Age, growth and hatch-dates of Brevoortia aurea larvae.

BROWN D.; ACHA E. M.

Kiel, Alemania

Congreso; 32nd Annual Larval Fish Conference; 2008

Brazilian menhaden, Brevoortia aurea is the only species of the genus Brevoortia in the South American Atlantic waters being abundant in the Río de la Plata estuary. Little is known about aspects of its early life history, and this is the first attempt to study species larval growth. Age and growth parameters of B. aurea larvae were determined by analysing daily increments in sagittae otoliths. Two larval groups were collected on 13 January and 27 February 1999. A total of 175 specimens (20 – 60 mm standard length) were analysed. A linear model was fitted to the length-at-age data of larvae: L(t) = 0.39 t + 4.95, were slope (0.39) represented mean growth rate in mm day -1 . This growth rate was similar to the values observed in other species of Brevoortia genus from the Northern Hemisphere. Individual mean growth rates estimated for each group of larvae were 0.38 and 0.41 mm day -1 (January and February respectively). Difference was statistically significant between groups, and could be attributable to thermal influence during the different hatching seasons of those cohorts (spring and summer). Mean widths of the increments represented as a function of the age varied from 4.5 to 5.8 microns for January larvae, and from 5.2 to 6.3 microns for February ones. Differences of increment widths were also significant between both groups of larvae reinforcing the hypothesis of seasonal variation