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

Helicolenus dactylopterus was studied from 15 bottom trawl cruises carried out between 1991 and 1997 along the Iberian Mediterranean coast. Age and gr owth of this species were determined for two different areas, the Alboran S ea and the Balearic Sea, characterised by distinct oceanographic and geomor phological conditions. The length (TL), weight (TW), and sex of 3093 indivi duals were recorded, and sagittal otoliths were collected in subsamples sel ected to cover the size distribution of both sexes in each area. Marginal i ncrement analysis of specimens between 1 and 4 years old suggested that a s ingle annulus was formed each year. The location of the first annulus was a lso 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 3 0 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 gro wth parameters obtained from the age-length relationships showed higher dif ferences between sexes than between areas. In both areas, the maximum age o bserved and the predicted lengths of males were greater than those of femal es. The von Bertalanffy growth equation was TL=27.1(1-exp(-0.12(t+2.65))) f or 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. (C) 2000 Elsevier Science B.V. All rig hts reserved.