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Density Index (DI, N/km 2 ) of Dipturus oxyrinchus by overall deep interval (10-800 m) in the South of Sicily (GSA16) and Malta Island (GSA15) between 1994 and 2018 during MEDITSspring summer-(left) and between 1990 and 2006 during GRUND-autumn-(right).
Source publication
Batoid species play a key role in marine ecosystems but unfortunately they have globally declined over the last decades. Given the paucity of information, abundance data and the main life history traits for batoids, obtained through about three decades of bottom trawl surveys, are presented and discussed. The surveys were carried out in two areas o...
Contexts in source publication
Context 1
... speckled ray seemed to inhabit the shelf. In spring-summer, the species was most frequently encountered (1%) and most abundant (BI 0.6 ± 0.4 kg/km 2 ; DI 0.8 ± 0.5 N/km 2 ) on the slope in the Malta Island (Tables 1 and 2). In autumn, it was caught only in South of Sicily in 1995; therefore, a very low abundance indices were recorded (Table 3). ...
Context 2
... size of the cross is proportional to the number of positive hauls. The dashed areas represent depths below 800 m not explored in the present surveys., Figure S2: Overall positive hauls of Raja clavata in the GSA16 and GSA15. Blue and Red crosses indicate, respectively, GRUND (GRU) and MEDITS (MED). ...
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Internal tides are studied in the central Mediterranean Sea using observational data and numerical experiments. Both numerical results and observations indicate that the baroclinic variability in this area is dominated by the K1 diurnal tide. In agreement with previous studies, the diurnal internal tides have the characteristics of Kelvin-like bott...
Citations
... Although with the limitations mentioned above, the significant reduction of past frequent and very frequent species evidenced, is consistent with the findings of authors who focused on the population dynamics of elasmobranchs within the SoS (e.g., Garofalo et al., 2003;Geraci et al., 2021). Our long-term comparisons not only accord with the general decrease observed by these studies during the last 20 years but also highlight divergences from this general pattern in some species, such as for batoids R. clavata and R. miraletus and for sharks S. canicula and G. melastomus. ...
Chondrichthyans (sharks, rays, and chimaeras) are highly susceptible to the impacts of fisheries due to their vulnerable life-history traits. Over the last 100 years, several cases of local extinction have been documented in heavily fished areas across the Mediterranean Sea. In the Strait of Sicily (SoS), one of the main demersal fishing grounds of the Mediterranean, chondrichthyans constitute a significant component of both commercial and discarded bycatch. In this area, the lack of long-term data series on these species hinders our ability to fully comprehend the extent of changes due to both overfishing and climate variations. Here we aim to use historical data from the end of the 19th century, provided by Doderlein, to uncover evidence of long-term changes in the occurrence and diversity of these fishes. We employ a semi-quantitative approach to compare past data with recent frequency of occurrence estimates, to improve our ability to propose management advice. We report a decline in both the number of species and the frequency of occurrence of sharks and ray species in the study region over the past 150 years. Our findings shed light on the current status of sharks and rays compared to the historical data from the 19th century and highlight the urgent need to develop management strategies to mitigate the impact of harvesting on these vulnerable species.
... Despite the fact that there is no commercial interest in this species, much still needs to be learned about the distribution and biology of R. pallidus, specific to their biotopes [49]. Indeed, improving the knowledge about biological features as well as the spatial distribution of uncommon/threatened species requires closer collaborative efforts with fishermen [49][50][51][52][53][54][55][56]. Thus, we encourage data sharing between these stakeholders, which could be accomplished by holding special meetings, sharing pictures/descriptions, and retaining specimens that fishermen consider "uncommon". ...
The mantis shrimp Rissoides pallidus (Giesbrecht, 1910) is a rarely reported crustacean species in the Central Mediterranean Sea. In December 2020, during a trawl survey off Mazara del Vallo harbor (Strait of Sicily), two specimens of R. pallidus were captured on coastal detritus and coastal terrigenous mud bottoms at about 132 and 152 m depths. Additional information specific to biometrics, bottom types, depth preference, habitats, and geographic distribution of this crustacean species are provided.
... However, as suggested by Falsone et al. [53] and Sardo et al. [55], there is need for an adequate sampling methodology, which might help overcome such a challenge. Lastly, to improve the knowledge about the spatial distribution and biological features of uncommon or threatened species, an ad-hoc research project [56,57] and a closer collaboration with fishers [58][59][60] should be encouraged. ...
The mantis shrimp Rissoides pallidus (Giesbrecht, 1910) is among the rarely reported crustacean species in the Central Mediterranean Sea. In December 2020, during a trawl survey off Mazara del Vallo harbour (Strait of Sicily), two specimens of R. pallidus were captured on coastal detritus and coastal terrigenous mud bottoms at about 132 and 152 m depths. This current note, therefore, updates the existing knowledge of R. pallidus in the Strait of Sicily. Additional information specific to biometrics, bottom types, depth preference, habitats, and geographic distribution of this crusta-cean species are provided.
... Elasmobranch catches peaked in the early 2000 s before declining due to overfishing (Camhi et al., 1998;Walker, 1998;Ferretti et al., 2008Ferretti et al., , 2010Davidson et al., 2016). Although many other threats are involved in the decline of elasmobranch populations, including climate change, pollution, and habitat destruction (Seitz and Poulakis, 2006;Chin et al., 2010;Knip et al., 2010;Davidson et al., 2016;Dulvy et al., 2021), their greatest threat remains the fishing activity exerted by both directed and non-directed fisheries (Dapp et al., 2013;Geraci et al., 2021;Di Lorenzo et al., 2022;Falsone et al., 2022), which have devastated shark populations (MacNeil et al., 2020). Catch rates of threatened elasmobranch species are significant in many fisheries around the world (Fennessy, 1994;Francis et al., 2001;Stobutzki et al., 2002;Dulvy et al., 2014). ...
... However, the low intrinsic growth rate of elasmobranch species (Smith et al., 1998;Camhi et al., 1998;Musick et al., 2000), their late sexual maturity, and low fecundity, result in low resilience to fishing mortality (Hoenig and Gruber, 1990), making it difficult to rebuild stocks after overfishing (Stevens, 2000;Hutchings, 2012;Belhabib et al., 2017;Belhabiba et al., 2019;Johri et al., 2021;Geraci et al., 2021;Pacoureau et al., 2021;Falsone et al., 2022). By 2004, Mauritania had already seen a significant decrease in elasmobranchs catches as a result of the strong increase in fishing effort, and hence, management measures were put in place. ...
... As for concerns relating to the T90 50 mm, even though it was a very simple modification without any possible handling issues, some concerns were raised by the fishers owing to the important loss of marketable DPS. Therefore, in the future, it will be of vital importance to take into account the trade-off between the socio-economic and ecological points of view and to engage with as many fishers as possible in developing and optimising more selective gear (e.g., Geraci et al., 2019;Sardo et al., 2020b;Geraci et al., 2021b) to be translated into the decision-making process of the management regulations. ...
Introduction
Most Mediterranean fish stocks are overexploited owing to high fishing efforts and poor exploitation patterns. Demersal trawl fisheries are considered the most impactful fishery type because of the high quantities of unwanted catch that is then routinely discarded at sea.
Methods
In the present study, two types of by-catch reduction devices (BRDs), that is a sorting grid (Grid-T45 40 mm) and a T90 50 mm codend, were compared to a typical commercial bottom trawl net (control) in terms of size structures and catch per unit effort to assess the effect of gear modification on the selectivity of crustacean fisheries in the central Mediterranean Sea. In particular, three randomly selected trawlers were involved in a paired hauls experiment fishing at the same time in the same fishing ground. Each trawler carried out four hauls per day during a 3-day campaign for a total of 36 hauls. The target species of the fishery is Parapenaeus longirostris (herein DPS), and the main commercial by-catch is Merluccius merluccius (herein HKE).
Results
The results showed that the landing per unit effort (LPUE) of DPS was higher for Grid-T45 40 mm net, although it did not differ significantly from that of the control net. Conversely, the discard per unit effort (DPUE) of the control net was significantly higher than of both BRD configurations. For HKE, a slightly higher LPUE was recorded using the T90 50 mm codend compared to that of the control, but this result was not statistically significant. The lowest DPUE was found for the T90 50 mm codend, with significant differences compared to that of the control and Grid-T45 40 mm net. The catch comparison of the size structures analysed through generalised linear mixed models highlighted that the Grid-T45 40 mm net was more effective in catching adult DPS, whereas the T90 50 mm codend was more selective for adult HKE.
Discussion
In conclusion, although further studies should be carried out in future to test the performance of the BRDs in different areas and seasons, the investigated gear seems to be promising for reducing the catch of undersized individuals and contributing to mitigating the current overfishing of DPS and HKE.
... Fishing activity is one of the most important anthropogenic impacts affecting marine resources and consequently the ecological equilibria in marine ecosystems [1][2][3][4]. Among the different fisheries, bottom trawling is considered one of the most impactful techniques in the Mediterranean due to high quantities of unwanted catch, including the incidental catch of non-target species and juveniles of both target and non-target species, which are either discarded because of their low economic value or because of legal restrictions, e.g., [5][6][7]. Excluding temporal and spatial closures, the most common way of addressing the issue of by-catch in towed gear has been to improve gear selectivity. Indeed, to mitigate the problem, the European Union established conservation measures such as minimum legal mesh size and the Minimum Conservation Reference Size (MCRS), under Reg. ...
Stock assessments routinely evaluate the status of commercially harvested species, but seldom account for the possible mortality of released or escaping fish. This study presents a method for estimating the escape survival of the red mullet (Mullus barbatus) from demersal trawling in the Central Mediterranean Sea. Fish escaping from the trawl codend were collected in a detachable cage, which was lined to reduce water flow and protect the sampled fish from further fatigue and injury. Control fish (from an open codend) showed high survival, 94% (87–97%, 95% Confidence Interval), and minimal injuries, while fish escaping through codend meshes had significantly increased injuries and reduced survival, 63% (55–70%). During 7 days of captive monitoring, treatment group mortality was highest in the first 24 h and ceased for both groups within 48 h. Conflicting length-related mortality was observed, where larger treatment fish had a higher probability of dying, while the opposite was observed in the controls. Analysis showed that treatment fish were significantly more injured than control fish, with treatment fish predominantly injured in the head zone. In conclusion, this improved methodology should be repeated to provide accurate escape mortality estimates for the improved stock assessment of the red mullet in the Central Mediterranean.
... The bycatch and discards of elasmobranchs would, therefore, be considered high (33.2%) for trawl fisheries (Coelho and Erzini, 2008;FAO, 2020;Geraci et al., 2021b;Falsone et al., 2022). Nevertheless, artisanal fishery such as trammel net (37.8%) and longline (7.7%) also provide a significant bycatch of elasmobranch species (Erzini et al., 2002;Baeta et al., 2010;Catanese et al., 2018;FAO, 2020). ...
Discards remain among the main negative impacts of fishing activities, and their reductions are strengthened by the European Common Fisheries Policy (European Regulation 1380/2013). Trammel net fisheries appear more sustainable compared with other fishing techniques, especially from an ecological viewpoint. Despite this, reports show that trammel net fisheries deliver discard quantities between 10% and 43% of the total catch biomass. To supplement existing information, this current work attempts to address the discard reduction using guarding net in the small-scale fisheries of Egadi Islands MPA (Western Sicily, Central Mediterranean Sea). To assess the reduction of unwanted catches, 48 experimental fishing trials were conducted within a 6-month period. The experimental fishing trial employed a trammel net made up of 20 panels alternated with two different net configurations. The control panels (CN) held a large outer (180 mm) and small inner (31.25 mm) meshes. The test panels (GN) with guarding net constituted a three-mesh-high (50-mm mesh size) net placed between trammel net panels and a lead line. A total of 3,310 individuals belonging to 106 taxa and nine phyla were caught. Crustaceans were the most abundant unwanted catches in the control panels, whereas bioconstructions occurred in the guarding net panels. The discard ratios of CN and GN panels were statistically different (t-value = –2.55; p< 0.05). The analysis of catch per unit effort showed higher catches of CN panels for both commercial and discard fractions (p< 0.05). Moreover, the guarding net panels caught the main discarded species at 20% lower compared with the control. The overall value of the catch at the CN panels (€ 3,366.90) was higher than the total income (€ 2,043.70) generated using the GN panels, which suggests a significant commercial loss of 40% (p< 0.05).
... Currently, shark attacks incidents do not exist in Greece, but this was not true during the studied period. It is well known that the Mediterranean Sea is a hotspot for shark extinction globally [26,27], primarily as a result of overfishing [15,24], but also due to habitat degradation [15]. Although [28] underlines a direct link between shark attacks and the increasing density of sea-users, we must further consider the possibility that some shark species have shifted their distribution as a result of the increasing human pressure on the coastal ecosystems and urbanization (increase in population in the two biggest cities in Greece by more than 130% between 1951-2021: [29]). ...
The lack of historical data on shark presence, distribution, and status in the Eastern
Mediterranean undermines efforts to manage and protect their populations. An exhaustive review of anecdotal references related to shark presence during the early and development phase of Greek fisheries (1883–1983) was conducted. In the early-20th century (1912), the first sighting of the presence of a dead shark was reported in the Ionian Sea. Later on, the presence of sharks gradually increased up to 1969, with most records being more frequent for the Aegean Sea, whereas the number of sharks being sighted declined leading up to the middle of 1980s. The increase in shark attacks during the mid-20th century led to a calling for culling of sharks in co-operation with the competent authorities promoting the permission to hunt sharks with firearms and offering rewards for killed individuals. A high number of these observations potentially resulted from shark attacks on people, whereas this is
not currently evident. This is an indicator of the lower abundance of sharks in modern times and subsequently an alteration in the way that our current modern society is approaching the protection of such vulnerable species.
... Raja asterias appears to be also among the skates most affected by the bycatch of trawlers and small-scale fishery (Biton-Porsmoguer & LLoret, 2020;Ricci et al., 2021). The International Union for Conservation of Nature classifies this as a "near threatened" species (Serena et al., 2015) due to the increasing fishing pressure and evidence that its population seems to be in an ongoing depletion in some Mediterranean areas, like the Adriatic Sea and the Strait of Sicily Geraci et al., 2021), contrary to the expected outbreak of mesopredators. The Adriatic Sea (General Fisheries Commission for the Mediterranean Sea-Geographical Sub-area 17, GSA 17 from here on) is the most heavily exploited basin in the EU waters, with the lowest seabed integrity due to bottom trawling activity (Eigaard et al., 2017). ...
The Mediterranean Sea is among the three biodiversity hotspots of the world where elasmobranchs are severely threatened. Elasmobranchs act as apex or meso-predators within marine food webs and the loss/decline of apex predators determines the mesopredator release, leading in turn to increased predation on smaller prey. However, also several mesopredators (including rays, skates and small sharks) are intensively fished, being of commercial interest, or by-caught, and thus mesopredators increase could not be so evident. We analysed the trophic ecology of an endemic Mediterranean ray, the starry ray Raja asterias, at a seasonal scale from the Adriatic basin, one of the most intensively exploited area of the Mediterranean, by means of stomach contents and stable isotopes analyses. Our results evidenced that starry rays rely on benthic sources including species of local commercial values, such as swimming crabs, small cephalopods, and stomatopods and share the same trophic position with other elasmobranchs (rays, skates, and small sharks) and other mesopredators (e.g., common soles, Norway lobsters and mullets). As all mesopredators are overexploited, as well as their benthic prey are affected by intense trawl-fishing, the whole food webs are disrupted and neither the classical trophic cascade nor the mesopredator release hypothesis could be verified. Conservation measures for these species, such as the release after capture or the application of exclusion grids to the net, should be applied in areas where populations are strongly impacted by trawling.
... In particular, the trawling fleet exploits the deeper fishing ground, targeting deep-water crustaceans such as Aristaeomorpha foliacea, Aristaeus antennatus, and Nephrops norvegicus [59,60], as well as the shallow fishing ground, targeting mainly M. barbatus, M. surmuletus, sparids and cephalopods [43,61]. Among these fishing typologies, an important component of commercial and discarded bycatch comprises cartilaginous fishes [62]. This area represents one of the most important fishing grounds for demersal species, exploited mainly by trawl fisheries [55]. ...
... In particular, the trawling fleet exploits the deeper fishing ground, targeting deep-water crustaceans such as Aristaeomorpha foliacea, Aristaeus antennatus, and Nephrops norvegicus [59,60], as well as the shallow fishing ground, targeting mainly M. barbatus, M. surmuletus, sparids and cephalopods [43,61]. Among these fishing typologies, an important component of commercial and discarded bycatch comprises cartilaginous fishes [62]. ...
... Considering the current change in the fishing pattern in the Strait of Sicily, attention should be paid to limiting the impact of deep-water red shrimp fisheries on sensitive species such as Elasmobranchii living on slope fishing grounds off the southern coast. Together with more effective control of fishing efforts, management measures aimed at increasing the selectivity of trawling gear, by either implementing an ad hoc modified sorting grid [62,84], raising the footrope [85], or cutting the rigging twine [39]; increasing the number of cartilaginous fish returned to the sea alive through education on proper handling [86][87][88][89], and protecting areas and periods where spawning and juveniles aggregate would contribute to improving the state of Elasmobranchii populations that suffer the impact of fisheries [90,91]. ...
Elasmobranchii (sharks and rays), which have peculiar and vulnerable life-history traits, are highly threatened by fishing activities. Indeed, between 53% and 71% of Mediterranean elasmobranch species are at risk of extinction. In this context, using the abundance MSY (AMSY) model, the present study provides an assessment of 20 batoids and 16 shark species in the Strait of Sicily, sampled during a bottom trawl survey from 1995 to 2020. Overall, the outputs underline a progressively improving condition for shark and ray assemblages of both shelf and eurybathic zones. As for slope-dwelling
species, a horseshoe-shaped dynamic, characterized by a progressive decrease in relative harvesting
pressure and an increase in relative biomass followed by an increase in fishing pressure and decrease in biomass, was detected. The dynamics of the Elasmobranchii living in the Strait of Sicily appear to be affected by changes in the fishing patterns of trawlers, showing a shift from shallow water to bathyal fishing grounds and targeting deep-water red shrimp. In this context, it seems wise to limit the impact of deep-water fisheries on Elasmobranchii by reducing fishing efforts and implementing ad hoc management measures aimed at safeguarding these vulnerable species.
