Sheltering behavior of the abalone, Haliotis tuberculata L., in artificial and natural seawater: The role of calcium

Abstract

There is an increased interest worldwide in developing land-based closed systems to cultivate the abalone, Haliotis tuberculata L. Here, we analyzed whether artificial conditions, and particularly the use of artificial seawater, might affect sheltering, a critical behavior of this species. The study was composed of two experiments. In the first, we compared sheltering between two groups of 100 individuals each reared in either natural or artificial seawater. For 15 days, a score was assigned every day to the position occupied by each individual, i.e. “0” when it was out of the hide, “1” when it was on the bottom of the maintenance tank underneath the hide, and “2” when it occupied the inner spot of the hide. Our results show that artificial seawater significantly affects sheltering: only the individuals reared in natural seawater were able to reach the hide and maintain a position in it. Chemical analyses revealed that artificial seawater differed from natural seawater for a relatively low concentration of Ca 2+. In the second experiment we compared H. tuberculata's sheltering behavior in three media, natural, artificial, and calcium-enriched artificial seawater. Sheltering was restored in enriched artificial seawater, which supports the hypothesis that calcium has an effect on this species' behavior. However, calcium concentration both in the artificial and “natural” water showed a progressive decrease with time likely due to the absorption by abalones, which suggests that in closed systems calcium supply is constantly required, even when the used medium is natural seawater.