Detecting the occurrence of indigenous and non-indigenous megafauna through fishermen knowledge: A complementary tool to coastal and port surveys.

Marine bioinvasions and other rapid biodiversity changes require today integrating existing monitoring tools with other complementary detection strategies to provide a more efficient management. Here we explored the efficacy of fishermen observations and traditional port surveys to effectively track the occurrence of both indigenous and non-indigenous megafauna in the Adriatic Sea. This consisted mainly of mobile taxa such as fishes, crustaceans and molluscs. Port surveys using traps and nets within 10 major Adriatic harbours, were compared with the information obtained from 153 interviews with local fishermen. Information gathered by traps and nets varied significantly and generally resulted of limited efficacy in exotic species detection. Interviews allowed tracking the occurrence of new species through time and space, providing complementary knowledge at the low cost. This combined approach improves our capability of being informed on the arrival of species of different origin, providing a more rational, improved basis for environmental management and decision making.

Feeding ecology and trophic segregation of two sympatric mesopredatory sharks in the heavily exploited coastal ecosystem of the Adriatic Sea.

The ecological roles and trophic interactions of two commercially important mesopredatory shark species, Squalus acanthias and Mustelus punctulatus that co-occur on the continental shelf of the north-central Adriatic Sea were investigated. Both shark species are dietary specialists, with a significant dietary overlap recorded only during the spring season. They showed different patterns of feeding as they grew: S. acanthias extended its trophic niche with an increase in size, while M. punctulatus developed a more specialized diet. These two sharks partition food resources and reduce niche overlap by foraging at different trophic levels. Mustelus punctulatus is a crustacean feeder, specialized in foraging on scavenging malacostracans frequently found along trawl tracks or on discards in the Adriatic fishing zone. Conversely, S. acanthias prefers small pelagic fishes, which are commercially exploited and in decline. The different foraging strategies adopted by these two species suggest that they should be managed separately. Dietary specialization, direct competition with humans for prey and their higher intrinsic vulnerability make S. acanthias particularly susceptible to the effects of anthropogenic perturbations.

Paranthias furcifer (Perciformes: Serranidae), a new alien fish in the Mediterranean Sea.

A specimen of a creole fish Paranthias furcifer (285 mm total length) was captured in Marina Bay (Croatian coast) in the eastern Adriatic Sea. This is the first Mediterranean record of this species. The possible modes of introduction of species are discussed.