Population dynamics, growth, production, and reproduction of the purple clam Amiantis purpurata

Abstract

Amiantis purpurata is the dominant clam of shallow subtidal soft bottom communities in Buenos Aires province where it is a major prey item of economically important fish and gastropods as well as anemones. Despite its significant role in the benthic food web, there are few studies dealing with the population biology of this species. Growth, age, mortality, and production along with reproductive patterns and size at first maturity of A. purpurata were investigated at Mar del Plata (38 ºS) area and compared with a population at the southernmost point of distribution, the only other studied population (42 ºS). Early growth was empirically documented for the first time for this species by following a newly recruited cohort throughout the first two years of growth. This allowed for the size and age at first maturity to be accurately determined and provided early growth data for models, which are often difficult to obtain. Larger asymptotic size and quicker rates were reached at lower latitudes. Reproduction followed patterns similar to other temperate venerid bivalve populations with a more extended period of spawning observed at Mar del Plata. The studied population shows relatively high growth rates, achieves sexual maturity at approximately two years of age, and successfully recruits in this area, which was not observed in the other studied population for over 15 years. The environmental conditions in this area are likely more favorable than that of the southernmost population which shows low growth rates and no successful recruitment.