Mortalidade mensal em uma população de Donax hanleyanus Philippi, 1847 (Mollusca, Bivalvia, Donacidae)

Maria Gil, GuaciraWillibaldo Thomé, José

The rate of instantaneous mortality, monthly mortality, and monthly survival were calculated to a population of Donax hanleyanus on a beach of Rio Grande do Sul, Brazil, by monitoring two age groups during 12 months. Distribution of monthly frequencies for 28 length classes was determined. A graph of the modal values permitted us the identification of two age groups in September, 1998, which were utilized in this study. The rate of instantaneous mortality (Z) was 0.715 (=71.5%); the rate of monthly survival (Sm) 0.489 (=48.9%) and monthly mortality (M) was 0.511 (=51.1%), to the two age groups, during the period between September, 1998 and June, 1999.