Abstract

The shell morphology of old, "stunted" ,or "piedra@" adults (in Venezuelan) of Strombus gigas and their vertical distribution have lead researchers to suggest that these individuals belong to populations or species different from those inhabiting shallow waters. On the other hand, alternative hypotheses point to differential migration rates and fishing effort as the cause of their distribution. Encouraged by this controversy, in this paper we study the vertical distribution of different growth stages of Stromhus gigas in Cayo Dos Mosquises Sur. In this locality, fisheries of Strombus gigas have been under control by personnel from the Marine Biology Station at Dos Mosquises. Consequently, the vertical distribution of this species is expected to be similar to that from a non-exploited, natural population. We used a principal component analysis to study to variables, measured in situ from each collected individuals (n = 553). Before this analysis was carried out, each individual was identified as juvenile. pre-adult, adult or old adult, according to the morphology of its shell as a whole. Depth intervals were grouped in two categories: shallow waters (less than 4 m) and deep waters (- 28 m). Results demonstrate that some growth stages overlap in shell morphology, suggesting that these variables not always discriminate among growth stages. Adults and old adults are found inhabiting shallow and deep waters, whereas juveniles and pre-adults are mostly found in shallow waters. These results suggest that the deep distribution of old adults reported in the literature may be the consequence of the inexorable exploitation of Strombus gigas inhabiting shallow waters.

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