Age and growth of blue-mouth, Helicolenus dactylopterus (Osteichthyes: Scorpaenidae), in the western Mediterranean

Abstract

Helicolenus dactylopterus was studied from 15 bottom trawl cruises carried out between 1991 and 1997 along the Iberian Mediterranean coast. Age and growth of this species were determined for two different areas, the Alboran Sea and the Balearic Sea, characterised by distinct oceanographic and geomorphological conditions. The length (TL), weight (TW), and sex of 3093 individuals were recorded, and sagittal otoliths were collected in subsamples selected to cover the size distribution of both sexes in each area. Marginal increment analysis of specimens between 1 and 4 years old suggested that a single annulus was formed each year. The location of the first annulus was also validated by means of daily growth increments in the otoliths. The fish length range was between 3 and 36 cm in the Alboran Sea and between 2 and 33 cm in the Balearic Sea, which corresponded to individuals between 0 to 30 years old and 0 to 24 years old, respectively. However, 50 and 70% of the studied population in each area were between 0 and 3 years of age. The growth parameters obtained from the age–length relationships showed higher differences between sexes than between areas. In both areas, the maximum age observed and the predicted lengths of males were greater than those of females. The von Bertalanffy growth equation was TL=27.1(1−exp(−0.12( t+2.65))) for females and TL=32.3(1−exp(−0.09( t+3.31))) for males in the Alboran Sea, and TL=27.0(1−exp(−0.16( t+1.62))) for females and TL=32.5(1−exp(−0.10( t+2.62))) for males in the Balearic Sea.