Living on the edge: population parameters of the wedge clam Donax hanleyanus in its southernmost limit of distribution range, Southwest Atlantic, Argentina

LOMOVASKY BETINA J.; RISOLI MARIA C.,; DEFEO OMAR,

CANADIAN JOURNAL OF ZOOLOGY

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Lugar: Otawa; Año: 2021 vol. 99 p. 713 - 720

0008-4301

The wedge clam Donax hanleyanus is a conspicuous member of the sandy beach macrofauna along hundreds of km in the northern coasts of Argentina. Age, growth, mortality and productivity of this species were assessed in its southernmost limit of distribution range (Mar del Plata, Buenos Aires Province, Argentina). The von Bertalanffy growth function parameters were SL∞ = 23.23 mm, K = 1.623 year-1, t0 = 0.082 years. The maximum individual production amounted 7.9 x 10-7 g shell-free wet mass (SFWM)·year-1 at a shell length of 14-16 mm. Individuals between 10- mm and 12-mm contributed the most to the population secondary production P of 0.01 g SFWM·m-2·year-1. The mean annual biomass B was of 0.002 g SFWM·m-2·year-1. Annual P/B ratio and mortality coefficient Z were 4.48 year-1 and 4.78 year-1, respectively. Low production and high mortality could be caused by a sharp decrease in the habitat quality, given by suboptimal temperatures at the southernmost edge of the species distribution. These results strongly limit its potential in a future scenario of commercial exploitation.