Volume 58

Density and Distribution of Strombus gigas Linnaeus, 1758 (Mollusca: Strombidae) Population Structure Associated to Different Habitats in Archipiélago Nuestra Señora del Rosario, Caribbean


Authors
Gómez-Campo, K., M. Rudeda, C. García-Valencia, F. Ballesteros, L.E. Mejía
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Date: November, 2005


Pages: 399-406


Event: Proceedings of the Fifty Eighth Annual Gulf and Caribbean Fisheries Institute


City: San Andres


Country: Colombia

Abstract

Density and distribution of S. gigas as well as its association to different kind of habitats was explored through a survey of 184 stations organized systematically in two seasons (rainy and dry). Each individual was counted and measured in a circular area of 1,256.6 m2 with SCUBA, whereas in situ observations about habitat characteristics were conducted simultaneously. Total densities were among the lowest reported in the Caribbean, 4 ind/ha ± 10.8 and 3.7 ind/ha ± 9.3 for both rainy and dry seasons. Adults (shell length > 22 cm) represented 89 and 64% of the population, concentrated in Bajo Tortugas and Isla Tesoro. Even though reproductive activity was observed during rainy season, densities were below critical levels that could guarantee reproductive success in the population, indicating potential occurrence of the “Allee Effect”. The extension and distribution of available habitat and the frequencies of observations in each habitat, allowed identify habitat association for S. gigas. Densities of adults were higher during rainy season on ‘rodolitos-sand’ habitat (RdA) (<25 ind/ha), followed by ‘sand-rubble’ (AC) and ‘mixed bottom’ (Fmx) habitats (< 5 ind/ha). Juveniles were associated to ‘seagrass’ habitat (Pp) and AC. During dry season adults were concentrated on RdA, AC and Fmx in similar proportions, while juveniles gathered again in Pp, followed by algal plain, AC, and Fmx. Reproductive behavior of conchs during rainy season was observed on RdA and AC habitats. Multiple regressions models explained 48 and 14% of the total variance in the abundance of adults during rainy and dry seasons, respectively; with depth, mean grain size and percentage of mixed coral as predictor variables. Management implications of the above findings suggest protection of Pp, AC and Fmx habitats, which gathered juveniles and spawning stock of the queen conch.

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