic and intestinal enzymes were evaluated in migrating European glass eels Anguilla anguilla by comparison with a control group fed to satiation with hake Merluccius merluccius roe for the duration of the experiment. Feed deprivation resulted in mass loss and a reduction in digestive function, as revealed by a decrease in the total and specific activities of pancreatic (trypsin and α-amylase) and intestinal brush border (alkaline phosphatase and leucine aminopeptidase) enzymes. The total activity of intestinal brush border enzymes diminished after 5 days of feed deprivation, whereas that of pancreatic enzymes did not decrease until 10 days, indicating that the intestine is more sensitive to feed deprivation than the pancreas. Re-feeding A. anguilla that were starved for 40 days resulted in compensatory growth, with specific growth rates that were 2·6 times higher than the control group. This compensatory growth was associated with the recovery of trypsin and intestinal brush border enzyme activities, which were restored to control levels within 5 days of re-feeding. The ability to maintain pancreatic enzyme activity during 40 days of feed deprivation, and rapidly recover capacity for protein digestion upon re-feeding, would enable A. anguilla at this glass eel stage to withstand periods without food but rapidly provide amino acids for protein synthesis and growth when suitable food was available.