Growth and production of an intertidal population of the chiton Plaxiphora aurata (Spalowski, 1795)

LÓPEZ GAPPA, J.; TABLADO, A.

VELIGER

California Malacozoological Society, Inc.

Año: 1997 vol. 40 p. 263 - 270

0042-3211

A population of Plaxiphora aurata was studied by non-destructive sampling from March 1994 to March 1995 at Quequ¨¦n (Argentina). Chitons occurred in hollows on shaded vertical walls, but were absent on horizontal substrata. Density fluctuated between 7.3 and 11.8 ind. m-2 (mean 9.5 ind. m-2). Recruitment occurred during early summer. Recruits were patchily distributed on the substratum during the early phases of benthic life, occurring in areas where larger chitons were rare or absent. A Von Bertalanffy growth model was fitted by simultaneous analysis of size-frequency distributions. This method gave an estimation of K= 0.359 and L¡Þ= 53.0 mm. Growth rate decreased in winter during the second year of benthic life, but not during the first year. The longevity of this species was estimated at 6-7 y. A survey of museum collections showed that maximum size was significantly correlated with latitude, reaching 95 mm in Tierra del Fuego. Annual production amounted to 3.51 g.m-2. y-1 (dry weight). Cohorts recruited in 1994, 1993, and 1992, accounted for 58%, 28&, and 12% of this total, respectively. Cohorts recruited in 1991 or before accounted only 2% of the total production. Mean annual biomass amounted to 3.44 g.m-2. The production/biomass ratio was 1.02.