Size at maturity of the Cortes geoduck Panopea globosa in Central Gulf of California

Abstract

This paper describes the size at maturity of the Cortés geoduck Panopea globosa in the central Gulf of California. The objective of this study was to determine the size at which 50% of the population is mature. The justification is that this value is still unknown  not only of this particular species, but in general, for other species of the genus such knowledge is scarce. Another justification for the study is that the minimum legal size in Mexican Cortes geoduck fishery, which is 130 mm in shell length (SL), was determined ignoring key biological aspects of the species in Mexico. Mexican geoducks were collected sub-tidal, 20 m to 25 m depth in Bahía Guaymas-Empalme, Sonora located in the Central Gulf of California in January 2014. A logistic model was used fit with the maximum likelihood criterion to get the size value at 50% maturity, which was 91.906 mm SL and 90.909 mm SL, female and male respectively. The analyses of the residual sum of squares showed both curves were not significantly different (F_0.284; p < 0.7547), demonstrating that the 130 mm legal size is larger than necessary if the size at maturity was the constraining requirement.