Estudios de crecimiento diario en otolitos de larvas de Engraulis encrasicolus L. 1758 en el Golfo de Cádiz (SW Península Ibérica)

This work presents the first study of the daily growth of larvae of anchovy (Engraulis encrasicolus L. 1758) in the coastal area of influence of the Guadalquivir River. Larvae collected in the months of June, August, October and November 2013 by the Spanish Institute of Oceanography in four oceanographic cruises. A Bongo-90 net (mesh size of 1 mm) was used to catch anchovy larvae in horizontal hauls at pre-evening hours. The larvae were frozen in seawater in Eppendorf vials. The standard length (SL in mm) was measured and individual dry weight (DW in mg) was estimated after a lyophilization process. We analyzed growth rings in a total of 309 otoliths in order to estimate the growth of anchovy larvae. For each otolith the area, perimeter, the maximum and minimum diameters and radius, and the extent of the increase in the growth rings were estimated. Some of the results have shown that these morphometric measurements keep a good relationship with the length of the larva, which allows estimating size and age of the larvae from otoliths. We have obtained good relationships (R2 = 90%) for otolith area/standard length in larvae (SL); otolith area/weight in larvae; otolith perimeter/SL and otolith radio/SL. Our results showed a larval growth rate in length of 0.60 mm/day and 0.39mg/day in weight. Finally, we have been found that the width of the rings increases with increasing age of the larva