Resumo

FLORES-CAMPANA, Luis Miguel; GONZALEZ-MONTOYA, Marco Antonio; ORTIZ-ARELLANO, Mónica Anabel  e  ARZOLA-GONZALEZ, Juan Francisco. Population structure of Chiton articulatus from Pájaros and Venados islands of Mazatlán Bay, Sinaloa, Mexico. Rev. Mex. Biodiv. [online]. 2007, vol.78, suppl., pp.23-31. ISSN 2007-8706.

This work represents a contribution to the knowledge of the basic and fishery biology of Chiton articulatus, which is exploited by amateur fishermen along the coast of Mazatlán, Sinaloa. Collections were made every two months from February to December of 2000 at four different sites in the intertidal zone of Pájaros and Venados islands, during the lowest tide. Two sites were in the protected zone facing Mazatlán Bay and two in the exposed zones of both islands. All specimens were identified and measured in the laboratory where body size and weight were obtained with a caliper (±0.1 mm) and scale (± 0.001g) respectively. The total length (Lt) of the 1,236 specimens examined varied between 11.2 and 86.8 mm, height (Al) between 2.0 and 48.1 mm, width (An) from 7.1 mm to 48.1 mm and total weight (Pt) from 0.1 g to 53.8 g. Size distributions showed that most of the population was between Lt of 31 - 64 mm with a modal Lt of 41.1 mm and mean of 45.6±8.5 mm. The larger sizes were recorded on the exposed zone of Pájaros island and the smaller sizes were found in the protected zone of Venados island. This difference can be explained by wave exposure and differences in fishery pressure related to the ease of access to each zone. Biometric relationships between sizes were linear {An=0.5423(Lt)+2.7594, Al=0.2316(Lt)-0.4576 and Al=0.3807(An)-0.3832} and between size and weight were exponential {Pt=0.0001(Lt)^2.8404, Pt=0.0005(An)^2.8807 and Pt=0.0329(Al)^2.3236}; the values of slope (b) between size and weight relationships were close to 3, indicating isometric growth. The relationship between Pt and foot weight (Pp) was {Pt=4.8778(Pp)+1.0933}, which means that the portion of each specimen used was 17 % of Pt. Capture of C. articulatus is a subsistence activity for different groups for temporary relief in times of poor catches or to complement earnings from other activities. There are no regulations governing the harvesting and commercialization of this mollusk.

Palavras-chave : molluscs; Chiton articulatus; Eastern Tropical Pacific; islands; size distribution; fishery.

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