Selectivity Parameters and Size at First Maturity in Deep-Water Shrimps, Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816), from the North-Western Ionian Sea (Mediterranean Sea)

Selectivity experiments were carried out during trawling targeting deep-water shrimps Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816) (Crustacea, Decapoda, Aristeidae) in the North-Western Ionian Sea (Eastern-Central Mediterranean). Different criteria were employed to analyse maturity; however, the proportion at 50% of retained, mated and mature specimens was always used to indicate the size, expressed as Carapace Length (CL, mm), at first capture (CL_c), mating (CL_sp) and at first maturity (CL_m), respectively. In order to estimate the size at 50% maturity (CL_m) for females of both species, three criteria were adopted. In particular, CL_m was computed for the mature females not considering the presence of spermatophores, for the mature females with spermatophores and for the mature females intersected by the decreasing proportion with size of females without spermatophores. Three diamond stretched mesh codends of 40, 50 and 60 mm were tested using a cover of 20 mm. The 40-mm stretched mesh size (European Union legal size in the Mediterranean) was not selective for the sampled population of each species. The size at first capture (CL_c), calculated in both species for the two sexes combined, increased significantly with mesh size. Even for the mesh size of 60 mm, the size at first capture was still smaller than the sizes at 50% maturity, whatever the criterion adopted. Since the differences between the size at first maturity and the sizes at first capture are greater in A. foliacea than A. antennatus, the former species appears in this respect to be more vulnerable to trawling than the latter.     

Catch Composition on Red Shrimps’ (Aristaeomorpha foliacea and Aristeus antennatus) Grounds in the Eastern Ionian Sea

In the present study, the catch composition and the catch per unit effort (CPUE) by weight and numbers in red shrimps’ (Aristaeomorpha foliacea and Aristeus antennatus) grounds was examined in the southern part of the eastern Ionian Sea, in order to collect important information for the Greek waters, where no deep-water fishery exists. In the depth stratum 500–700 m, the catch of the commercial species represented a high proportion (>70%) of the total catch. Red shrimps and several other commercial species were found in important quantities. The present results suggest the possibility of developing a deep-water fishery in Greece. In such a case, attention should be paid because of the high vulnerability of A. foliacea – the main deep-water fishing resource in the area – to the fishing pressure.     

Effect of codend mesh size increases on the size selectivity of commercial species in a small mesh bottom trawl fishery

The effects of increasing codend mesh size from 11.6 to 25 and 28.7 mm (inside stretched mesh) on the selectivity of greater lizardfish (Saurida tumbil), squid (Loligo sp.), and penaeid shrimp caught by an inshore otter trawling fishery at Nha Trang City, Vietnam were assessed. The proportion of escaping trash fish from the studied codends was also examined. In general, the lengths at 50% retention (L₅₀) of the studied species increased with increasing codend mesh size. L₅₀ values of greater lizardfish for the 25 and 28.7 mm codends were 109.4 and 145.9 mm, respectively. The 11.6, 25, and 28.7 mm codends selected shrimp at L₅₀s of 8.33, 11.86, and 13.92 mm, respectively, and squid (mantle lengths) at 13.1, 36.1, and 41.9 mm, respectively. The mean proportions of escaping trash fish were 0.06, 0.68, and 0.85 for the three codends, respectively. A minimum mesh size of 25 mm is a good compromise between management goals and fishery demands.     

Fishery of the Deep-water Rose Shrimp Parapenaeus longirostris (Lucas, 1846) (Crustacea: Decapoda) in the Northern Tyrrhenian Sea (Western Mediterranean)

The aim of this study is to provide information on the fishing pattern of Parapenaeus longirostris in the northern Tyrrhenian Sea (western Mediterranean), in order to improve the management of the resource in the area. Data were obtained from commercial fishery, covering the period 1991–2002. Catch rates revealed notable inter-annual fluctuation of the P. longirostris landing, probably due to the life cycle of the species. The highest yields (kg per hour of trawl) of the commercial fishery were obtained at depths ranging between 180 and 300 m, the lower ones at depths between 100 and 180 m, where small specimens are more abundant. Commercial catches were characterised by a very low presence of specimens smaller than 20 mm carapace length (CL), mainly due to the deeper localisation of the fishing grounds when compared to the recruitment areas of the species. The size at which 50% of the specimens were discarded by the fishermen was 15 mm CL, while the estimated size at first capture of the individuals caught by the commercial net was 12.4 mm CL.     

Trawl Selectivity Trials on the Deep-water Rose Shrimp (Parapenaeus longirostris) in Sicilian Waters

The selectivity of the traditional commercial bottom trawl net employed in Sicily to catch the Mediterranean deep-water rose shrimp, Parapenaeus longirostris, has been assessed. Two fishing campaigns were carried out in the Strait of Sicily and in the Southern Tyrrhenian Sea, using the covered cod-end method (mesh 20 mm vs. 31 mm). Of a total catch of 11,601 individuals, 23.4% escaped in the cover; the sample length structure from the Strait is unimodal, while that from the Tyrrhenian, polymodal. A logistic curve, fitted with a maximum likelihood criterion, has been used to model the selectivity data, in order to obtain the parameters CL_c50% (50% retention size), SR_75–25% (selection range) and SF (selection factor, i.e. CL_c50%/mesh). The two sets of data, besides a larger selection range for the Strait sample (5.2 mm vs. 2.3 mm), produced very similar estimates (retention sizes of 13.0 mm vs. 12.8 mm CL), fitting the logistic curve well. Almost no shrimp larger than 20 mm does escape from the cod-end; moreover, from the amount of damaged specimens found in the cover, even the evaded shrimps sustain a high fishing mortality. An increase of the present cod-end mesh opening, even above the size required by the EU bylaws (at present, 40 mm stretched) seems necessary for managing the fishery.     

Notes on the distribution and biology of the deep-sea crab Bathynectes maravigna (Brachyura: Portunidae) in the Mediterranean Sea

Data on the distribution and biology of the deep-sea portunid crab Bathynectes maravigna are reported for the Mediterranean Sea, based on several fisheries research surveys. Densities are low and, therefore, biological data are scarce. In the western Mediterranean, the species is much commoner in Alborán Sea than in the Catalano-Balearic Sea. Occurrences are also scarce in the southern Adriatic and northwestern Thyrrenian Sea, as well as in the Ionian Sea. The Alborán Sea and the seas surrounding the southern Italian peninsula are the areas where densities are the highest. The occurrence depth range was found to be 245–786 m, but most of the occurrences took place deeper than 500 m. Sizes ranged between 9 and 51 mm carapace length in males and between 12 and 51 mm in females. Ovigerous females have been only reported in October–December and March–May. Eighty three percent of both males and females are right-handed. Sexual dimorphism was present in cheliped length with males having longer chelae than females. The species appears to be much commoner in those areas where Atlantic influence is the highest.     

Epibiontic and endobiontic polychaetes of Geodia cydonium (Porifera,Demospongiae) from the Mediterranean Sea

Polychaete assemblages associated to the sponge Geodia cydonium were investigated at two sampling sites in the Mediterranean Sea: Porto Cesareo Basin (Apulia) and Marsala Lagoon (Sicily), both characterized by sheltered hydrodynamic conditions. Samples were seasonally performed during 1997, in order to compare the assemblages coming from the two localities studied, considering separately the internal and external tissues of the sponge, and with the aim of evaluating the influence of sponge size on polychaete colonization. The examined sponge is characterized by a peculiar stratification of its tissues: an external thick and hard layer, the cortex, and an internal softer one, the choanosome. Statistical analysis showed that this was the main factor controlling polychaete assemblage, with the internal tissue, less rich and diversified, appearing impoverished with respect to the external layer. A similarity in species composition was observed between sites, even though some differences were evidenced in the abundance of some species, mainly reflecting differences in local environmental conditions. Species richness and density increased with the increasing sponge size. Such a situation is particularly evident at Porto Cesareo, where sponges are covered by an algal layer which is particularly rich on the largest specimens, thus suggesting that most of the species of polychaetes were linked more to the neighbouring environment than to the sponge itself.     

Anthesis effects on Posidonia oceanica (L.) Delile phenology in the Bay of Calvi (Corsica,Mediterranean Sea)

In Posidonia oceanica (L.) Delile, anthesis induces a decrease in the number of juvenile leaves resulting in a significant reduction in the number of leaves on the flowering shoots. All the leaves of the flowering shoots are narrower than the leaves of nonflowering shoots. A modification of the leaf growth also appears in flowering shoots: the oldest leaves are longer and the leaves induced during or after anthesis are shorter. At 10 m depth, in the Bay of Calvi, anthesis lasts roughly 3 months and the flowering is induced 7 months before anthesis.     

Comparative fecundity and oocyte size of Aristaeomorpha foliacea and Aristeus antennatus in the Greek Ionian Sea (E. Mediterranean) (Decapoda: Aristeidae)

Absolute and relative fecundity of 49 ripe gonads (from the cephalic and the abdominal sections of the same specimen) of Aristaeomorpha foliacea and 71 ripe gonads of Aristeus antennatus caught in the Ionian Sea (E. Mediterranean) and their oocyte size were studied. Both average absolute and relative fecundities estimated for A. antennatus were statistically higher than those estimated for A. foliacea; the average absolute fecundity of A. foliacea was 151 936 oocytes/female and that of A. antennatus was 200 472 oocytes/female and the average relative fecundity of A. foliacea was 5477 oocytes/g and that of A. antennatus was 9386 oocytes/g. Fecundity in both red shrimp species is linearly related to carapace length, body and gonad weight, although, the most precise estimation is provided by the relationship of body weight and fecundity. In the present study, the oocyte size (diameter, volume) of both species could be considered very large. In conclusion, A. foliacea shows lower fecundity than A. antennatus, having a lower ovogenetic activity, but it produces larger oocytes. This is in accordance with the highest value of the gonad weight and gonad volume of A. foliacea exhibited in relation to A. antennatus.     

Feeding Habits of Percnon gibbesi (H. Milne Edwards, 1853) in the Sicily Strait

The subtropical grapsid crab Percnon gibbesi (H. Milne Edwards, 1853) is one of the most recent alien decapods found in the Mediterranean, where it was discovered at Linosa (Pelagie Islands, Sicily Strait) in summer 1999. At present, the invasion of this species has been recorded in several other insular localities. We studied the feeding habits of the crab in an attempt to understand its success in the Mediterranean. The morphological characteristics of the chela, the feeding adaptations of the gastric mill and the analysis of stomach contents indicate that P. gibbesi is a strictly herbivorous species, a characteristic not shared with any other large-sized infralittoral Mediterranean crab.     

First geo-marine survey of living cold-water Lophelia reefs in the Ionian Sea (Mediterranean basin)

Abstract Prosperous deep coral mounds including living colonies of Lophelia pertusa together with Madrepora oculata and Desmophyllum dianthus (= D. cristagalli) have been discovered in 2000, by fishery operations on the eastern side of the Ionian Sea. The living coral mounds are located between ca. 300 and 1,100 m on a gently dipping shelf off Apulia at Santa Maria di Leuca (SML), and characterized by a complex seabed topography. Side scan sonar, shallow high-resolution seismics and sampling indicate that these Lophelia-bearing coral mounds colonize quasi-indurate (firmground) Pleistocene sediment. At places live corals were found on Pleistocene coral-hardgrounds. The fauna associated with these Ionian modern coral mounds is less diversified than modern Eastern Atlantic counterparts. The core of living coral mounds colonies is at present located in 500–700 m and is tentatively suggested that their survival is mostly controlled by oceanographic factors. The SML coral banks represent so far a unique example of living Lophelia-bearing coral mounds in the Mediterranean basin.This revised version was published online in January 2005 with corrections to the author name and figure captions 4 and 5.     

New records and uncommon occurrences of deep-water fishes in the Turkish Mediterranean Sea (Osteichthyes)

In monthly surveys carried out between September 2009 and July 2011 in Antalya Bay, five species of fish were found which have hitherto been unknown from the Antalya Bay: Notacanthus bonaparte, Diaphus metopoclampus, Gadella maraldi, Benthocometes robustus and Evermannella balbo. For the latter species it is the first record for the Turkish Seas.     

The vertical distribution of Chthamalus montagui and Chthamalus stellatus (Crustacea,Cirripedia) in two areas of the NW Mediterranean Sea

The Mediterranean Sea is characterised by a small tidal range (0.3–1 m). Despite this, intertidal communities are well established and their upper limits often extend above mean high water level. Organisms living in the intertidal region and in the supralittoral zone rely on both tides and wave action to perform their biological functions. Lack of food, desiccation and predation are common stresses in such a harsh environment. The present study deals with the vertical distribution of two species of intertidal barnacles, Chthamalus montagui Southward and Chthamalus stellatus (Poli), which are the main constituents of the barnacle belt along Mediterranean rocky shores. Previous work, carried out in the Atlantic, showed that where the distribution ranges of the two Chthamalus species overlap, C. montagui is more common in the upper barnacle zone while C. stellatus is dominant lower down. The main aims of our study are: (1) to establish if there is a relationship between position and extension of the barnacle belt on the shore and tidal range and/or wave exposure, (2) to test the hypothesis that in the study areas C. montagui is more abundant than C. stellatus high on the shore, and that the pattern is reversed lower down. Barnacle populations were monitored in summer 1998 in the Gulf of Genoa (Ligurian Sea) and in the Gulf of Trieste (North-Adriatic Sea). The two areas differ in tidal range and hydrodynamism, the former presenting quite strong wave action and a tidal range of 30 cm, the latter having limited wave action and 1 m tidal range. Three shores were randomly selected in each gulf and two transects on each shore. Counts of barnacles in 10 ^* 10 cm quadrats were done at different shore heights along each transect. The data was subjected to analysis of variance. Results showed that a more pronounced hydrodynamic regime corresponded to a shift of the barnacle belt towards the higher shore (Gulf of Genoa), while in more sheltered areas (Gulf of Trieste), the barnacle distribution was confined to the intertidal region. The relative spatial distribution of C. montagui and C. stellatus within the barnacle belt varied locally, even between transects on the same shore, and this obscured the distribution pattern along the vertical gradient. Nevertheless, it was still possible to conclude that at mid and high shore in Genoa, C. stellatus was more abundant than C. montagui, while in Trieste the pattern was reversed.     

Sex-related variability of rostrum morphometry of Aristeus antennatus (Decapoda: Aristeidae) from the Ionian Sea (Eastern Mediterranean, Greece)

Sex-related rostral variability was studied in the aristeid shrimp Aristeus antennatusfrom the Eastern Ionian Sea (Mediterranean). Shrimps were collected on a monthly basis from December 1996 to November 1997 using a commercial bottom trawl in a depth range of 446–728 m. Female relative growth of rostrum proved to be negative allometric both seasonally and in the pooled annual data set. Males on the other hand, showed no or negative correlation of rostrum length with size. Mature males with short rostra dominated in the male population all year around. The appearance of males with long and intermediate rostra during winter, which disappear thereafter in favour of those with short rostra, indicates that rostrum shortening takes place during the end of winter. The increase of mated females during spring supports the hypothesis already addressed by other authors on the function of the male short rostrum in this species mating behaviour. Nevertheless, the paucity, in comparison to other Mediterranean populations, of males with long or intermediate rostra could indicate that for the bulk of the male population, the process of rostrum shortening in the Eastern Ionian Sea occurs outside the geographical locality or depth range sampled.     

Effects of Dredging Activities on Population Dynamics of Posidonia oceanica (L.) Delile in the Mediterranean Sea: The Case Study of Capo Feto (SW Sicily, Italy)

Between 1981 and 1993 a methane pipeline was deployed between Sicily (Italy) and Tunisia. This involved the construction of a pipeline trench, which damaged the Posidonia oceanica (L.) Delile meadow at Capo Feto (SW Sicily, Italy) and disturbed the surrounding meadow. Seagrass growth and population dynamics were examined at different depth ranges and at increasing distances from the construction site outer limit (5, 15, 30, 50 m). Results showed significant differences between the shallow (10±3.3 m) and the deep (20±4.6 m) meadow as well as differences among distances. The age structure of P. oceanica varied along the distance gradient and with depth. The mortality rate decreased with distance from the trench at all depth ranges, showing that the plants close to the excavation suffered a higher level of disturbance. Turnover and annual gross shoot recruitment rate (R_gross) were higher in the shallow portion of the meadow than in the deep range. Forecast of future meadow development (R_net) close to the trench indicates that, if present conditions are maintained, shoot density will be reduced by 50% over the next 6 to 17 yrs.     

First record of Cephalopholis taeniops (Valenciennes) in the Mediterranean Sea

Two specimens of African hind Cephalopholis taeniops (Valenciennes, 1828) are recorded for the first time in the Mediterranean Sea, in the coastal area of Gulf of Syrte, Libya. This finding represents an additional case of a tropical species of fish of West African origin in the Mediterranean Sea.     

Molecular evidence for the occurrence of Contracaecum rudolphii A (Nematoda: Anisakidae) in shag Phalacrocorax aristotelis (Linnaeus) (Aves: Phalacrocoracidae) from Sardinia (western Mediterranean Sea)

Specimens of Contracaecum rudolphii Hartwich, 1964 (Nematoda: Anisakidae) from Phalacrocorax aristotelis (Linnaeus) from the Archipelago of La Maddalena (Sardinia, western Mediterranean Sea) were characterised genetically and compared with C. rudolphii A sensu D’Amelio et al. 1990 and C. rudolphii B sensu D’Amelio et al. 1990 from Phalacrocorax carbo sinensis (Blumenbach) from north-eastern Italy, and with C. rudolphii C sensu D’Amelio et al. 2007 from Phalacrocorax auritus (Lesson) from west-central Florida, USA. The sequencing of the small subunit of the mitochondrial ribosomal RNA gene (rrnS) and by polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) analysis of the same gene and of the internal transcribed spacers (ITS) of nuclear ribosomal DNA (rDNA) allowed the identification of all specimens of C. rudolphii from P. aristotelis as C. rudolphii A. The results confirmed that the definition of genetic markers, following the analysis of nuclear ribosomal and mitochondrial DNA, provides quick and practical diagnostic tools for the detection of the 3 sibling species of C. rudolphii. The occurrence of C. rudolphii in P. aristotelis is reported for the first time from the Mediterranean area, improving the picture of the dispersal patterns of the populations of these piscivorous birds, and confirming the existence of different and isolated populations between the North and South European waters.     

Stability of spatial pattern of fish species diversity in the Strait of Sicily (central Mediterranean)

In this paper, species diversity of demersal fish communities was analysed over an area covering about 45,000 km² of the Italian side of the Strait of Sicily (central Mediterranean). Fish abundance data come from a 10-year series (1994–2003) of experimental bottom trawl surveys carried out within the framework of the international program MEDITS. A simple GIS-based method was proposed to identify areas supporting high or low values of diversity and evaluate their temporal stability. A well-defined spatio-temporal pattern in diversity emerged from the analysis, with some areas of great ecological relevance being identified. Importantly, the greatest diversity within the fish communities was consistently seen at the offshore bank on the western part of the south Sicilian shelf (Adventure Bank). The site also supports high total biomass of demersal resources and shows the presence of species of great concern to fisheries. Results suggest that Adventure Bank represents a priority site for investigating the possibility of innovative management of marine ecosystems and demersal fisheries in offshore zones.     

Molecular Systematics and Phylogenetics of Gracilariacean Species from the Mediterranean Sea

Mediterranean reports of Gracilariaceae species, in particular those assigned to the G. verrucosa complex, were re-examined with the use of molecular tools, in order to verify their systematic position and better understand their distribution. Within this complex, we recognized four distinct taxa: Gracilariopsis longissima, Gracilaria gracilis, Gracilaria longa and a possible new species. The rbcL gene sequences, together with those of other terete Mediterranean entities, were included in a broad molecular phylogeny of the family. The reproductive characters of the studied taxa do not fit completely with published hypothesis on the generic and intrageneric relationships, suggesting that the anatomy of some subgroups should be better characterized.     

Seasonal variations of microphytoplankton assemblages and environmental variables in the coastal zone of Bozcaada Island in the Aegean Sea (NE Mediterranean Sea)

Seasonal changes in the microphytoplankton assemblages were examined in the coastal zone of Bozcaada Island with regard to some major physical and chemical variables. Samples were collected from May 2000 to December 2001 at four stations. A total of 108 dinoflagellates, 102 diatoms, 1 chrysophycean, 3 dictyochophycean, and 1 prasinophycean species were identified and quantified during the study period. Diatoms and dinoflagellates were the most important in terms of species number and abundance. The maximum values of total microphytoplankton were observed at 0.5 m depth (46.2 × 10³ cells l⁻¹ at st. 3) in May as this was the month when the diatom Pseudo-nitzschia pungens bloomed. Chlorophyll (chl) a concentration ranged between 0.08 (August) and 0.78 μg l⁻¹ (February). May was another important month in which chlorophyll a increased (0.41–0.47 μg l⁻¹). Species diversity values (H′_log2) ranged from 1.66 bits (June, 20 m) to 4.11 bits (November, 0.5 m). The increase was attributed to a more balanced distribution of abundance among species. The amounts of nitrate + nitrite (0.6−3.7 μg-at N l⁻¹), phosphate (0.2−0.6 μg-at P l⁻¹) and silicate (0.7−2.5 μg-at Si l⁻¹) were recorded on each sampling occasion. Nutrient concentrations and chl a values of the research area were found to be poorer than those of the many other coastal areas in the northeastern Mediterranean. The mean atomic ratio of nitrogen to phosphorus varied from 1.3 (June) to 12.9 (February). This ratio was lower than the Redfield ratio of 16 for ocean phytoplankton, and phytoplankton was potentially limited by nitrogen for most of the months. The result of this study confirms and emphasizes the oligotrophic nature of the eastern Mediterranean.