Calcareous nannofossil surface sediment assemblages from the Sicily Channel (central Mediterranean Sea): Palaeoceanographic implications

Quantitative analysis of 67 calcareous nannofossil assemblages from surface sediments recovered in a wide area across the Sicily Channel has been carried out in order to improve the interpretation of palaeontological data based on this planktonic group in a key area for Mediterranean palaeoceanographic studies. The investigation focused on three case studies that demonstrate the high potentiality of such a combined approach, taking into account the recent distribution of taxa or groups of taxa on the sea floor and the palaeontological record. The distribution of reworked specimens over the northern Sicily Channel sea floor validates the role of southern Sicily as a source region for reworked nannofossils and the role of rivers as their carrier. Eustatic sea-level fluctuations can be considered to be the main factor that influenced the abundance variations in sedimentary sequences of this area. The distribution of Florisphaera profunda can be explained in terms of topography (positive correlation) and mesoscale oceanographic circulation. In particular, its significant anti-correlation to the amount of chlorophyll-A deduced by satellite imagery validates the use of this species as a proxy for palaeoproductivity reconstructions. Finally, high abundance values of G. oceanica are confined to the westernmost part of the Sicily Channel, coinciding with a water mass salinity minimum. In particular, abundances of up to about 10% were observed in the westernmost part of the African Margin, suggesting the importance of the Atlantic Tunisian Current, whose activity is more pronounced in winter. The comparison of data of this species between 135 and 110 kyr BP, inside and outside the Channel, led us to deduce that the physical transport in almost unmodified waters of Atlantic origin might be the most important factor for its significant occurrence.     

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.     

Fueling Plankton Production by a Meandering Frontal Jet: A Case Study for the Alboran Sea (Western Mediterranean)

A three dimensional biophysical model was employed to illustrate the biological impacts of a meandering frontal jet, in terms of efficiency and persistency of the autotrophic frontal production, in marginal and semi-enclosed seas. We used the Alboran Sea of the Western Mediterranean as a case study. Here, a frontal jet with a width of 15–20 km, characterized by the relatively low density Atlantic water mass, flows eastward within the upper 100 m as a marked meandering current around the western and the eastern anticyclonic gyres prior to its attachment to the North African shelf/slope topography of the Algerian basin. Its inherent nonlinearity leads to the development of a strong ageostrophic cross-frontal circulation that supplies nutrients into the nutrient-starved euphotic layer and stimulates phytoplankton growth along the jet. Biological production is larger in the western part of the basin and decreases eastwards with the gradual weakening of the jet. The higher production at the subsurface levels suggests that the Alboran Sea is likely more productive than predicted by the satellite chlorophyll data. The Mediterranean water mass away from the jet and the interiors of the western and eastern anticyclonic gyres remain unproductive.     

The impact of fisheries on vulnerable habitats: the case of trawling on circa-littoral grounds in the Strait of Sicily (central Mediterranean Sea)

The Council Regulation (EC) no. 1967/2006 introduced the adoption of the 40 mm square-mesh or alternatively a 50 mm diamond-mesh codend for trawlers of EU Member States. In this context, the main aim of the current study was to compare the catch composition of Lampedusa’s shallow-water trawl fishery, in terms of retained and discarded fraction, using the 24 mm square-mesh codend (illegal and supposed unselective) and the 50 mm current diamond-mesh codend (legal and supposed selective). During 2012, 21 hauls were performed, under commercial conditions, with the 24 mm square mesh codend and 27 with the 50 mm diamond mesh codend in an area of the Strait of Sicily at depths from 40 to 80 m. The introduction of a 50 mm diamond-mesh, although not significantly, reduced the CPUEs of retained and discarded fraction compared with the 24 mm mesh. Moreover, for most target species and their size classes (especially immature individuals), the legal mesh recorded a lower mean number of specimens than the banned mesh size. All these advantages aside, the discard of the shallow-water trawl fishery, in Lampedusa, represented a very important part of the total catch (more than three-quarters) by both mesh sizes and a large amount of this was represented by species and habitat of conservation concern. Our results suggest that spatial restrictions, such as no-take zones, could be a more effective management tool to protect this sensitive ecosystem in the area than the technical measures (e.g. reduction of mesh size) imposed today by the EU.     

Ageostrophic Frontal Processes Controlling Phytoplankton Production in the Catalano-Balearic Sea (Western Mediterranean)

Buoyancy-induced unstable boundary currents and the accompanying retrograde density fronts are often the sites of pronounced mesoscale activity, ageostrophic frontal processes, and associated high biological production in marginal seas. Biophysical model simulations of the Catalano-Balearic Sea (Western Mediterranean) illustrated that the unstable and nonlinear southward frontal boundary current along the Spanish coast resulted in a strain-driven frontogenesis mechanism. High upwelling velocities of up to 80 m d^-1 injected nutrients into the photic layer and promoted enhanced production on the less dense, onshore side of the front characterized by negative relative vorticity. Additional down-front wind stress and heat flux (cooling) intensified boundary current instabilities and thus ageostrophic cross-frontal circulation and augmented production. Specifically, entrainment of nutrients by relatively strong buoyancy-induced vertical mixing gave rise to a more widespread phytoplankton biomass distribution within the onshore side of the front. Mesoscale cyclonic eddies contributed to production through an eddy pumping mechanism, but it was less effective and more limited regionally than the frontal processes. The model was configured for the Catalano-Balearic Sea, but the mechanisms and model findings apply to other marginal seas with similar unstable frontal boundary current systems.     

Association patterns and population dynamics of bottlenose dolphins in the Strait of Sicily (Central Mediterranean Sea): implication for management

An understanding of the population dynamics and social organization of cetaceans is essential to manage the influence of anthropogenic activities. In this study, the population size, site fidelity and social interactions of bottlenose dolphins in the Strait of Sicily (Italy) were investigated to provide recommendations for their conservation. Mark-recapture analysis was based on the encounter histories of 103 marked dolphins from 2004 to 2015. The POPAN formulation of the Jolly–Seber model in MARK software was used to estimate the size of the super-population. Site fidelity and social organization were estimated for individuals re-sighted ≥3 times. The estimated population size was 140 (SE = 15.75; 95% CI = 106–164). Dolphins had low site fidelity, and both adults and sub-adults move outside the study area. Females with calves used the area longer than other individuals. Based on our results, dolphins’ home range likely extended beyond the study area. The mean value of the Half-Weight Association Index was low and the preferred association was by casual acquaintance. However, we found a distinct aggregation of post-parturition females during the final 2 years of the study. Therefore, the pattern of association was apparently a response to an ecological requirement, which was the possibility to breed in high productivity waters. Whether these individuals are part of a larger pelagic population is unknown; however, we can conclude that the management of only coastal waters is insufficient for the conservation of dolphins in the Strait of Sicily.     

Anchovy (<Emphasis Type="Italic">Engraulis encrasicolus</Emphasis>) early life stages in the Central Mediterranean Sea: connectivity issues emerging among adjacent sub-areas across the Strait of Sicily

The combined use of field data on anchovy (Engraulis encrasicolus, Linnaeus, 1758) egg distribution in the Central Mediterranean Sea on both sides of the Strait of Sicily (Sicilian–Maltese and Tunisian waters) and Lagrangian simulations were used to assess the pattern of connectivity between these two sub-areas as a result of spawning activity. The field data were collected during ichthyoplankton surveys carried out in summer 2008 and 2010. The simulation runs showed considerable (up to 20%) rates of particle exchange in both directions (from Tunisian to Sicilian–Maltese waters and vice versa). However, considering the typical high mortality rates of anchovy early stages, the actual larval exchange rates across the Sicily Strait are supposed to be significantly lower (<1%), supporting the hypothesis that the anchovy population sub-units in the Strait of Sicily can be considered as separate fish stocks for the evaluation of their optimum exploitation rates.     

On the first record of the genus Octopoteuthis (Cephalopoda: Octopoteuthidae) in the Sardinian Channel (central western Mediterranean Sea)

A specimen of the rare squid genus Octopoteuthis (Cephalopoda: Octopoteuthidae) from 1600 m in the Sardinian Channel (central western Mediterranean) is described. Meristic and morphological data are provided. The specimen was a spent female and details of the reproductive system and implanted spermatangia are reported. Genetic analysis of this specimen and comparison with those available for species in this genus were carried out. Due to issues associated with the taxonomy of the genus Octopoteuthis, it was not possible to identify the specimen to the species level. The taxonomy of the genus is discussed.     

Distribution and abundance of fish larvae in the northern Ionian Sea (Eastern Mediterranean)

The purpose of this paper was to study the spatial distribution, abundance and composition of fish larvae in the northern Ionian Sea. Samples were collected to the 600 m depth with an electronic multinet BIONESS during the “INTERREG Italia-Grecia” oceanographic cruise carried out in March 2000 off the Apulian Italian coast. A total of 46 species of teleost early stages were collected, belonging to 38 genera and 22 families. Over 52% of the larvae identified were mesopelagic species, almost 27% were demersal and about 21% pelagic. A total of 307 myctophids, 69 clupeids and 61 gadid post-larvae dominated the community. Benthosema glaciale (mean 6.1 mm SL) was the most abundant species (21.6%), the most frequent in the samples (28.8%), and dominant in the whole study area (mean 1.4 ind/100 m³). Particular attention was given to the horizontal and vertical distribution and abundance of the three dominant post-larval species: Benthosema glaciale, Sprattus sprattus sprattus and Notoscopelus elongatus. The Pearson coefficient (R = 0.734) showed a high correlation between total zooplankton and fish larval assemblages in terms of spatial distribution abundance values. Regarding the vertical distribution of fish larvae, Sorensen’s index (S = 0.69) showed that fish larvae and total zooplankton abundance peaks co-occurred along the water column.     

Larvae of Barnacles (Cirripedia: Thoracica) in the White Sea Plankton

The barnacle fauna of the White Sea is briefly described. The morphology of barnacle larvae in this water body is comparatively analyzed. The characters important for the larvae identification are given particular attention. A classification key for the naupliar and cyprid larvae of White Sea barnacles is proposed.     

The First Data on Larvae of Trematodes from the Gastropod Hydrobia acuta in the Black Sea

Biology Bulletin - In this work, the first information on the species biodiversity of larvae of trematodes in the gastropod Hydrobia acuta is provided. As result of this research, the species...     

The threadfin bream Nemipterus randalli (Perciformes: Nemipteridae) in the eastern Mediterranean Sea

A total of 30 specimens (73–95 mm standard length) of Nemipterus randalli were collected along the Lebanon coast. This species, a Lessepsian migrant previously misidentified as Nemipterus japonicus , appears to be well established in the Levantine basin of the Mediterranean Sea. The small size and immature status of the specimens of N. randalli collected from the Lebanon coast indicate recent successful recruitment.     

A new species of Diplecogaster (Actinopterygii: Gobiesocidae) from the Mediterranean Sea

Diplecogaster umutturali sp. n. is described from five specimens, ranging from 9.5 to 26.9 mm in standard length. This clingfish is known to occur only at three localities along the northern Levant coasts, eastern Mediterranean Sea and is the third known species of the genus Diplecogaster in the Mediterranean and Black Seas. The species is distinguished from all its congeners in having a small snout, short caudal peduncle, large eyes, short anal fin and upper attachment of gill membrane opposite the 7th-8th pectoral ray. Diplecogaster umutturali sp. n. shows a 5.3% genetic divergence from its close relative D. bimaculata at the cytochrome oxidase I locus (COI).

http://www.zoobank.org/urn:lsid:zoobank.org:pub:376298FE-C8A7-44BB-9B12-721E41D7F355     

A new species of Caprella (Crustacea: Amphipoda) from the Mediterranean Sea

A new caprellid amphipod, Caprella tavolarensis n. sp., is described based on specimens collected from a Posidonia oceanica seagrass meadow at the Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, Mediterranean Sea). The species is close to Caprella liparotensis, but can be clearly distinguished by smaller size, presence of a short rostrum, body elongate and dorsally smooth, absence of serrate carina on the basis of gnathopod 2 and pereopods, mouthparts scarcely setose, absence of fine setae on peduncle of antenna 1 and absence of swimming setae on antenna 2. The number of caprellid species reported from the Mediterranean Sea has increased from 23 (1993) to 41 (2010), consequently, further taxonomical studies should be addressed to properly estimate the total amphipod diversity in the Mediterranean Sea.     

The Use of Surrogate Data in Demographic Population Viability Analysis: A Case Study of California Sea Lions

Reliable data necessary to parameterize population models are seldom available for imperiled species. As an alternative, data from populations of the same species or from ecologically similar species have been used to construct models. In this study, we evaluated the use of demographic data collected at one California sea lion colony (Los Islotes) to predict the population dynamics of the same species from two other colonies (San Jorge and Granito) in the Gulf of California, Mexico, for which demographic data are lacking. To do so, we developed a stochastic demographic age-structured matrix model and conducted a population viability analysis for each colony. For the Los Islotes colony we used site-specific pup, juvenile, and adult survival probabilities, as well as birth rates for older females. For the other colonies, we used site-specific pup and juvenile survival probabilities, but used surrogate data from Los Islotes for adult survival probabilities and birth rates. We assessed these models by comparing simulated retrospective population trajectories to observed population trends based on count data. The projected population trajectories approximated the observed trends when surrogate data were used for one colony but failed to match for a second colony. Our results indicate that species-specific and even region-specific surrogate data may lead to erroneous conservation decisions. These results highlight the importance of using population-specific demographic data in assessing extinction risk. When vital rates are not available and immediate management actions must be taken, in particular for imperiled species, we recommend the use of surrogate data only when the populations appear to have similar population trends.     

The Larvae of Unarmed Nemerteans in Peter the Great Bay (Sea of Japan)

Nemertean pilidia belonging to the groups magnum, pyramidale, gyrans, recurvatum, and auriculatumwere found in Peter the Great Bay. Pilidium auriculatumis probably a little-known ribbon worm of the family Hubrechtiidae, which has never before been found in the Sea of Japan. Larvae of two species of the order Archinemertea were also found.     

New Data on the Distribution of Beaked Redfish Sebastes mentella (Sebastidae) in the Greenland Sea

Journal of Ichthyology - The ichthyological studies carried out at the shelf of North-Eastern Greenland in 2002–2017 new regions of dwelling of beaked redfish Sebastes mentella were...