Giandomenico Ardizzone

Seagrass meadows (Posidonia oceanica) distribution and trajectories of change

Posidonia oceanica meadows are declining at alarming rates due to climate change and human activities. Although P. oceanica is considered the most important and well-studied seagrass species of the Mediterranean Sea, to date there has been a limited effort to combine all the spatial information available and provide a complete distribution of meadows across the basin. The aim of this work is to provide a fine-scale assessment of (i) the current and historical known distribution of P. oceanica, (ii) the total area of meadows and (iii) the magnitude of regressive phenomena in the last decades. The outcomes showed the current spatial distribution of P. oceanica, covering a known area of 1,224,707 ha, and highlighted the lack of relevant data in part of the basin (21,471 linear km of coastline). The estimated regression of meadows amounted to 34% in the last 50 years, showing that this generalised phenomenon had to be mainly ascribed to cumulative effects of multiple local stressors. Our results highlighted the importance of enforcing surveys to assess the status and prioritize areas where cost-effective schemes for threats reduction, capable of reversing present patterns of change and ensuring P. oceanica persistence at Mediterranean scale, could be implemented.

Depth-size distribution pattern of Parapenaeus longirostris (Lucas, 1846) (Decapoda) in the central Mediterranean Sea

ABSTRACT The bathymetric distribution pattern of the rose shrimp Parapenaeus longirostris (Lucas, 1846) was analyzed in order to understand the life cycle and migratory behavior, and to construct the growth curve. Five research cruises were carried out in the central Mediterranean Sea (Latium, Italy). Parapenaeus longirostris was captured between 100-m and 508-m isobaths and the highest abundances were observed mainly between 150-m and 350-m isobaths. Recruitment of new generations to the epibenthos essentially occurred between 100-m and 180-m isobaths during the summer. A multivariate ordination method (factorial analysis of correspondence) was used to describe the relationship between the length of the shrimp and the depth. The benthic fraction of the population appeared to be linked to a migratory movement from the middle shelf towards the continental slope. By estimating the parameters of the Von Bertalanffy equation, it was found that the growth of males appeared slower than that of females. The life span of each generation time was about two years.

Incidence of lessepsian migrants on landings of the artisanal fishery of south Lebanon

In the last decade, a growing amount of evidence incorporated by several authors as signals of global changes, defined a trend of expansion of thermophilic species in the Mediterranean. This phenomenon is markedly shown by the spread of some non-indigenous fish beyond their natural limits and by their success in the new colonized areas. The incidence of those non-indigenous fish in the catch composition of artisanal fishery of Tyre (South Lebanon) was investigated for the first time using both official data and daily landing site surveys. The explored fleet consisted of 250 small vessels (4–10 m length) with old and not very powerful engines, and about 400–550 fishermen at the end of 2005. Most of the fleet used different types of bottom standing gear, such as trammel nets, set gillnets and bottom longlines, whereas purse seines and other fishing gear (floating longlines, traps) were used less frequently. Landing was composed by a great number of species, many of which were Lessepsian migrants. We recorded a total of 25 Lessepsian species, representing 17 families and composing 37% of the total landing by weight. Some of these non-indigenous species have become important components of local fisheries in the area.

Biology, spatial distribution and population dynamics of Lepidotrigla cavillone (Pisces: Triglidae) in the Central Tyrrhenian Sea

Abstract Specimens of Lepidotrigla cavillone (the large-scaled gurnard) were collected in the Central Tyrrhenian Sea during trawl surveys carried out in April–May and September 1985, 1986, 1987, 1994, and in October 1995. The species was fished between 30 and 200 m depth. A significant size-depth relationship (p

Diel feeding periodicity and daily ration of shelf break fish species

The evaluation of the daily ration and feeding periodicity in a Mediterranean demersal fish assemblage under natural conditions is presented. Data were obtained during four trawl surveys conducted on the shelf-edge of the central Mediterranean Sea. Recently, researchers have begun to consider this area an essential fish habitat due to its extremely high productivity and diversity. The species which typified the assemblage were the fish Macroramphosus scolopax, Lepidotrigla cavillone, Mullus barbatus, Serranus hepatus, Argentina sphyraena and Glossanodon leioglossus. Fish were collected at three hour intervals throughout four 24 h sampling periods representing annual seasons. The study was based on the analysis of catch data and stomach fullness per setting time. Results show significant variation of feeding periodicity among species within daytime. The amount of food consumed daily, calculated according to the Elliott & Persson model, is compared to the patterns reported in literature for Atlantic fish species with similar trophic habits. Higher values of daily consumption could be related to the reproductive period for most of the above mentioned species.

Polychaetes of an artificial reef in the central mediterranean sea

The development of a polychaete community over five years on a man-made reef was analyzed. The reef was composed of 280 concrete blocks (2 × 2 × 2 m) and located in the Tyrrhenian Sea (Italy) 1.5 miles offshore and 12–14 m deep. Sixty-three species were collected—serpulids, nereids and cirratulids being the most abundant families. Ordination by Principal Components Analysis (PCA) technique showed three main stages in the colonization process: a pioneer phase, when mainly serpulids (Pomatoceros triqueter, P. lamarckii, Hydroides pseuduncinata) occurred; a second phase, characterized by mussel (Mytilus galloprovincialis) dominance and a more differentiated community structure with a lot of new species especially recurring on hard bottom (Serpula concharum, H. dianthus, Ceratonereis costae); and a third phase, with an alteration of the substratum through soft deposits and the polychaete community characterized by also the occurrence of soft bottom species (Heteromastus filiformis, Polydora ciliata, Dorvillea rubrovittata). From the trophic point of view, the structure of the community changed from dominance by filter feeders (97%) to a more differentiated situation with abundant detritic feeders (c. 20%). The rates of immigration and extinction and the colonization curve showed that an actual stable steady-state was not reached.

Daily ration and feeding activity of juvenile hake in the central Mediterranean Sea

We investigated daily ration, feeding rhythms and gastric evacuation rates of juvenile (<16 cm total length) European hake Merluccius merluccius, using stomach samples collected during four 24-hour trawl surveys carried out in 2001-2002 on the continental shelf-break (from 120 m to 160 m in depth) off the western coast of central Italy (central Mediterranean Sea). In each survey 8 hauls of 30 minutes were performed every three hours throughout the 24-hour period to cover the entire diel cycle. Diet of juvenile hake was mostly composed of the euphausiid Nyctiphanes couchii, showing a peak in stomach contents during early morning followed by a daytime decrease. Fullness index (%FI) was generally higher during sunrise when migratory activity ceased and juvenile hake return to the bottom after feeding. Concerning the hake abundance the highest density value was obtained in May during the recruitment period. Two independent daily ration estimates were produced. First, an empirical attempt to estimate the daily amount of food consumed was obtained by back-calculating the fresh weight of euphausiid prey ingested by juvenile hake. Estimated values ranged from 4.96-5.89% body wet weight (%BW). Second, the daily ration was computed applying the exponential gastric evacuation models proposed by Elliot & Persson (1978) and Eggers (1979). Daily ration values obtained using these consumption models produced a considerable (15-20%) underestimation of consumption rate for juvenile hake.

The spiny spider crab Maja goltziana (Crustacea: Majidae) in south Lebanese waters

The spiny spider crab Maja goltziana d’Oliveira 1888, is a species of subtropical Atlantic origin (d’Udekem d’Acoz, 1999). It can be found in the eastern Atlantic Ocean from Portugal to the Gulf of Guinea, as well as in the Canary Islands (González Pérez, 1995). Maurin (1968) reported M. goltziana as a common component of the demersal assemblages over detritic–muddy bottoms along the Morocco and Western Sahara coasts. In the Mediterranean Sea it has been occasionally recorded from the Levantine Basin to the Tyrrhenian Sea and it is considered by far the rarest species of the Majidae family (Zariquiey Alvarez, 1968). Due to its rarity, information on its distribution and ecology in the Mediterranean are scarce. Maja goltziana is a eurybathic species, living on a variety of substrata on the continental shelf and upper slope (Soppelsa et al., 2005). Until now, the few specimens found in the Mediterranean were caught at depths between 20 m and 300 m, on soft bottoms with a muddy component of variable quantity (Pallaoro & Dulcic, 2004). So far no more than 20 specimens have been recorded in the Mediterranean. The first specimen was recorded off the Israel coast in the late 1950s (Holthuis & Gottlieb, 1958). From the 1950s the species was recorded in different sectors of the Mediterranean generally with no more than two specimens (Ramadan & Dowidar, 1972; Koukouras, 1979; Kocatas, 1981; Pastore, 1983; Pipitone & Tumbiolo, 1993; Pallaoro & Dulcic, 2004; Vignoli et al., 2004; Soppelsa et al., 2005; Artüz, 2006). We confirmed the presence of M. goltziana in the eastern Mediterranean Sea, documenting the occurrence of a mature ovigerous female and reporting relatively high abundances for this species in the southern Lebanese waters. A total of 52 specimens of M. goltziana (Figure 1) was collected in the south of Lebanon (Tyre) from June 2006 to May 2007, by means of commercial landing (trammel nets and bottom longlines) and experimental fishing surveys. The gear utilized during the fishing surveys was a nylon monofilament gillnet, 2000 m in length and 4 m in height with a stretched mesh size of 26 mm, designed to target the European hake Merluccius merluccius. All specimens have been caught on a sandy–muddy bottom over a wide bathymetric range, between 80 and 275 m depth. For each specimen we measured carapace length (CL; from the median point between the bases of the rostral spines, to the posterior end of the carapace between the intestinal spines) and carapace width (CW; between the bases of third and fourth main lateral spines of both sides) to the nearest 1 mm. The sex was also recorded. Figure 1. Maja goltziana specimens caught in Lebanese waters.

Phylogeography of the common pandora Pagellus erythrinus in the central Mediterranean Sea: sympatric mitochondrial lineages and genetic homogeneity

ABSTRACT The distribution of the genetic diversity and the population structure of Pagellus erythrinus were analysed using mitochondrial control region sequences and cytochrome b restriction profiles in a total of 128 and 508 individuals, respectively, that were collected from 15 sampling sites in the central Mediterranean Sea and from one site in the Atlantic Ocean. No population genetic structure was detected within the central Mediterranean and thus, the commonly recognized transition zones in the area do not seem to affect population connectivity. The comparison between the Mediterranean samples and the single Atlantic sample suggests weak differentiation between the two basins. Three mitochondrial lineages were identified, each including individuals from almost every sampling site. The haplotype and nucleotide diversity values, mismatch distribution and demographic parameters indicate that the sympatry of these lineages can be ascribed to a period of isolation followed by genetic divergence, population expansion and secondary contact, all of which are likely to be associated with climatic oscillations that occurred during the middle and late Pleistocene.

Feeding ecology of some fish species occurring in artisanal fishery of Socotra Island (Yemen).

The demersal species Lethrinus borbonicus, Lethrinus mahsena, Lethrinus microdon, Lethrinus nebulosus, Lutjanus bohar, Lutjanus gibbus, Lutjanus kasmira, Epinephelus fasciatus, Epinephelus stoliczkae, Carangoides gymnostethus and Euthynnus affinis are important coastal fishes species of the northern coast of Socotra (Yemen), exploited by local fishery. The biology and feeding ecology of these species are poorly known in the area. A total of 1239 specimens were sampled from the main fishing landing site of the island (Hadibo). Total length and weight were measured, stomach contents were analyzed, diet overlap, Fultons Condition index, and trophic levels were estimated. C. gymnostethus, L. microdon and L. kasmira occupied the highest position (T=4.50), L. nebulosus occupied the lower one (TL=3.41). The role of the increasing abundance of small pelagic fish in the diet of many species after the upwelling event is evident, but also different feeding strategies are reported, according to fish ecology.