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Volume 46 - Number 1 - 2011

Artícle


  

Density, abundance and population structure of the milk conch Strombus costatus of the Mexican Caribbean

Virginia Balán-Dzul1 y Alberto de Jesús-Navarrete2

1Instituto Tecnológico de Chetumal, Licenciatura en Biología, Av. Insurgentes 330, 77013 Chetumal, Quintana Roo, México
2Departamento de Manejo y Aprovechamiento de Recursos Acuáticos, El Colegio de la Frontera Sur, Unidad Chetumal, Av. Centenario Km 5.5, Apartado Postal 424, 77014 Chetumal, Quintana Roo, México

 

E-mail: anavarre@ecosur.mx

 

The milk conch Strombus costatus has rarely been studied at population and fisheries level in the Caribbean and Gulf of Mexico. To determine density and population structure of S. costatus at Banco Chinchorro, samplings was conducted using the method of distance during two seasons: summer (October 2008 and July 2009) and winter (November 2008 and February 2009), in order to evaluate the degree of aggregation we use the ratio variance/mean. With the size frequencies, growth parameters were obtained using FISAT II. 157 conchs were recorded, which showed an aggregate distribution. The highest density occurred in the winter season; 172 ind há-1 in the southern zone in November 2008, whereas in the central zone density was 77 ind há-1 in February 2009 and finally 51 ind há-1 in the northern zone in February 2009. The size structure varied between 80-165 mm siphonal length. The highest relative frequency value (FR) was detected in the south ranging between 111-115 mm LS. The infinite maximum length was L = 193.5, and a growth constant K = 0.38 with t0 = -0.51 was calculated. The rate of natural mortality was M = 1.062. The reported densities are higher than those reported in other Caribbean areas; however, the population of S. costatus could not support commercial exploitation at Banco Chinchorro. Densities of S. costatus have not changed over time, so milk conch is not displacing queen conch, which is subject to fisheries

 

Key words: Distance sampling, growth, Strombidae, natural mortality, population changes

 

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