Larval growth of hake (Merluccius hubbsi) in the Patagonian shelf: Analysis of two reproductive seasons

Abstract

The Argentine hake (Merluccius hubbsi) represents the most abundant fish resource in the Southwest Atlantic Ocean. Larval age, daily growth, and temporal distribution of birthdates of individuals collected throughout two reproductive seasons (2004–2005 and 2009) were studied by analyzing daily growth increments in their sagittae otoliths. Samples were obtained in the Northern Patagonian shelf, which constitutes the main spawning area reported for this species. A total of 365 hake larvae sampled with different types of gears was used in this study. Back-calculated hatching periods extended from mid November to the end of March and several larval cohorts were identified. Length-at-age relationships were best described by exponential models: TL=2.227 exp(0.032t) and TL=2.581 exp(0.035t) (for 2004–2005 and 2009, respectively). Growth rates obtained by deriving the models ranged from 0.07 to 0.48mm day−1 in 2004–2005, and from 0.09 to 0.74mmday−1 in 2009. Differences in larval growth were detected between both periods and within them; differential growth would not be attributed to thermal effect since temperature values were quite similar along both seasons. Prey availability could explain the growth variation detected within the 2009 season.