Biological monitoring of wild thicklip grey mullet (Chelon labrosus), golden grey mullet (Liza aurata), thinlip mullet (Liza ramada) and flathead mullet (Mugil cephalus) (Pisces: Mugilidae) from different Adriatic sites: meristic counts and skeletal anoma

We observed a total of 2169 individuals, 79% of which were fry and the remainder sub-adults, collected during the seasonal migration in freshwater (spring and autumn 1997) by purse-seine. Chelon labrosus accounted for 18% of the samples, Liza aurata 24%, Liza ramada 22% and Mugil cephalus 36%. Fish were sampled in two Adriatic sites, Sacca di Goro (northern Italy, Po River delta) and Lake Lesina (southern Italy). Other samplings from Tyrrhenian Sea (Fiumicino, Tiber river mouth) and from an aquaculture facility (Grosseto) were used in order to obtain additional information on skeletal plasticity of Mugilidae. Observations included meristic counts and skeletal anomalies and some multi-parametric analyses were performed on the data set. The results showed significant differences among the type and rate of skeletal anomalies observed in the fish samples: as far as Adriatic samples are concerned, higher malformation charge was observed in the Sacca di Goro individuals than in Lesina ones. Further, L. aurata showed a non-specific skeletal pattern and the lowest frequency of deformed individual (8.6% of total observed individuals), unlike C. labrosus, L. ramada and L. aurata. So, these Mugilidae species resulted to be differently affected by skeletal anomalies according to the sampling site.