Age validation and growth of Micropogonias furnieri (Pisces - Sciaenidae) in a temporally open coastal lagoon (South-western Atlantic - Rocha - Uruguay) based on otolith analysis

摘要

In this work 228 individuals of the whitemouth croaker Micropogonias furnieri collected in the Rocha coastal lagoon (Uruguay) from October 1997 to September 1998 were analysed. The species formed annuli in the otolith (sagitta) associated with the opaque zone (narrow opaque annulus), mainly in early winter when water temperature decreased, and reached the lowest values in July-August. The period of greatest growth occurred from December to June, partially overlapping with the spawning period (December-March) and in coincidence with the increase in marginal increment. Growth parameters determined for all individuals were K = 0.19, L-infinity = 30.2 and t(0) = -2.12. Annual growth increments showed that individuals grew rapidly and attained over 50% of their maximum observed size in the second year of life. In the third year, individuals attained sizes of first maturity at 11-12 cm less than estimates for the Rio de la Plata spawning area and coastal areas of Brazil. The increment in length-at-age in the Rocha coastal lagoon was smaller than in individuals inhabiting the continental shelf (up to 50 m depth).