Distribution and some biological parameters of the red gurnard, Chelidonichthys cuculus (Actinopterygii, Scorpaeniformes, Triglidae) in the north-central Adriatic Sea

Background. Red gurnard, Chelidonichthys cuculus (Linnaeus, 1758), is distributed in the Mediterranean Sea, Black Sea, and in the eastern Atlantic Ocean from Norway to Mauritania, although it is rarely found in the North Sea and on the Norwegian shelf. The aim of this work was to conduct a comprehensive study of red gurnard in the Adriatic Sea on selected aspects the population biology and some of its environmental implications. Materials and methods. The sampling covered the entire subdivision GSA17 (north-central Adriatic Sea) and it was based on several bottom trawl surveys of MEDITS and GRUND projects from 2000 through 2009. Biometric parameters, as well as the spatial- and depth distributions were analyzed. The parameters such as the length–weight relation, sex, gonad maturity stage, and the stomach content were determined on a subsample of 539 specimens collected seasonally (summer and autumn–winter) within 2007–2009. The data were processed statistically. Results. Chelidonichthys cuculus was mainly distributed in the central Adriatic. Juveniles showed a distribution in shallower waters while adults tended to migrate towards the Croatian coast at greater depths. The total length of the fish sampled ranged from 40 to 303 mm (TL). We assumed the length of 100 mm as a threshold separating juveniles from adults and the length range of 170–190 mm as the maturity size for females and males. Isometric- and allometric growth patterns were showed for the juveniles and the adults, respectively. The diet was based almost exclusively on crustaceans (IRI% > 98%) and it did not change upon reaching the sexual maturity. Chelidonichthys cuculus should be considered a specialist predator feeding mostly on necto-benthic lophogastrids (IRI% > 72%). Conclusion. This work constitutes an attempt to summarize some environmental and biology aspects of the red gurnard in Adriatic population: differences in depth distribution and growth were found between juveniles and adults but not in diet. Males and females showed differences in growth parameters. Extending the studied area and collecting data of red gurnard in the main areas of production should help in better understanding the biology and dynamics of this species.