Growth, mortality, and reproduction of Tagelus plebeius (Bivalvia: Solecurtidae) in Southeast Brazil

Tagelus plebeius (Lightfoot, 1786) is a stout razor clam that is economically exploited in several countries, including several local fisheries along the Bra- zilian coast. Despite its wide distribution and economic importance, there are few studies that have examined the population biology of this species. This study aimed to improve the current knowledge about the biology of T. plebeius by investigating its growth and mortality on a subtropical sandy beach in Southeast Brazil over a 1-year period. In addition, the reproduction of T. plebeius was analyzed through qualitative and quantitative histological analyses during the last 7 months of the study. The parameters of the von Bertalanffy growth function were estimated to be L? = 74.14 mm, K = 0.52 year -1 , C = 0.47, and WP = 0.94. The instantaneous mortality rate (Z) was 2.16 year -1 , and the life span was 2.58 years. We confirmed variations (H = 651.35; P \ 0.05) in the shell length over the months of the study, and the recruit- ment was higher—but still low—in summer. Four cohorts were observed in the distribution of shell length frequen- cies. The sex ratio of the population was 1:1 during the study period, and a synchronism in gonadal development and spawning was found between males and females. The high mortality (Z) and low recruitment rates can be inter- preted as reflecting that the population of T. plebeius is under a low restoration process and could be an indication that this species has an endangered status in the study area.