Seasonal variations in the growth of anchovy larvae (<i>Engraulis anchoita</i>) on the Argentine coastal shelf

Abstract

SUMMARY: Age and growth rates of the anchovy larvae (Engraulis anchoita) in Argentine waters were estimated by analysing daily growth increments in sagittal otoliths under light microscope. The samples were collected during 2000 on the Argentine coastal shelf using a Bongo net. A total of 251 larvae were analysed (size range 3.5 to 12.2 mm standard length). Length-at-age and standard length-otolith radius relationships were best described by linear models. We put forward the hypothesis of differential larval growth in anchovy in relation to seasonality. Mean growth rates at four days before capture were determined by back-calculation and analysed in relation to temperature. The growth rate values obtained from the linear growth models were 0.51 mm day -1 (spring), 0.41 mm day -1 (summer) and 0.42 mm day -1 (autumn). Significant variations were detected between spring and summer and between spring and autumn. These variations do not seem to be associated with a thermal influence.Keywords: anchovy, Engraulis anchoita, larval growth, otoliths, age. RESUMEN:Variaciones estacionales en el crecimiento de larvas de anchoíta (Engraulis anchoita) en la zona costera argentina. -Se determinó la edad y el crecimiento de larvas de anchoíta (Engraulis anchoita) mediante el conteo y medición de los incrementos diarios de los otolitos sagitta. Las larvas fueron capturadas en la Plataforma Costera Argentina durante el año 2000 por medio de una red Bongo. Se analizaron un total de 251 larvas entre 3.5 a 12.2 mm. Las relaciones talla-edad y talla -radio del otolito se representaron mediante modelos lineales para cada estación del año (primavera-veranootoño). La mayor tasa de crecimiento, calculada como la pendiente de los modelos talla -edad, se registró en primavera (0.51 mm dia -1 ) la menor en verano (0.41 mm dia -1 ), mientras que otoño presentó una tasa de crecimiento intermedia (0.42 mm dia -1 ). Si bien no se encontraron diferencias significativas en las tasas de crecimiento entre verano y otoño, sí las hubo entre primavera y verano y entre primavera y otoño. Se calculó una tasa de crecimiento larvaria 4 días antes de la captura mediante retrocálculo y se la relacionó con la temperatura. Las variaciones en el crecimiento no parecen relacionarse con la influencia térmica.

Putting the pieces together: Recent growth, nutritional condition, and mortality of Engraulis anchoita larvae in the Southwest Atlantic

“…Both through the PCA and through the GLMs results, we observed different relationships among the potentially explanatory variables and the two analyzed indices, RGR and sRD. Larval size and abundance of nauplii were relevant as positive explanatory factors for both indices, coinciding with previous results for this species (Diaz et al, ; Do Souto et al, ; Leonarduzzi et al, ) and other engraulids (Teodósio et al, ). Temperature and appropriate food availability are the main environmental variables that usually correlate with larval growth rates (Buckley, Caldarone, & Ong, ).…”

“…The linear model fitted to the E. anchoita larvae SL (mm)‐age (days) data was appropriate, as we worked with larvae of the first stages of life and without the presence of juveniles. In all areas, the slopes were similar to those recorded in the previous studies for larvae of the same species (Brown, Leonarduzzi, Averbuj, & Livore, ; Leonarduzzi et al, ). When analyzing the results of the DG, RGR, and sRD indices per day, larvae with higher otolith growth rates occurred at different locations than those with the highest sRD indices.…”

Sagittal otolith microstructure, early growth and development of Coilia ectenes in the Yangtze Estuary, China

“…The radius of the PD-band in our study is similar to the radius of the hatching check observed in otoliths of Engraulis japonicus [22] and Engraulis anchoita [33]. A wide band has been observed between the hatching check and the first regular growth increment in otoliths of E. japonicus [22], Anchoa mitchilli [23] and Engraulis ringens [34], similar to the WL-area that we observed in otoliths of C. ectenes.…”

Reproductive success of the Argentine anchovy, Engraulis anchoita, in relation to environmental variability at a mid‐shelf front (Southwestern Atlantic Ocean)

“…Buckley and Durbin (2006) observed strong correlations between copepod biomass and growth rates of cod and haddock in Georges Bank, and concluded that rapid larval growth may be a necessary but not sufficient requirement for a strong year class. Maximum growth rates for E. anchoita larvae occur during spring (0.51 mm day À1 ) rather than summer or fall (0.4 and 0.42 mm day À1 , respectively) (Leonarduzzi et al, 2010), in coincidence with the highest phytoplankton and zooplankton abundances. The tight coupling between chlorophyll concentration at MSF and small copepods abundance suggest that satellite-retrieved chlorophyll data, which are easily accessible, may be a good predictor of food availability for larval E. anchoita on the Buenos Aires province shelf.…”