Differences between the sagitta, lapillus and vertebra in estimating age and growth in juvenile Mediterranean dolphinfish (Coryphaena hippurus)

The otoliths (sagittae and lapilli) and the vertebral centra were evaluated as ageing structures in dolphinfish age 0 juveniles (17.2-72 cm FL) caught in the seasonal small-scale fisheries of Majorca and Sicily (western and c entral Mediterranean). Different structure preparation techniques were also tested. Mounting and polishing lapilli for preparing frontal sections requ ired significantly less processing time than for the sagittae. The incremen ts in lapillus were clearly visible from the primordium to the otolith marg in, whereas the intermediate zone in the sagittae was more opaque and preve nted the detection of all the increments. The back-calculated hatchdates fo r otolith ages showed a good correlation with the species reproduction in t he area and provided indirect validation for the age determination. The ver tebrae centra showed increments with higher periodicity than seasonal. A te st of symmetry on the ages derived from the sagitta and vertebra of the sam e fish indicated that the vertebra significantly underestimated the age. Co nsidering the structure processing time and increment definition, as well a s the age-length relationships obtained, it was concluded that the lapilli were the best ageing structure for juvenile dolphinfish. However, validatio n experiments should be carried out before the accuracy of this method can be determined.