Population Structure of the Shrimp Alpheus estuariensis (Caridea: Alpheidae) in a Tropical Estuarine Tidal Mudflat

This study investigated recruitment, sex ratio, growth, longevity, density, and distribution pattern of a population of the snapping shrimp Alpheus estuariensis in a tropical estuarine tidal mudflat in northeastern Brazil. Individuals were captured monthly from September 2011 to October 2012 in Pontal Bay, Ilh,us, Bahia, Brazil. In total, 863 shrimps were collected: 311 males, 305 females (134 breeding and 171 non-breeding), and 247 juveniles. Individuals smaller than 5.9 mm (carapace length of the smallest breeding female) were considered juveniles. Both adults and juveniles occurred throughout the sampling period. Although there was no relationship between abundance and environmental factors (temperature, rainfall, and salinity), some months had more individuals than others. Recruitment was continuous. Total and monthly sex ratio did not differ from 1:1 (M:F). The sex ratio by size-frequency class (carapace length) was similar to Wenner's "Standard Pattern"; however, no deviation in favor of males was observed in the largest size classes. Compared with Gompertz and logistic functions, the von Bertalanffy Growth model gave the best fit to the data, describing growth with the equation: Length = 14.64*(1-e((-1.21*(age-0.03)))). The estimated life span of A. estuariensis was 1.07 years. Juveniles and adults were more abundant in small grain size sediments, which might facilitate excavation during shelter construction.