Age and growth of puyen, Galaxias maculatus, from Parque Nacional Tierra del Fuego, austral Patagonia (54ºS)

ROJO, J.H.; BOY, C.C.; FIGUEROA, D.E.

Albuquerque

Congreso; Joint Meeting of Ichthyologists and Herpetologists; 2013

Kansas State University

We present the first results on age-growth of a diadromous population of Galaxias maculatus at the southernmost limit of its distribution (Parque Nacional Tierra del Fuego, Patagonia, 54ºS). Individuals were captured monthly during spring-summer (October 2003 - February 2004), which is the growing and reproductive season. Age of 169 individuals was estimated trough growth layers on otholits. Then, the von Bertalanffy growth model was fit to age-length data through non-linear methods with R language (http://www.R-project.org/). Maximum age was established on 3 years. During the first two months of the reproductive season (October and November) two-year individuals represented 60% of the population, whereas during the last three months (December ? February) one-year individuals represented 90% of the population. At the beginning of the summer (December) it was observed the incorporation of juveniles (whitebait) returning from feeding at sea and this whitebait represents 90% of the one-year individuals. Study of length shows the growth of the one-year cohort, given that mode shifts from 60 to 65-70mm between December and February. Towards the end of the reproductive season, there were not observed three-years individuals, suggesting natural mortality and those older individuals will not survive to the next winter. Parameters from the von Bertalanffy model were for females: Linf=89.3562 ± 3.9656, k=2.5589 ± 2.2951, t0=-0.4837±0.4226; and for males: Linf=81.909 ± 4.161, k=1.698 ± 1.082, t0=0.138±0.462; suggesting that females reach a higher maximum length than males.