The effect of feeding frequency on utilization of algal nutrients by the marine herbivore, the luderick, Girella tricuspidata (Quoy and Gaimard)

Utilization of whole algae, lipid, protein and total nitrogen and total carbon by the luderick, Girella tricuspidata , fed ad libitum were found to be comparable with published results obtained for other species. Periods of food deprivation were found to cause reduced efficiency of utilization for all nutrients measured, with a 4–day deprivation period having a greater effect than a 24–h deprivation period.
Only animals fed ad libitum were able to obtain a greater amount of lipid from their food than was defaecated. Utilization of protein and non–protein nitrogen is similar in fish fed ad libitum , but a greater reliance upon the non–protein nitrogen content of the food for nutrition is apparent when the fish are subjected to periods of food deprivation. Nitrogen utilization, relative to other nutrients, by fish subjected to periods of food deprivation is greatest immediately after a feeding bout. Total carbon utilization relative to other nutrients increases with increasing time of deprivation following a feeding bout.
It is suggested that these changes in nutrient utilization with time after feeding are the result of rapid utilization of the nitrogen–rich cell contents, followed later by utilization of the algal cell wall.