I dati disponibili rivelano che ľattuale fauna di squali delle acque turche comprende 37 specie confermate: Hexanchus griseus, Heptranchias perlo, Echinorhinus brucus, Squalus acanthias, S. ...blainvillei, Centrophorus cf. uyato, Etmopterus spinax, Somniosus rostratus, Oxynotus centrina, Dalatias licha, Squatina aculeata, S. oculata, S. squatina, Carcharias taurus, Odontaspis ferox, Alopias superciliosus, A. vulpinus, Cetorhinus maximus, Carcharodon carcharias, Isurus oxyrinchus, Lamna nasus, Galeus melastomus, Scyliorhinus canicula, S. stellaris, Galeorhinus galeus, Mustelus asterias, M. mustelus, M. punctulatus, Carcharhinus altimus, C. brachyurus, C. brevipinna, C. falciformis, C. limbatus, C. obscurus, C. plumbeus, Prionace glauca, e Sphyrna zygaena. Sulla base delle informazioni attuali, la minaccia piu significativa per gli squali nelle acque turche e l'impatto negativo della cattura accidentale.
Sharks (765 specimens from ten species) from the Mediterranean Sea off Algiers, Algeria, were examined for the presence of gill monogeneans. The following deep-sea sharks were investigated from 2009 ...to 2015:
(27 specimens);
(39);
(67);
(19);
(189);
(261),
3), and
(100). In addition, two pelagic shark species were examined:
(7), and
(53). Only two species of gill monogeneans were found.
(Cerfontaine, 1899) Euzet et Maillard, 1974 was found on its type-host
comparative measurements are provided, and Algeria is a new geographic record.
n. sp. from
is described here. We found that the species of
Cerfontaine, 1899 can be separated into two groups, according to body size. Small-bodied species include 7 species. Large-bodied species (body > 20mm) include
(Van Beneden, 1853),
Yamaguti, 1958 and
n. sp; the latter is distinguished from the two other species by a characteristically slender body. A sequence of Cytochrome Oxidase Type I (COI) gene, potentially useful for barcoding, was obtained for
n. sp. and is the first for the family Hexabothriidae.
The bluntnose sixgill shark, Hexanchus griseus, is a widely distributed but poorly understood large, apex predator. Anecdotal reports of diver-shark encounters in the late 1990's and early 2000's in ...the Pacific Northwest stimulated interest in the normally deep-dwelling shark and its presence in the shallow waters of Puget Sound. Analysis of underwater video documenting sharks at the Seattle Aquarium's sixgill research site in Elliott Bay and mark-resight techniques were used to answer research questions about abundance and seasonality. Seasonal changes in relative abundance in Puget Sound from 2003-2005 are reported here. At the Seattle Aquarium study site, 45 sixgills were tagged with modified Floy visual marker tags, along with an estimated 197 observations of untagged sharks plus 31 returning tagged sharks, for a total of 273 sixgill observations recorded. A mark-resight statistical model based on analysis of underwater video estimated a range of abundance from a high of 98 sharks seen in July of 2004 to a low of 32 sharks seen in March of 2004. Both analyses found sixgills significantly more abundant in the summer months at the Seattle Aquarium's research station.
This paper confirms the new distributional records of four rare deep-water chondrichthyans viz. sharpnose sevengill shark, Heptranchias perlo (Bonnaterre, 1788); bluntnose sixgill shark, Hexanchus ...griseus (Bonnaterre, 1788); bramble shark, Echinorhinus brucus (Bonnaterre, 1788); and sicklefin chimaera, Neoharriotta pinnata (Schnakenbeck, 1931) from the Andaman waters in the Indian EEZ. The above-mentioned four fish species have not been reported earlier from this region. More exploratory surveys in the region are essential to understand the diversity and distribution pattern which is essential for critical management actions. An updated checklist of chondrichthyans known from Andaman and Nicobar waters of India is also presented.
We report the first record and morphometry of a complete juvenile Hexanchus griseus female shark, caught in Punta Lobos, Baja California Sur, Mexico. The oceanographic conditions of the area, where ...the specimen was caught, coincide with the habitat previously described for this shark species, with low temperature, stable salinity and high hydrostatic pressure. There is an overall lack of information about H. griseus in Mexico, with only eight records of its presence in the Mexican Pacific. Moreover, none of these previous records provided detailed information on the morphometry of a whole bluntnose sixgill shark. Here, we present the morphometric measures of a complete individual caught in shallow waters. We expect this information to be useful for future comparisons of specimens caught in other coastal regions.
The Bluntnose Sixgill Shark, Hexanchus griseus, is a large predatory shark, has a worldwide distribution and is listed as near-threatened by the International Union of Conservation of Nature (IUCN). ...The Seattle Aquarium collected observations of free-swimming Sixgill Sharks in Elliott Bay, Washington, under the aquarium’s pier in 20 m of water from 2003 to 2005 and again from 2008 to 2015 using the same methodology. Compared to total Sixgill sightings between 2003-2005 (273) fewer total Sixgills were sighted at the aquarium’s research station between 2008-2015 (33). The reason for the observed decline in sightings in unknown but based on data from other studies on Sixgills in Puget Sound during the same timeperiod the authors hypothesize the decrease may be due to natural variability of juvenile Sixgill recruitment to Elliott Bay.
Analysis of 81 Hexanchus griseus related articles published in major Turkish newspapers and internet media between 1974 and 2009 revealed that the tenor of the coverage was neutral in 40 (49.3%) ...articles, 37 (45.6%) were negative and only 4 (4.9%) were positive. A utilitarian perspective prevailed, appearing in 51 (62.9%) of the articles examined. Since 2004, the diversification of media opportunities has caused an increase in the number of published articles on H. griseus. In Turkey, people share the preconceived notion of sharks that has been deeply embedded into their psychology by years of irresponsible media reporting. Articles depicting the sixgill shark as a possible source of profit can motivate the fishermen to catch this vulnerable species and cause an artificial fishing pressure on H. griseus.Original Abstract: L'autore presenta l'analisi di 81 articoli correlati a Hexanchus griseus, pubblicati dai piu importanti giornali della Turchia e sul Web nel periodo 1974-2009. I risultati dell'analisi evidenziano che il tono di copertura era neutrale in 40 articoli (ossia nel 49,3% dei casi), negativo in 37 articoli (45,6% dei casi) e positivo in soli 4 articoli (4,9% dei casi). In 51 articoli esaminati (62,9% dei casi) prevaleva una prospettiva utilitaria. La diversificazione delle oppurtunita offerte dai mass media ha causato un aumento del numero di articoli pubblicati su H. griseus a partire dal 2004. In Turchia la popolazione condivide i pregiudizi sugli squali, che sono stati profondamente radicati nella loro psicologia da anni di servizi giornalistici irresponsabili. Gli articoli che descrivono lo squalo capopiatto quale possibile fonte di guadagno possono motivare i pescatori a catturare questa specie vulnerabile e causare una pressione artificiale di pesca su H.griseus. Analiza 81 clankov o vrsti Hexanchus griseus, objavljenih v vecjih turskih casopisnih in internetnih medijih v letih 1974-2009, pri 40 clankih (49,3%) ugotavlja nevtralno porocanje, pri 37 (45,6%) negativno in samo pri 4 (4,9%) pozitivno. Prevladuje utilitarna perspektiva, ki jo lahko opazimo pri 51 (62,9%) obravnavanih prispevkih. Od leta 2004 se je zaradi diverzifikacije moznosti medijskega porocanja povecalo stevilo objavljenih clankov o H. griseus. V Turciji imajo ljudje vnaprej izoblikovano predstavo o morskih psih, ki se je v letih neodgovornega medijskega porocanja trdno zasidrala v njihovi zavesti. Clanki, ki morskega psa sesteroskrgarja prikazujejo kot mozen vir zasluzka, lahko ribice vzpodbudijo k lovu na to obcutljivo vrsto in povzrocijo umeten ribolovni pritisk na H. griseus.
One hundred and fifty specimens of Hexanchus griseus (Bonnaterre, 1788) were caught by commercial fishing vessels in the seas of Turkey, between 16 July 1967 and 4 February 2013. Regarding the number ...of captured specimens per marine areas, the highest number of captures was recorded in the Sea of Marmara (90 specimens; 60 %), followed by the Aegean (41 specimens; 27.3 %), Mediterranean (15 specimens; 10 %) and Black (3 specimens; 2 %) seas. A single stranded individual was also recorded in the Canakkale Strait. Regarding the number of recorded specimens it is obvious that the Sixgill Shark Data Bank of Turkey holds a significant number of H. griseus specimens caught in the eastern Mediterranean Sea, both reported in historical and contemporary studies. The sex ratio of the examined specimens of H. griseus is 1:2.61 in favour of females. Analysis of the fishing gear used for 72 of 150 examined sixgill sharks indicates that the most common fishing gear used to catch H. griseus is purse-seine, followed by several types of bottom fishing gear. Total length of the recorded specimens ranged between 50 and > 650 cm TL for both sexes; however, catches were dominated by two size groups, 250-350 cm and 350-450 cm TL, respectively.Original Abstract: Centocinquanta esemplari di Hexanchus griseus (Bonnaterre, 1788) sono stati catturati da pescherecci commerciali nei mari della Turchia fra il 16 luglio 1967 ed il 4 febbraio 2013. Il numero piu alto di catture e stato registrato nel mar di Marmara (90 esemplari; 60 %), seguito dall'Egeo (41 esemplari; 27,3 %), dal Mediterraneo (15 esemplari; 10 %) e dal mar Nero (3 esemplari; 2 %). Un individuo arenato e stato inoltre rinvenuto nello stretto dei Dardanelli. Visto l'alto numero di esemplari catturati, risulta ovvio che la banca dati turca dello squalo capopiatto detiene un numero significante di individui di H. griseus catturati nel Mediterraneo orientale, il che emerge sia da studi storici che contemporanei. Il rapporto tra i sessi negli esemplari di H. griseus esaminati e di 1:2,61 a favore delle femmine. L'analisi degli attrezzi da pesca usati per 72 esemplari ha evidenziato che la maggior parte di essi e stata catturata con la senna a sacco, seguita da diversi tipi di attrezzi da pesca di fondo. La lunghezza totale degli esemplari catturati variava da 50 a piu di 650 cm per entrambi i sessi. Tuttavia, due gruppi di dimensioni sono risultati dominanti, ossia fra i 250 e i 350 cm, e fra i 350 e i 450 cm di lunghezza totale.
Three species of hexanchiform sharks belonging to two families and 12 species of squaliform sharks belonging to three families were recorded in fish landing site surveys in eastern Indonesia. Of ...these, the Squalidae were the most abundant species landed, with Squalus hemipinnis, Squalus edmundsi and Squalus montalbani contributing 0·4, 0·4 and 0·5% to the total number of sharks recorded in a 5 year survey of Indonesian fish landing sites. In comparison, the hexanchid Hexanchus griseus contributed the largest percentage to the total shark biomass. For many species, the majority of the catch consisted of immature fishes, which had not yet been able to reproduce. The data presented in this article are the first biological data reported on most of these shark species and are thus vital for fisheries managers and conservation assessors.
Hexanchiformes is regarded as a monophyletic taxon, but the morphological and genetic relationships between the five extant species within the order are still uncertain. In this study, we determined ...the whole mitochondrial DNA (mtDNA) sequences of seven sharks including representatives of the five Hexanchiformes, one squaliform, and one carcharhiniform and inferred the phylogenetic relationships among those species and 12 other Chondrichthyes (cartilaginous fishes) species for which the complete mitogenome is available. The monophyly of Hexanchiformes and its close relation with all other Squaliformes sharks were strongly supported by likelihood and Bayesian phylogenetic analysis of 13,749 aligned nucleotides of 13 protein coding genes and two rRNA genes that were derived from the whole mDNA sequences of the 19 species. The phylogeny suggested that Hexanchiformes is in the superorder Squalomorphi, Chlamydoselachus anguineus (frilled shark) is the sister species to all other Hexanchiformes, and the relations within Hexanchiformes are well resolved as Chlamydoselachus, (Notorynchus, (Heptranchias, (Hexanchus griseus, H. nakamurai))). Based on our phylogeny, we discussed evolutionary scenarios of the jaw suspension mechanism and gill slit numbers that are significant features in the sharks.
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