Gianfranco D’Onghia

Exploring Relationships between Demersal Resources and Environmental Factors in the Ionian Sea (Central Mediterranean)

The relationships between the abundance of demersal resources, environmental variables, and fishing pressure in the north-western Ionian Sea in the last two decades were evaluated. Data on the density collected during seventeen trawl surveys carried out from 1985 to 2005 were used. The following species were considered: Aristaeomorpha foliacea, Nephrops norvegicus, and Parapenaeus longirostris for crustaceans; Merluccius merluccius, Phycis blennoides, and Mullus barbatus for teleost fish. The recruitment index was also considered for N. norvegicus, P. longirostris, M. merluccius and Mullus barbatus. Six candidate models were evaluated for each density and recruitment data set either combining fishing effort with global (NAO) and regional (SST and precipitation) climatic indices, or models separately involving fishing effort, NAO, or regional climatic indices as the only predictive variable. Model selection was carried out using an information-theoretical approach that applies Akaike’s Information Criterion (AIC). High changes over time were observed for the density data and recruitment indices in each species. Apart from hake abundance and recruitment data, for which a clear positive relationship with the NAO index alone was detected, the changes observed in the other species seem to be the consequence of the interaction between bottom-up effects linked to changes in physical environment and top-down ones due to the fishing pressure.

Review of the literature on age and growth of grenadiers in the Mediterranean and new data on age of Trachyrincus scabrus (Macrouridae) in the Ionian Sea

This paper reviews the existing literature on the age and growth of grenadiers in the Mediterranean Sea and provides new data on ageing of Trachyrincus scabrus in the North-western Ionian Sea (Central Mediterranean). Most studies have been carried out through otolith readings. Seasonal otolith formation also appears to be a general trend in grenadier fish in the Mediterranean even though it seems to be related to fluctuations in feeding and activity patterns. From examined literature age ranges of macrourids in the Mediterranean Sea varied from young-of-the-year (age 0) to a maximum ages of 23 years. There is a general agreement on the growth pattern of the species in the different geographic areas. T. scabrus was collected in the North-western Ionian Sea at depths between 400 and 1200 m during four seasonal trawl surveys. The minimum and maximum sizes of the whole sampled population were between 58 and 217 mm PAL. Otoliths were removed from 216 specimens. Backcalculation was performed and a maximum age of 10 years was determined. The following von Bertalanffy growth parameters were estimated for the whole sampled population: L∞ = 247.44 ± 8.39 mm PAL; k = 0.125 ± 0.010/year; t0 = −1.921 ± 0.127.

Cold-water coral communities in the Central Mediterranean: aspects on megafauna diversity, fishery resources and conservation perspectives

In the last two decades, many new living cold-water coral (CWC) sites throughout the Mediterranean basin have been discovered and investigated. As part of oceanographic cruises, using ROVs and towed cameras, and trawl and longline surveys as well as records from fishermen, a belt of CWC communities has been identified along the Apulian continental margin (Central Mediterranean). The most investigated CWC communities are those of the Santa Maria di Leuca (SML) CWC province (northern Ionian Sea) and Bari Canyon (BC) (southern Adriatic Sea). These communities are mainly structured by the habitat-former species Madrepora oculata and, to a lesser extent, by Lophelia pertusa together with Dendrophyllia cornigera, solitary species, such as Desmophyllum dianthus, black coral, such as Leiopathes glaberrima, sponges (e.g., Pachastrella monilifera, Poecillastra compressa), serpulids, boring clams and colonies of bryozoans. CWC sites are biodiversity hot-spots, that act as “Essential Fish Habitats” for commercial species and through the spill-over effect might contribute to the renewal of stocks in neighbouring fishing grounds, providing ecosystems’ goods and services. Despite their particular features, CWC areas along the Apulian slope are impacted by different anthropogenic activities. Fishermen operate close and around these areas with the aim of obtaining greater catches and sizes of commercial species. Although there are many conservation proposals for CWC habitats and a Fisheries Restricted Area established for Santa Maria di Leuca CWC province, human pressure is still very strong, due to the lack of adequate conservation measures. An effective system of monitoring, control and surveillance will be fundamental to meet the conservation objectives and to reach the Good Environmental Status as part of the Marine Strategy Framework Directive.

Fishery resources: between ecology and economy

The complexity in the management of marine biological resources is due to the manifold variables concerning environmental phenomena, technological aspects and socio-economic problems as well as the uncertainties in the assessment of stochastic processes related to the exploited populations. After a short review of the state of art at world level, the authors focus on the Mediterranean and Italian seas providing information on global capture production of fishery resources and economical aspects of fishing activity, raising the need for a management approach that should be robust with uncertainties, suitable for multi-species fisheries and that meets ecosystem objectives. In this respect, the authors report the main recommendations of the Code of Conduct for Responsible Fisheries and measures indicated in the Council Regulation (EC) 1967/2006 and Marine Strategy Framework Directive.

Regional morphology and mucus composition in the urogenital papilla skin of the blackbelly rosefish Helicolenus dactylopterus (Delaroche, 1809)

Blackbelly rosefish Helicolenus dactylopterus is a zygoparous fish whose males are equipped with the copulating organ named urogenital papilla (UP). This study deals with the morphology and the glycoconjugate pattern of the UP epidermis, which is the male tissue interacting with the female internal body during copulation. The carbohydrate content was studied by means of conventional and lectin histochemistry. The epidermis was shown to be a stratified cuboidal epithelium and to exhibit characteristic intraepithelial pits in the apical zone. The mucous cells are scattered in the epidermis. The epidermal cell layers and their thickness as well as the size of mucous cells varied along the UP. Conventional histochemistry showed that the mucous cells contained i) only neutral glycoproteins in the basal zone; ii) both neutral and acidic non-sulphated glycans as well as only acidic non-sulphated or sulphated glycoconjugates in the intermediate zone; iii) neutral and sulphated glycoconjugates in the apical zone. The mucous cells in the basal region expressed O-linked (mucin type) glycans terminating with αGalNAc, Galβ1,3GalNAc which could be α2,3-linked to sialic acid, and high mannose type N-linked glycans terminating with fucose, lactosamine, and sialic α2,6-linked to galactose/N-acetylgalactosamine; terminal Gal and terminal/internal GlcNAc were also found. The mucous cells in the intermediate zone lacked Galβ1,3GalNAc and showed less terminal α2,3-linked sialic acid, lactosamine, fucose, galactose, and internal N-acetylglucosamine residues. In the apical region, mucous cells only exhibited O-glycans terminating with GalNAc and N-acetylglucosamine. The demonstrated region-specific differences in the UP skin provide new insights into the reproductive biology of fishes with internal fertilization.