Age validation and growth of yolked larvae of Patagonotothen tessellata (Richardson, 1845) (Pisces : Nototheniidae) from the rocky littoral of the Beagle Channel, Argentina

Age and growth estimation of Patagonotothen tessellata lan;ae over the endo genous period was estimated by examining their otolith microstructure and t he associated increment deposition rate. Analyzed specimens were incubated from egg-masses collected in Lapataia Bay, Beagle Channel, Argentina. Valid ation was performed by monitoring reared larvae of known ages. Actual age a nd increment count were regressed suggesting a daily deposition of one ring in the otolith, which began at hatching time and continued until larvae re ached sixteen days old (time of massive mortality). Mean lengths at each ag e were estimated using Richards' growth function; their constant (m) attain ed a value close to zero indicating that the data fitted to the von Bertala nffy model. Absolute growth rate was 0.55 mm*d(-1) of total length at hatch ing, dropped near zero on the fifth day after hatching and afterwards, ther e was no growth. Yolk absorption I ate (expressed as a ratio between minor axis/major axis of the vitelline-sac) showed a similar variation as that ob served in absolute growth rate during the endogenous period. The total yolk absorption took five days in the unfed larvae group and seven days in the fed larvae group. The rapid absorption of the yolk and the observed growth pattern suggest that Paragonotothen tessellata larvae have a short endogeno us period, reaching the state of first food uptake five days after hatching .