Estimation of age and growth of juvenile hakes (Merluccius merluccius Linneaus, 1758) of the Bay of Biscay and Great Sole by means of the analysis of macro and microstructure of the otoliths

The growth of juvenile and adult European hake from the Bay of Biscay and the Great Sole were studied analysing the sagittal otolith macrostructure and microstructure. The right and left sagittae otoliths were statistically symmetric in all studied dimensions. In the nucleus, 65 Daily Growing Increments (DGI) were identified. In the samples analysed a growth rate of 0.61 mm day−1 and a total length of 22.2 cm at the end of the first year were estimated. The comparative analysis of the results from several authors on hakes from similar areas showed that the growth rate obtained by tagging studies was almost half of that estimated by otolith microstructure analyses. These differences were probably due to the different size ranges of hake used in the studies. The increase and decrease of DGI width of three juveniles in Spring–Summer and in September coincided with the rise and fall of the water temperature in the Bay of Biscay and with a bloom of phytoplankton observed in March.