Abstract

The metabolic cost as measured by respiration and ammonia excretion rates associated with a natural diet as compared to an artificially balanced diet was determined for the juveniles of the Queen conch Strombus gigas. Two batches of 50 juvenile conchs of the same size class, were maintained with running, unfiltered seawater at a temperature of 26±1.5°C and, fed to satisfaction twice a day during 30 days. The natural diet consisted on an environmentally–inoculated and –grown multi-specific algal conglomerate of species which are known to grow on wild nursery grounds. The balanced diet was prepared by grinding and mixing into a jelly, a previously tested extruded balanced food. Juveniles were maintained in 200 L aquariums with running unfiltered sea water at 26±1.5°C during 1 month. Respiration and excretion trials were all run at of 26±0.5°C, in a thermo-regulated water bath during measurements. Conchs withstood a 20 day starvation period without mortality. Preliminary observations showed a decline of oxygen consumption rates during starvation. An increase of ammonia excretion and, a decline in O:N ratios were also observed. The amount of energy reserves as observed by histo-chemistry of the digestive gland tissue increased in relation to the quality of food offered and decreased, substantially, following starvation. These results are of meaningful importance for the construction of an energy balance for the juvenile stages of Strombus gigas; and for a better understanding of the underlying physiological processes of nutrition and growth of the species under culture conditions

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