Programma della conferenza

Fishery is considered one of the human activities most responsible for marine habitat fragmentation and loss. However, while the impacts of large-scale fisheries have been largely studied, the potential impact of small-scale fisheries (SSF) on benthic habitats is more often presumed than assessed, with quantitative information still largely lacking. To contribute to fill this knowledge gap, we carried out a fine-scale assessment with the collaborative involvement of local artisanal fishers operating within the Marine Protected Areas of Torre Guaceto and Porto Cesareo, in the Southern Italy. Through in situ landing photo-sampling, we characterized both the sessile benthic bycatch and the commercial catch components of 146 fishing operations, thus comparing the results across the different habitats (e.g. seagrasses and coralligenous) representing the fishing grounds. Our findings show that the benthic bycatch is, on average, the 39% of the total catch (in terms of abundance), representing a concerning and non-negligible fraction.

To shed new light on the role of the SSF in the loss of habitat, we combined data on the bycatch of two habitat-forming species (Axinella cannabina and Posidonia oceanica) with those on the fishing effort, to quantitatively assess habitat loss driven by SSF. Knowledge on fishing effort is fundamental to develop ad hoc regional management strategies to promote eco-sustainable local fisheries. The achievement of the 30% target of the EU’s Biodiversity Strategy will not be reached in absence of careful monitoring and assessment of SSF.

Marine Protected Areas (MPAs) effectiveness can be measured as capacity to conserve and, at meantime, provide natural resources to local populations. The effects of the disturbance produced by Small Scale Fishery (SSF) on fish community of MPA “Parco Sommerso di Gaiola” (Gulf of Naples, South Tyrrhenian Sea) were investigated.

The fishing grounds were divided in three areas: inside or close the MPA, at the West and at the East outside the MPA. In each area, population structures of species from SSF catches and from visual census surveys were compared. Statistical analyses were carried out on percentages of small, medium and large individuals to test for differences in population structures among areas; in addition, “capturability” analyses (sensu: Hawkins et al. 2007) was estimated for each species to assess the susceptibility of a species to be caught.

SSF catches were characterized by the dominance of medium and large individuals, while a meaningful part of small individuals, mainly outside the MPA, characterized visual census surveys. Statistical analyses showed that population structures from SSF catches were not different in the three areas, while significant differences were detected among visual census surveys. “Capturability” analyses show that conger, sea bass, breams, mullets and amberjack are the commercial species more likely to be caught.

Results suggest how SSF activities affect fish community structures. The exploitation of the commercial fishes, mainly selecting medium and large specimens, determines differences among population structures. In fact, from visual census observations it was evident that big sized specimens of commercial species were present inside the MPA and almost absent outside. These observations lead to conclude that MPA “Parco Sommerso di Gaiola” is effective in conserving well-structured fish populations despite its location in a strongly anthropized area.

To identify which prey are at risk due to the invasion of blue crab (Callinectes sapidus) in the Mediterranean Sea, we investigated its feeding behavior and preference for different native Mediterranean bivalve species in a mesocosm experiment conducted withing the project eINS - Ecosystem of Innovation for Next Generation Sardinia (CUP F53C22000430001- MUR Grant Assignment Decree No. 1056).

No-choice prey size and video-recorded prey choice experiments were designed to test the following null hypotheses: i) prey mortality rates do not vary when prey species are provided singularly nor with prey size; ii) the predator does not have preferences when prey are provided singularly; iii) prey consumption rates do not vary among species; iv) manipulating, consuming and handling times do not vary among prey species.

Our results indicate that adult male C. sapidus exhibit a cyclic feeding/resting behavior and show a preference for the commercially exploited native clam, Ruditapes decussatus, followed by Mytilus galloprovincialis and Cerastoderma glaucum, either when provided alone or in combination with other prey. We also estimated that an adult male crab could consume up to 2.6 kg of clams per month during the spring and summer. We also anticipate that the preference of C. sapidus for R. decussatus, a vital commercial species in lagoons along the Italian coastline, will have severe consequences for the lagoons’ trophic webs and the local economy.

Aquaculture is one of the main vectors of non-native species (NNS) transport in the Mediterranean. We used farmers’ local ecological knowledge as an information source to study the presence and effects of NNS in mollusks’ farms in the Adriatic Sea. Study was conducted in 2023 through questionaries with representatives of 24 mussel and 10 oyster farms along Italian Adriatic coast. Most farmers (75% mussel and 90% oyster) knew what NNS are, however, they were aware only of the polychaete Polydora, the ascidian Clavelina oblonga, and the blue crab Callinectes sapidus, and could not indicate other NNS. Rather they could mention the higher taxonomic categories to which non-native organisms belong. The most quoted were ascidians, barnacles, and hydrozoans. From the beginning of their activity, farmers observed the appearance of new ascidians and hydrozoans and an increase in abundances of nemerteans, barnacles, ascidians and Polydora. They claim that these organisms eat or harm molluscs and reduce their marketability. Moreover, farmers were interviewed about the mollusks’ translocation operations they perform. Besides locally producing their own seed, farmers acquire seeds from hatcheries in Italy, Greece, and France, and sell seed to other farms in Italy, Spain and France. Only two mussel farms buy adults for re-immersion and further growth, from Italy and France. Conversely, most mussel and few oyster farms sell their adult mollusks for re-immersion in other farms in Italy, Spain, and France. All these common farming operations might have been responsible for the import of new organisms and could contribute to their further spread in the Adriatic and the Mediterranean. Measures should be taken in collaboration among aquaculture industry, scientists and management bodies to train farmers in recognizing important non-native and pest species and develop procedures for their reporting and undertaking of management measures for the containment of their spread.

The infraorder Astacoidea is one of the most particular taxa from a conservation viewpoint, including some threatened species while others have negative impacts on habitats where they are introduced, establishing self-sustaining populations with possibilities to spread widely. Although the ancestor of Astacoidea colonised inland waters in the Triassic Period some living species inhabiting freshwaters have retained the ability to tolerate high salinity levels as well, and the brackish habitat colonization seems to be quite evident in some introduced crayfish. This phenomenon needs further investigations to understand whether crayfish can adapt to transitional waters, using them either as new elective habitats or as biological corridors. This possibility raises concern for conservation biology and no native species management, with specific regard to: 1) crayfish’s transport and introduction; 2) the increasingly frequent records in transitional waters; and 3) alien threats’ control and management in coastal habitats. Furthermore, here we present for the first time a record of Procambarus clarkii in marine ecosystems for the central Italy coast. Even if the impact on the newly colonised transitional habitats (such as river mouth and temporary wetlands) is not evident yet, the possibility of consequences on these fragile ecosystems seems certain, since they are strategic areas for (i) limicolous birds and endemic fish, and (ii) areas with important economic activities such as fisheries and aquaculture.