Population dynamics and distribution of Eledone cirrhosa (Lamarck, 1798) in the Southern Tyrrhenian Sea (Central Mediterranean)

The present study reports abundance and biomass indices, biological parameters, spatial distribution and population dynamics of the horned octopus Eledone cirrhosa (Lamarck, 1798) in the Southern Tyrrhenian Sea. Data come from two series of trawl surveys (MEDITS and GRUND) carried out from 1994 to 2004. Overall a total of 1278 specimens of E. cirrhosa were caught. By sampling in different bathymetric strata biomass and density indices were calculated for each survey. The highest mean density values were observed in the 101-200 m depth range. Comparing the annual MEDITS and GRUND median length, no significant differences over time were observed. From the resolution of the Medits length frequency distribution (LFDs) with Bhattacharya's method, three groups were identified:recruits, young spawners and old spawners. Length frequency distribution derived from GRUND surveys showed two groups: recruits (juveniles in the autumn period) and adult individuals. Growth parameters obtained in this study were similar to those reported from other areas of the Mediterranean Sea. This result could be due to differences in the range of sizes sampled, the methodology applied and the different characteristics of the study areas. The yield-per-recruit model appeared to be in a state of slight overfishing.