Influence of seasonality on cetacean diversity,abundance, distribution and habitat use in the western Mediterranean Sea: Implications for conservation

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An integrated approach for cetacean knowledge and conservation in the central Mediterranean Sea using research and social media data sources

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Characterizing the potential habitat of European anchovy Engraulis encrasicolus in the Mediterranean Sea,at different life stages

Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different life stages in relation to environmental conditions is an interesting subject from both ecological and management points of view. For this purpose, acoustic data from different seasons and different parts of the Mediterranean Sea along with satellite environmental and bathymetry data were modelled using generalized additive models. Similarly, egg distribution data from summer ichthyoplankton surveys were used to model potential spawning habitat. Selected models were used to produce maps presenting the probability of anchovy presence (adults, juveniles and eggs) in the entire Mediterranean basin, as a measure of habitat adequacy. Bottom depth and sea surface chlorophyll concentration were the variables found important in all models. Potential anchovy habitats were located over the continental shelf for all life stages examined. An expansion of the potential habitat from the peak spawning (early summer) to the late spawning season (early autumn) was observed. However, the most suitable areas for the presence of anchovy spawners seem to maintain the same size between seasons. Potential juvenile habitats were associated with highly productive inshore waters, being less extended and closer to coast during winter than late autumn. Potential spawning habitat in June and July based on ichthyoplankton surveys overlapped but were wider in extent compared with adult potential habitat from acoustics in the same season. Similarities and dissimilarities between the anchovy habitats as well as comparisons with sardine habitats in the oligotrophic Mediterranean Sea and other ecosystems with higher productivity are discussed.     

Population genetic structure of common bottlenose dolphins (Tursiops truncatus) in the Adriatic Sea and contiguous regions: implications for international conservation

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Changes in threats to macroalgal forests (Cystoseira sensu lato) at three restoration sites in the Mediterranean Sea

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Perish legally and ecologically: the ineffectiveness of the minimum landing sizes in the Mediterranean Sea

Abstract  Minimum landing size (MLS) is one technical measure used to manage fisheries with the aim of allowing enough juveniles to survive and spawn. In this study the practical and ecological efficiency of the MLSs set by European Union (Regulation 1967/2006) and Greek legislation for 13 fish species caught with five gears in the Ionian Sea was tested using length measurements from 22 382 individuals. The percentage of individuals with lengths smaller than MLS was estimated. In addition, MLSs were compared against length at 50% maturity ( L ₅₀) and the percentages of individuals caught per species and gear with lengths smaller than the L ₅₀ were also estimated. The mean percentage of individuals caught with lengths smaller than MLS ranged from 5.9% for longliners to 42.6% for beach-seiners, showing the practical inefficiency of this measure. In addition, all MLS were smaller than the corresponding L ₅₀ and L ₅₀ − SE values and across species the mean percentage of the immature individuals caught was very high, ranging from 55% for longliners to 92% for beach-seiners, indicating that the vast majority of the individuals caught did not have the chance to spawn even once. Thus, the existing MLSs are ecologically inefficient for sustainable management.     

Abundance,activity and critical habitat of the striped dolphin Stenella coeruleoalba in the Gulf of Taranto (northern Ionian Sea,central Mediterranean Sea)

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Benthic habitat modelling and mapping as a conservation tool for marine protected areas: A seamount in the western Mediterranean

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Cold‐water coral Madrepora oculata in the eastern Ligurian Sea (NW Mediterranean): Historical and recent findings

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A new synthetic index and a protocol for monitoring the status of Posidonia oceanica meadows: a case study at Sanremo (Ligurian Sea,NW Mediterranean)

• 1. The status of a Posidonia oceanica meadow in front of the town of Sanremo, Italy, was studied through a combined use of benthic mapping and synthetic indices.
• 2. Mapping was accomplished by integrating side scan sonar imagery and data collected by scuba diving along transects placed perpendicularly to the coastline. A thematic map (scale 1:5000) was produced. Extent of the meadow, occurrence of dead matte areas, and morphology of the lower limit (with new definition) are all described.
• 3. Two synthetic environmental indices were applied to transect data in order to quantify the status of the meadow: the Conservation Index and the Substitution Index. The former is related to the proportion of dead matte; the latter is a novel index measuring the amount of replacement of the ‘constructional’ seagrass P. oceanica by the ‘non‐constructional’ seagrass Cymodocea nodosa. The potential of a ‘phase shift’ in Ligurian Sea seagrass meadows is discussed.
• 4. The approach here proposed, based on detailed mapping plus synthetic indices, may provide immediate information to evaluate the state of Mediterranean Posidonia oceanica for monitoring and management.

Copyright © 2006 John Wiley & Sons, Ltd.     

`Ocean triads' in the Mediterranean Sea: physical mechanisms potentially structuring reproductive habitat suitability (with example application to European anchovy, Engraulis encrasicolus)

Summaries of maritime weather reports and mean seasonal satellite-sensed ocean colour distributions for the Mediterranean Sea are used to identify characteristic configurations of physical mechanisms promoting (i) nutrient enrichment, (ii) concentration of larval food distributions, and (iii) local retention of eggs and larvae. Five subbasin scale `ocean triads', hypothesized to be particularly favourable groupings, are identified in the Aegean Sea, the Gulf of Lions and nearby Catalan Coast, the Alboran Sea, the Straits of Sicily/Tunisian Coast, and the Adriatic Sea. These are examined in relation to available knowledge of anchovy spawning grounds. All areas are characterized by patterns of linked wind-driven Ekman upwelling and downwelling. All areas except the Straits of Sicily are found to have inputs of less saline surface waters offering raised nutrient concentrations, enhanced upper layer stability, and frontal density contrasts, and to have areas where the characteristic rate of turbulent mixing energy input by the wind fall below a reference intensity level. All areas, except the Sicilian Channel/Tunisian Coast, also contain abundant locally reproducing anchovy populations.     

Dolphins in a bottle: abundance,residency patterns and conservation of bottlenose dolphins Tursiops truncatus in the semi‐closed eutrophic Amvrakikos Gulf,Greece

• 1. Boat surveys were conducted between 2002 and 2005 to study bottlenose dolphins living in the 400 km² Amvrakikos Gulf, western Greece. During 116 survey days, 4705 km of total effort resulted in the individual photo‐identification of 106 animals, through long‐term natural markings on their dorsal fins.
• 2. Mark–recapture analyses based on the M_th model provided estimates of 82 marked individuals in 2003 (95% CI=80–91), 92 in 2004 (95% CI=86–108) and 98 in 2005 (95% CI=94–110). To include the unmarked portion of the population, the proportion of unmarked individuals was computed based on the number of photographs of marked and unmarked dorsal fins. The mean proportion of unmarked animals in the population was 0.338 (95% CI=0.288–0.389). By adding this to the estimate for marked animals in 2005, considered as the most robust, a total population estimate of 148 individuals (95% CI=132–180) was obtained.
• 3. Dolphin encounter rates in 2003–2005 did not show significant variations, and averaged 7.2 groups per 100 km or 72.5 individuals per 100 km. Encounter rates within the Gulf were about one order of magnitude greater than those found for bottlenose dolphins in nearby eastern Ionian Sea coastal waters.
• 4. Mean dolphin density in the Gulf was 0.37 animals km^?2. This relatively high density, together with high levels of site fidelity shown by most individuals, was thought to be related primarily to prey availability, particularly of epipelagic schooling fish.
• 5. The importance of the semi‐closed Amvrakikos Gulf for bottlenose dolphins and other threatened species encourages the adoption of measures aimed to conserve its valuable ecosystems and raise the naturalistic profile of the area, while promoting environment‐conscious development. Meaningful action includes restoring natural hydrology (e.g. freshwater input from rivers), curtailing pollution from various sources, responsible fisheries and aquaculture management, and control of illegal fishing. Interactions between dolphins and fisheries also deserve careful quantitative investigation.

Copyright © 2007 John Wiley & Sons, Ltd.     

Modeling environmental,temporal and spatial effects on twaite shad (Alosa fallax) by‐catches in the central Mediterranean Sea

Modeling the relationships between environmental factors and the distribution at sea of species of conservation interest can be useful in predicting their occurrence from a local to a regional scale. This information is essential for planning management and conservation initiatives. In this study, generalized additive models (GAMs) were applied to investigate the influence of environmental, temporal and spatial variables on the catch rates of the twaite shad Alosa fallax (Lacepède) by the pelagic trawl fishery in the north‐central Adriatic Sea. Presence/absence and abundance [catch per unit effort (CPUE)] data between 2006 and 2012 were separately modeled, and the two models were then validated using a test data set. The most important factor influencing the presence and abundance of adult twaite shads was the spatial predictor (latitude × longitude). Two areas of major shads aggregations were observed, the most important of which being located near the estuaries of three main river systems of northern Italy. The twaite shad presence was also significantly affected by season, the largest and lowest occurrences being observed in autumn and spring, respectively. Among the environmental variables tested, only sea surface temperature was included in both models. Alosa fallax showed a wide thermal tolerance (6–27°C) with preference for temperature around 23°C. The model developed from the abundance data showed a moderate predictive power, whereas the accuracy of the presence/absence model was rather low. Some conclusions on the ecological requirements of A. fallax at sea arising from this study are useful to orient future monitoring and research programs and to develop effective conservation actions.     

A geostatistical approach for the stock assessment of the edible sea urchin, Paracentrotus lividus, in four coastal zones of Southern and West Sardinia (SW Italy, Mediterranean Sea)

Quantitative surveys of the edible sea urchin, Paracentrotus lividus, were conducted in four fishing zones of Sardinia (Southern Italy, Mediterranean Sea), in Autumn 2007. A total of 120 stations were geo-located along a bathymetric gradient ranging from 0 to 10 m. A geostatistical method was used to evaluate spatial patterns in density and to estimate harvestable stocks. Variographic analyses showed that the isotropic Gaussian and spherical models successfully explained the spatial structure of sea urchin assemblages in these areas. Density maps obtained by punctual kriging showed that sea urchin populations tend to be patchy rather than uniform in their density distribution. A combination of mapping and size categories was used to generate diverse scenarios of harvestable stocks (specimens ≥50 mm in diameter) before the start of the current fishing season. We conclude that the geostatistical approach, which takes into consideration the spatial autocorrelation structure of the populations in small areas, seems to be a good estimator of P. lividus density and biomass and for the assessment of its harvestable stocks, and thus provides an initial step towards a scientific approach to the management of local sea urchin fisheries.     

A tale of two seas: a meta‐analysis of crustacean stocks in the NE Atlantic and the Mediterranean Sea

Meta‐analysis of marine biological resources can elucidate general trends and patterns to inform scientists and improve management. Crustacean stocks are indispensable for European and global fisheries; however, studies of their aggregate development have been rare and confined to smaller spatial and temporal scales compared to fish stocks. Here, we study the aggregate development of 63 NE Atlantic and Mediterranean crustacean stocks of six species (Nephrops norvegicus, Pandalus borealis, Parapenaeus longirostris, Aristeus antennatus, Aristaeomorpha foliacea and Squilla mantis) in 1990–2013 using biomass index data from official stock assessments. We implemented a dynamic factor analysis (DFA) to identify common underlying trends in biomass indices and investigate the correlation with the North Atlantic Oscillation (NAO) index. The analysis revealed increasing and decreasing trends in the northern and southern NE Atlantic, respectively, and stable or slowly increasing trends in the Mediterranean, which were not related to NAO. A separate meta‐analysis of the fishing mortality (F) and biomass (B) of 39 analytically assessed crustacean stocks was also carried out to explore their development relative to MSY. NE Atlantic crustacean stocks have been exploited on average close to F_MSY and remained well above B_MSY in 1995–2013, while Mediterranean stocks have been exploited 2–4 times above F_MSY in 2002–2012. Aggregate trends of European crustacean stocks are somewhat opposite to trends of fish stocks, suggesting possible cascading effects. This study highlights the two‐speed fisheries management performance in the northern and southern European seas, despite most stocks being managed in the context of the European Union's Common Fisheries Policy.     

A shot in the dark for conservation: Evidence of illegal commerce in endemic and threatened species of elasmobranch at a public fish market in southern Brazil

1. The illegal sale of endangered elasmobranchs has been recorded in a number of different Brazilian states, where sharks and rays are being marketed primarily as ‘cação’ or ‘viola’. Brazil is ranked among the top 10 nations worldwide that harvest most sharks, causing an immeasurable impact on the local elasmobranch populations.
2. The present study applied the DNA barcoding technique, based on the cytochrome C oxidase subunit I gene, for the molecular identification of the elasmobranch species sold as processed products under the generic names of ‘cação’, ‘mangona’, ‘azul’, ‘cambeva’, ‘fiuso’ and ‘lombo preto’, in the fish market of the city of Florianópolis, capital of the state of Santa Catarina, Brazil.
3. Nine elasmobranch species were identified in the 56 samples analysed, including six sharks and three rays, representing six families, the Carcharhinidae, Sphyrnidae, Squatinidae, Arhynchobatidae, Myliobatidae and Gymnuridae. Prionace glauca, identified in more than half (56%) of the samples analysed, is listed as Near Threatened by the International Union for the Conservation of Nature.
4. Six species identified in the present study, Sphyrna zygaena, Sphyrna lewini, Squatina guggenheim, Carcharhinus signatus, Gymnura altavela and Rioraja agassizii, are under some level of risk of extinction, while two others (Rhizoprionodon lalandii and Myliobatis goodei) are listed as Data Deficient.
5. Our results indicate that the commercial exploitation of endemic sharks and rays at risk of extinction is commonplace in southern Brazil. This reinforces the need for more systematic monitoring of the trade in fishery products and more effective application of the environmental legislation and conservation programmes.

     

A closer look at the bycatch of medium-sized and large sharks in the northern Catalan coast (north-western Mediterranean Sea): Evidence of an ongoing decline?

1. Historically, the Mediterranean Sea supported a rich shark fauna. Presently, however, populations of most shark species have significantly declined, largely due to intense fishing pressure.
2. Interviews with crew members of bottom trawlers, drifting longliners and bottom longliners operating off the Costa Brava (Catalonia, NE Spain) were conducted between October 2016 and July 2017 in order to gather information on the current bycatch rate of several shark species.
3. Interviews covered 41.2% of the fleet and respondents were asked for the bycatch of selected shark species—Alopias vulpinus, Cetorhinus maximus, Galeorhinus galeus, Hexanchus griseus, Isurus oxyrinchus, Mustelus spp., Prionace glauca, and Squalus acanthias—in two distinct time periods.
4. Bottom trawlers captured the highest diversity of species (eight) followed by bottom longliners (seven), and drifting longliners (three). Most respondents (89.7%) declared having captured at least one shark from 2006 to 2016 but only 56.4% declared having captured at least one shark from 2016 to 2017.
5. From 2016 to 2017, the whole fleet captured 89 specimens of H. griseus (95% confidence interval (CI) = 145, 34), 14 of G. galeus (95% CI = 30, 0), 3 of A. vulpinus (95% CI = 8, 0), 3 of I. oxyrinchus (95% CI = 8, 0), 3 of C. maximus (95% CI = 6, 0), and no Mustelus spp. The total bycatch of P. glauca and S. acanthias was uncertain due to extremely loose confidence intervals.
6. A significant decline was perceived by fishermen in the bycatch of C. maximus and S. acanthias, whereas the bycatch of H. griseus was considered to have remained stable.
7. This study suggests a dramatic reduction in the abundance of most of the medium-sized and large sharks of the Costa Brava and the likely disappearance of Mustelus spp. from the area. Only H. griseus, S. acanthias, and P. glauca are still being bycaught frequently.