Age determination and validation on otoliths of the sand-smelt Atherina presbyter (Cuvier, 1829) (Pisces : Atherinidae) from the central-east Atlantic

Abstract

The technique of reading and interpretation of the daily growth increments (DGIs) in the sagittae otoliths was applied to determine the age and growth parameters of Atherina presbyter, a characteristic species of the pelagic-coastal system in the central-east Atlantic. Age reading was validated directly by marking otoliths with strontium chloride (SrCl).The results were based on 201 valid readings of monthly samples obtained between June 1990 and December 1991 in coastal waters of the Canary Islands. The analysed specimens ranged in size from 23 to 104 mm. total length (TL) and in age between 1 and 15 months.The growth parameters of A. presbyter were estimated by the fit of the Von Bertalanffy growth function and gave an asymptotic length (L-infinity) of 106 mm that corresponded to a maximum weight (W-infinity) of 9.0 g, and a growth constant (k) of 2.511. The maximum size obtained and the duration of the A. presbyter life cycle in Gran Canaria were estimated as being smaller than those given for this species in more northern latitudes. The size-age relationship estimated in the present study from the daily growth, showed discrepancies with the one obtained in the same study area by other authors using annual mark readings. The annual marks appeared to indicated approximately double the age compared to the daily increments.