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In 2001 and 2002 we studied Eurasian otter (Lutra lutra) fish selection in southern Italy by comparing otter diet (805 analysed spraints) with fish availability, estimated by electrofishing. The surveyed river was dominated by cyprinids, particularly by chub (Leuciscus cephalus), roach (Rutilus rubilio) and bleak (Alburnus sp.). Roach and chub were the most common prey recorded in spraints. Otters ate mainly small prey (total length < 90 mm). Chub were widely consumed according to abundance, whilst roach and bleak consumption was not proportionate to their availability. Otters selected roach both in 2001 and 2002 and responded to a decrease in roach availability (–27.3%) by increasing their frequency of consumption rather than switching to an alternative prey. Despite their high abundance, bleak seemed to be markedly avoided by otters. We hypothesized that differences in microhabitat selection may influence the susceptibility of cyprinids to otter predation. The possible effects on fish community...

Biometric evaluation, ovary histomorphometry, plasma 17β‐estradiol (E2) and androgens (A) concentrations were investigated through the gonadal maturation and spawning of the wild chub, Leuciscus cephalus. A lower concentration of plasma E2 was recorded from January (oogonia) to March (previtellogenic oocytes), while estradiol concentrations increased in April, when the ovary mostly contained vitellogenic oocytes. In July, when it was prevalently composed of post‐ovulatory follicles, there was a decline in E2 plasma concentrations. Low concentrations of this steroid remained in the plasma until January, while high concentrations of androgens reached a peak in February and April preceding and following E2. The observed seasonal changes in plasma steroids, reflecting the pattern of follicles size development, were to a large extent consistent with observations made in other cyprinids. Since they define the reproductive cycle of the European female chub, they will be useful in the construction of a maturity s...

The haemoglobin of 26 species (21 Osteichthyes and 5 Amphibia) was examined using electrophoresis and isoelectric focusing. Species‐specific, monomorphic or polymorphic haemoglobin was found and the picture regarding number of fractions, component intensity, migration was heterogeneous for the two different methods. The electrophoretic patterns were made up of single components in Acipenser baeri, one of the two genotypes of Tinca tinca, Carassius carassius, Lepidosiren paradoxa and Bufo viridis; of two fractions in: Calamoichthys calabaricus, A. ruthenus, A. naccarii, A. transmontanas, Leuciscus cephalus cabeda, Anguilla anguilla, Protopterus annectens and Salamandra salamandra; three or more components were found in the remaining species. A comparison of the various species showed varying degrees of taxonomic relationships between the five species of sturgeon, the five mugilids, the two barbs species, the two frogs and between the two salamanders. These species share some common components with...

Genetic variability was assessed in eight populations belonging to the Leuciscus souffla complex and in nine populations of Leuciscus cephalus, sampled in France, Italy and Greece and in one population of Leuciscus lucumonis, endemic to Italy. Twenty‐six enzymatic loci were analysed in order to clarify the genetic relationships, the patterns of colonisation of peri‐Mediterranean area and the taxonomic positions. Results indicate a more ancient penetration of the Leuciscus souffia complex in southern Europe (possibly during the Messinian ‘Lago Mare’ phase of the Mediterranean), whereas L. cephalus and L. lucumonis seem to have quite recently reached these regions (about 1Myr). These evidences are discussed in relation to the two main proposed models of primary freshwater fishes colonisation of peri‐Mediterranean area. In addition, the genetic distance suggests a generic separation between the two complexes. The genus Telestes Bonaparte, is rehabilitated to include members of the Leuciscus souffia ...

A biochemical‐genetic analysis was carried out on five samples of three species of Leuciscus, to verify the genetic divergence between Padanian L. cephalus and L. souffia and to unravel the taxonomic status of a Leuciscus population preliminarly reported as Leuciscus sp., collected from the Adriatic drainage basins and morphologically related to L. lucumonis, a recently described taxon of the Tyrrhenian basins. Both isozymic data on 25 loci and total protein analyses identified Leuciscus sp. as L. lucumonis and showed the high genetic divergence and polymorphism of L. souffia with respect to L. cephalus and L. lucumonis. This study confirms that L. lucumonis is a valid species that inhabits also Adriatic drainage basins and provides conclusive evidence that it is not originated by hybridization. In addition, genetic data fully support the hypothesis of a sharp divergence of L. souffia from congeneric taxa.