Serranus hepatus is a bycatch species in the Mediterranean trawl fishery for which knowledge on biological features such as otolith morphology is generally poor in the Mediterranean Sea. In the present study, the weight–length relationship, age, growth and ten otolith morphometric variables of this species were investigated in two distant areas, the Eastern Ionian and southwestern Aegean Seas. Isometric growth in weight was defined in both areas. Growth parameters also did not differ between the two study areas. Six of the otolith variables (radius, otolith length, otolith width, otolith area, perimeter and ellipticity) showed a significant relationship with size without significant differences between the two areas. Significant differences between the two areas were only defined for five of the morphometric variables (otolith length, width and area being the most important). Further studies to discriminate between potential stocks of S. hepatus seem to be necessary, information that is needed for stock identification, stock assessment and fisheries management.

Climate change and heavy anthropic pressures are giving rise to important modifications in the rocky benthic communities of the Mediterranean Sea. In particular, sponge assemblages have been deeply affected due to the susceptibility of some species to dramatic phenomena such as mass mortalities or widespread variations in the abundance of other species. For this reason, long-term biodiversity monitoring of the sponge assemblages is important for understanding the direction of changes over time. We studied the sponge fauna living off Tricase Porto (Otranto Strait) and compared its composition with the results of a study conducted in the same area 50 years ago. The comparison indicated that the sponge diversity of this area has strongly increased in the last 50 years and a large number of the sponges recorded in the old survey are still present in the recent community. This evidence matches with other results obtained from different localities of the Mediterranean Sea indicating an increase of sponge diversity, possibly due to the present water warming. The description of two new Demosponge species, Diplastrella boeroi sp. nov. and Spirastrella angulata sp. nov., is also provided.

A total of ten coral species are reported from the Capo Rizzuto (Calabria) Marine Protected Area on the Ionian coast of Italy. Two species, Polycyathus muellerae and Paracyathus pulchellus, are new records for the Ionian Sea, a finding that expands their current known distribution range. Eight species are new records for the Ionian coast of Italy. Another species, Astroides calycularis, was identified from a photograph taken in the area, but its presence was not confirmed in the field. The solitary zooxanthellate coral Balanophyllia europaea was found associated with the yellow encrusting coralline alga, Lithophyllum pustulatum, which represents a novel observation requiring further investigation.

The occurrence of Marginaster capreensis in the Taranto seas (Ionian Sea, Italy) is reported. The specimens were mostly found in the Gulf of Taranto (N = 17) and only one specimen in the first inlet of the Mar Piccolo Lagoon. The sizes in the sampled population ranged from 6 to 16 mm.

A single specimen of Bermuda sea chub Kyphosus saltatrix was caught in the Ionian Sea (western Greece). It is the first occurrence of this species in Greek waters and it constitutes its easternmost verified distribution in the Mediterranean. The specimen was a 4-year old male, fully adapted to benthic life and its occurrence adds to the increasing rate of detections of this species in the basin during the last decades.

Several hydroid species live associated with many organisms, including bacteria. Hydroid–bacteria associations were searched for in twenty Hydrozoa species that were collected in the northern Ionian Sea and observed under blue light excitation. Of these, six showed high fluorescence on the outer perisarc, five appeared medium fluorescent, four were slightly fluorescent, and five did not show any fluorescence. Luminous bacteria were isolated and counted from the surface of the fluorescent hydroids. Their association with hydrozoan species could be explained by their feeding activity on the chitinous structures of the perisarc, as previous research on the hydroid Aglaophenia octodonta showed. Moreover, microalgae were always recovered together with luminous bacteria in the strongly, medium and slightly fluorescent hydroids. Further studies will be undertaken to characterize the luminous bacteria isolated from the surface of the examined hydrozoans as well as to better understand whether their interaction with hydroids is only related to chitin utilization or if their coexistence with microalgae in hydrozoans has an ecological meaning.

Three lessepsian fish immigrants—Siganus luridus, Siganus rivulatus and Fistularia commersonii—as well as two alien macroalgae—Stypopodium schimperi and Asparagopsis taxiformis—are reported for the first time from the Messiniakos Gulf (south-east Ionian Sea, Greece). Findings of S. schimperi and A. taxiformis correspond to their westernmost records from Greek waters. Direct field observations showed that S. luridus has established a permanent population, the first to be mentioned in the Ionian Sea taken as a whole. The results increase the total number of marine aliens of the studied area to 14 species, enhancing the assumption that the south-east Ionian Sea is a hot spot on the way of lessepsian species spreading to the west.

A large number of Red Sea species are colonizing the eastern Mediterranean Sea after the opening of the sea-level Suez Canal in 1869, mainly following the Levantine and Anatolian coasts and then spreading westwards, at least in part, by shipping transport of larvae, juveniles, or adult specimens. Two of them are Cerithium scabridum and Fulvia fragilis, well established along the Italian coasts, where new large and stable populations have formed. Some other species, such as Anadara demiri, were accidentally introduced through shipping in our seas and have found good conditions to survive and develop. New distributional and ecological data about these alien molluscs are given and all the species found in association are listed to improve understanding of their living biocoenosis. The presence of a further lessepsian mollusc and of an intentionally introduced species, Brachidontes pharaonis and Ruditapes philippinarum, was also confirmed respectively from Vibo Valentia harbour and from the Gulf of Naples and the Gulf of Taranto. The nomenclature used is based on the CLEMAM Database (last research on 9 January 2008).

The opening of the sea level Suez Canal in 1869 and the increase in commercial shipping routes have led to the colonization of the Mediterranean Sea by Indo-Pacific species. These populations established first along the Levantine coasts and then spread into the central Mediterranean, at least in part by shipping transport of larvae, juveniles or adult specimens. One of these species is Haminoea cyanomarginata, a cephalaspidean belonging to the Haminoeidae, and until now never reported from the Italian seas. In addition, egg-masses of this species have been recorded for the first time in the Mediterranean Sea.

The distribution and population structure of the red shrimp, Aristeus antennatus, were investigated for an unexploited fishing ground in the Greek Ionian Sea (middle-eastern Mediterranean). A total of 8618 specimens, 7273 females and 1345 males was caught during a 12-month survey, from January to December 1997, at depths ranging from 400 to 800 m. Monthly size frequency distributions were analysed using different techniques, resulting in estimates of growth and mortality. Carapace lengths (cephalothoracic lengths, CL) ranged between 12 and 62 mm for females and 9 and 45 mm for males. The mean size of specimens exhibited statistically significant differences in relation to sex and months. Recruitment of both sexes occurred in mid-winter (January). Only the mean size of females seemed to increase with depth. Estimation of the von Bertalanffy growth parameters revealed high k values and a life expectancy of 4 and 5 years for males and females, respectively. A high percentage of specimens bore spermatophores during May and August, indicating that these months were peak breeding periods. Natural mortality rates ranged from 0.55 to 0.70 for females and from 0.62 to 0.79 for males, depending on the method used. Based on its biology and population dynamics, it appears that the red shrimp population in the study area has the potential to support a viable fishery.