Evidence of the impacts of emerging shark tourism in the Mediterranean (original) (raw)
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Loss of Large Predatory Sharks from the Mediterranean Sea
Conservation Biology, 2008
Evidence for severe declines in large predatory fishes is increasing around the world. Because of its long history of intense fishing, the Mediterranean Sea offers a unique perspective on fish population declines over historical timescales. We used a diverse set of records dating back to the early 19th and mid 20th century to reconstruct long-term population trends of large predatory sharks in the northwestern Mediterranean Sea. We compiled 9 time series of abundance indices from commercial and recreational fishery landings, scientific surveys, and sighting records. Generalized linear models were used to extract instantaneous rates of change from each data set, and a meta-analysis was conducted to compare population trends. Only 5 of the 20 species we considered had sufficient records for analysis. Hammerhead (Sphyrna spp.), blue (Prionace glauca), mackerel (Isurus oxyrinchus and Lamna nasus), and thresher sharks (Alopias vulpinus) declined between 96 and 99.99% relative to their former abundance. According to World Conservation Union (IUCN) criteria, these species would be considered critically endangered. So far, the lack of quantitative population assessments has impeded shark conservation in the Mediterranean Sea. Our study fills this critical information gap, suggesting that current levels of exploitation put large sharks at risk of extinction in the Mediterranean Sea. Possible ecosystem effects of these losses involve a disruption of top-down control and a release of midlevel consumers.
Sharks’ Status in the Mediterranean Sea Urgent Awareness is Needed
Sharks - Past, Present and Future [Working Title]
Cartilaginous fishes are a very ancient group; Sharks have lived on Earth for about 500 million years, since long before the dinosaurs. They have been able to survive and overcome five mass extinctions since their appearance. They play in fact a key role in maintaining the balance of marine ecosystems. More than 97% of the shark population has disappeared in the last two centuries. Currently, a high percentage is threatened, many are data-deficient. Many menaces face sharks, but fishing pressure seems to be most critical. This chapter focuses on the current status of cartilaginous fishes and progress on conservation measures and actions taken mainly through regional plans.
HUMAN IMPACT ON THE PRESENCE OF SHARKS AT DIVING SITES OF THE SOUTHERN RED SEA, EGYPT
Riassunto. Impatto della presenza umana sugli squali nei siti d'immersione del Mar Rosso meridionale, Egitto. Da giugno a novembre 2008 è stato condotto uno studio in merito all'impatto umano sulla presenza e sul comportamento degli squali nei seguenti siti d'immersione del Mar Rosso: Elphinstone Reef, Daedalus Reef, Big Brother Is., Small Brother Is., Zabargad Is., Rocky Is., and Habili Ali. È stato effettuato un totale di 194 ore di osservazione sul campo; gli squali sono stati incontrati durante 110 immersioni su 138. Sono state registrate 8 specie di squali per un totale di 292 esemplari: squalo balena Rhincodon typus (1 esemplare), pesce volpe pelagico Alopias pelagicus (12), squalo dalle pinne orlate di bianco Carcharhinus albimarginatus (1), squalo grigio di barriera Carcharhinus amblyrhynchos (61), squalo sericeo Carcharhinus falciformis (2), longimano Carcharhinus longimanus (123), squalo dalle pinne bianche di barriera Triaenodon obesus (5), pesce martello smerlato Sphyrna lewini (87). La frequenza di incontri a Elphinstone Reef è considerevolmente minore che nelle altre aree di studio. La presenza di subacquei ricreativi è stata registrata durante quasi tutte le immersioni: 134 casi su un totale di 138 immersioni, con una presenza in totale di 971 imbarcazioni e 15.601 subacquei. Sia il numero medio di subacquei che il numero medio di imbarcazioni registrate durante ogni immersione sono più elevati a Elphinstone Reef che nelle altre aree di studio. A Elphinstone Reef inoltre l'elevato numero di imbarcazioni è ampiamente distribuito sull'intera area, di conseguenza per gli squali è impossibile evitare la presenza umana. La massiccia presenza umana a Elphinstone Reef sta influenzando negativamente la presenza degli squali e potrebbe anche far aumentare le probabilità che si verifichino attacchi ad esseri umani. Il numero di imbarcazioni e di subacquei che frequentano quest'area e il loro comportamento devono essere regolati da un codice appropriato. È pertanto necessario che Elphinstone Reef sia urgentemente dichiarata area protetta.
Strengthening Angel Shark Conservation in the Northeastern Mediterranean Sea
Journal of Marine Science and Engineering
Angel sharks are among the most threatened species of sharks globally. Twenty-two species have been identified globally so far, with three species being present in the Mediterranean Sea: Squatina aculeata, Squatina oculata, and Squatina squatina. The Mediterranean populations of all three species have been assessed as Critically Endangered by the IUCN Red List of Threatened Species due to the steep decline of their populations as a result of their historical and current overexploitation by demersal fisheries. Therefore, currently there is an ongoing increasing effort for advancing the conservation of the species in the basin. Recently, in the context of the Regional Action Plan for Mediterranean Angel Sharks, the Aegean Sea and Crete have been identified as critical areas for all three species. This study provides the first predictive distribution map of the three angel shark species in the basin, while critical areas for the conservation of the species were identified through a sys...
Seasonal arrival and feeding of injured coastal sharks at fish farms in the Eastern Mediterranean
2018
Every summer coastal sharks (mostly sandbar sharks, Carcharhinus plumbeus) come to feed at open-sea fish farms near the Israeli coast, ever since their opening. Three of these sharks appear to suffer injuries of various degrees. At least one of the injured individuals, which suffers from a broken lower jaw, has been sighted at the fish farms every year since 2011. Providing a constant source of food to supplement feeding of wildlife has been shown to have both negative and positive impacts on wild populations and individuals. It may be possible that injured sharks, who have reduced abilities to find food in the wild, rely on such human related food sources to survive. Implications on the long-term effect of provisional feeding on sharks are discussed.
Aquatic Conservation-marine and Freshwater Ecosystems, 2021
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.