Abstract
Studies on Pterois miles growth in the Mediterranean Sea are scant, while otoliths, traditionally used to age Pterois species, present difficulties in sampling, handling and interpretation. In this study a total of 617 P. miles specimens collected from the Cretan and Ionian Seas were aged by reading transverse sections of the third dorsal spine. The monthly evolution of the spine’s edge type (hyaline or opaque) and marginal increment analysis supported the annual formation of annuli. Lionfish age ranged from 0 to 5 years. The length-on-spine radius relationship exhibited a significant change in slope indicating that beyond the estimated inflection point fish growth was slower in relation to spine growth. We applied a multi-stage body proportional back-calculation formula that accounted for this shift in the length-on-spine radius relationship. The comparison of von Bertalanffy growth curves fitted to back-calculated length-at-age data, confirmed the sexually dimorphic growth of Pterois , with males reaching higher mean lengths-at-age. Growth was faster off the island of Crete, which could be attributed to higher temperatures compared to the Ionian Sea. Published growth data from the Pterois invaded areas revealed that the growth performance was significantly lower in the Mediterranean compared to the Atlantic. Finally, an inverse ‘Rosa Lee phenomenon’ was observed, with mean back-calculated length at each annulus formation increasing with age. A hypothesis is formulated asserting that slow growing individuals experience higher mortality (‘faster is better’ hypothesis), which can be attributed to cooler winter temperatures and an associated energetic stress which is inversely related to fish size.