| Popis: |
The protein and energy assimilated from eight main dietary algae by the stichaeid fishes Cebidichthys violaceus (Girard) and Xiphister mucosus (Girard) were calculated using bimonthly data on the chemical compositions (carbohydrate, protein, lipid) of these algae and the stomach contents and assimilation efficiencies of the two fish species. The effects of food choice on diet quality were estimated by comparing the amounts of energy and protein determined to be assimilated from the actual (selective) diets with those that would be assimilated from hypothetical (nonselective) diets based on algal availability. Both fishes consumed carbohydrate-rich, protein-poor algae in the winter and protein-rich, carbohydrate-poor algae during the rest of the year. Thus, contrary to an expectation from optimal diet theory, energy intake was increased by selection only during winter, whereas protein intake was increased at the expense of energy intake at all other times. Growth rates of the two fishes predicted by a growth curve based on the relative amounts of protein and energy assimilated from their diets were at or just above maintenance levels in winter and higher during other times of the year. The additional species of algae and the small amounts of animal material in the diets of the two fishes appeared not to alter substantially the predicted annual growth pattern. Although Cebidichthys violaceus and Xiphister mucosus seem to be able to grow during most times of the year on a completely algal diet, their rates of energy consumption, which in turn regulate protein intake, are unknown and must be examined before more definite conclusions can be drawn about the growth of these fishes. |
