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

RISOLI, M.C.; DEFEO, O.; LOMOVASKY, B.J.

CANADIAN JOURNAL OF ZOOLOGY

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Año: 2021 vol. 99 p. 713 - 720

0008-4301

The wedge clam Donaxhanleyanus Philippi, 1845 is a conspicuous member of the sandy beachmacrofauna along hundreds of kilometres in the northern coasts of Argentina.Age, growth, mortality, and productivity of this species were assessed in thesouthernmost limit of its distribution range (Mar del Plata, Buenos Airesprovince, Argentina). The parameters of the von Bertalanffy growth functionwere SL∞ = 23.23 mm, K = 1.62 year-1, and t0= 0.08 years. The maximum individual production was 7.9 x 10-7 gshell-free wet mass (SFWM)·year-1 at a shell length of 14-16 mm.Individuals between 10 and 12 mm contributed the most to the secondaryproduction (P) of 0.01 g SFWM·m-2·year-1. The meanannual biomass (B) was 0.002 g SFWM·m-2·year-1.Annual P/B ratio and mortality coefficient (Z) were 4.48 year-1and 4.78 year-1, respectively. Low production and high mortalitycould be caused by a sharp decrease in habitat quality, given the suboptimaltemperatures at the southernmost edge of the species distribution. Theseresults strongly limit its potential for future commercial exploitation.