1,720,995 research outputs found
Figure 3 in Occurrences of large sharks in the open waters of the southeastern Mediterranean Sea
No full textFigure 3. Map depicting capture locations of blue sharks (Prionace glauca) in the southeastern Mediterranean large pelagic fisheries during 1998–2005.Published as part of Damalas, Dimitrios & Megalofonou, Persefoni, 2012, Occurrences of large sharks in the open waters of the southeastern Mediterranean Sea, pp. 2701-2723 in Journal of Natural History 46 (43-44) on page 2709, DOI: 10.1080/00222933.2012.716864, http://zenodo.org/record/520223
Figure 4 in Occurrences of large sharks in the open waters of the southeastern Mediterranean Sea
No full textFigure 4. Map depicting capture locations of mackerel shark species (Lamniformes) in the southeastern Mediterranean large pelagic fisheries during 1998–2005.Published as part of Damalas, Dimitrios & Megalofonou, Persefoni, 2012, Occurrences of large sharks in the open waters of the southeastern Mediterranean Sea, pp. 2701-2723 in Journal of Natural History 46 (43-44) on page 2709, DOI: 10.1080/00222933.2012.716864, http://zenodo.org/record/520223
Figure 1 in Occurrences of large sharks in the open waters of the southeastern Mediterranean Sea
No full textFigure 1. Map of the study area in the southeastern Mediterranean Sea. Fishing locations are indicated by crosses (1998–2001) and solid triangles (2003–2005). Shaded marine regions designate potential Exclusive Economic Zones (EEZ) as provided by Flanders Marine Institute (VLIZ), available at: http://www.vliz.be/vmdcdata/marbound/. To date, very few Mediterranean countries have claimed an EEZ.Published as part of Damalas, Dimitrios & Megalofonou, Persefoni, 2012, Occurrences of large sharks in the open waters of the southeastern Mediterranean Sea, pp. 2701-2723 in Journal of Natural History 46 (43-44) on page 2703, DOI: 10.1080/00222933.2012.716864, http://zenodo.org/record/520223
Incidental catch and estimated discards of pelagic sharks from the swordfish and tuna fisheries in the Mediterranean Sea
No full textLarge pelagic sharks are caught incidentally in the swordfish and tuna fisheries of the Mediterranean Sea. In our study, twelve shark species were documented as bycatchover three years from 1998 to 2000. Blue shark (Prionace glauca) was the predominant species in all gears and areas examined. Shortfin mako (Isurus oxyrinchus), common threshershark (Alopias vulpinus), and tope shark (Galeorhinus galeus) were the next most abundant shark species—found in more than half of the areas sampled. Catch composition varied both in the areas and gears investigated. Sharks represented 34.3% in weight of total catches sampled in theAlboran Sea and 0.9% in the Straits of Sicily. Higher shark catches were observed in the swordfish longline fishery, where a nominal CPUE value reached 3.8 sharks/1000 hooks in the Alboran Sea. Size distribution by fishing gear varied significantly. Albacore longline catches consisted mainlyof juveniles, whereas subadult and adult specimens were more frequent in the swordfish longline and driftnetfishery. The percentage of sharks brought onboard alive was exceptionally high; only 5.1% of the specimens died. Few discards (seven blue shark) were recorded in the Greek longline fleet during onboard sampling in the Aegean S
Habitat Mapping Of Blue Shark In The Eastern Mediterranean Sea: Application Of Generalized Additive Models On Commercial Fishery By-Catch
No full textBlue sharks (Prionace glauca, Linnaeus 1758), are repeatedly caught in the surface drifting longline fisheries throughout the eastern Mediterranean Sea. Based on a dataset derived from the Greek and Cypriot commercial fisheries, targeting swordfish during 1998-2005, we applied an information theoretic generalized additive model approach, modeling separately: (1) the probability of making a catch and (2) the positive catch rates. Analyses suggested... (+++)JRC.G.4 - Maritime affair
Discovering where bluefin tuna, Thunnus thynnus, might go: using environmental and fishery data to map potential tuna habitat in the eastern Mediterranean Sea
Full text linkBased on a dataset derived from commercial fisheries in the eastern Mediterranean Sea in 1998-2005, we applied generalized additive models (GAMs) to investigate the relative influence of a range of environmental factors on catch rates of Atlantic bluefin tuna (Thunnus thynnus Linnaeus, 1785). GAM analyses were conducted by separately modelling (1) the probability of making a catch (encountering a school), and (2) the positive catch rates (school size). Results suggested intra-annual variations in tuna distribution and revealed interesting associations with some environmental features, lunar periodicity being the most distinctive one... (+++)JRC.G.4 - Maritime affair
Aging and life history traits of the longnose spiny dogfish in the Mediterranean Sea: New insights into conservation and management needs
No full textAging chondrichthyans has been characterized as a slow and difficult process, but at the same time it is considered of fundamental importance for the holistic management and conservation of their populations. This study aims to assess the age and growth of the longnose spurdog S. blainville, to correlate the results to the species’ biological features and to compare them with those reported in previous studies that used different aging methods. By counting the growth bands on the enamel surface of the dorsal fin spines, age was estimated in 569 out of 810 individuals that were taken as by-catch from commercial fisheries in the Mediterranean Sea during an 8-year period. Spine morphometrics revealed sexual dimorphism as far as spine length, spine base width and spine weight are concerned. The between-sex differences were also reflected in the length-weight relationships, in the gonadosomatic (GSI) and hepatosomatic (HSI) indices, and in the condition factor (K). All three somatic indices differed significantly among maturity stages, seasons or age classes. The reproducibility of the age readings was considered high based on the estimated CV and APE precision indices. Age bias plots also indicated no significant intra- and small inter-reader variation. The estimated VBGF parameters were: L∞ = 1097.3 mm, k = 0.03 yr−1 and t0 = −5.58 yrs for females, and L∞ = 665.5 mm, k = 0.08 yr−1 and t0 = −3.35 yrs for males. Likelihood ratio tests showed that all growth parameters were statistically significantly different between sexes ( 2 = 38.26, df = 3, P < 0.001). Females reached higher longevity (28 yrs) than males (22 yrs) and
attained maturity at higher age and larger size (T50 = 17 yrs and L50 = 568.1 mm) than males did (T50 = 11.3 yrs and L50 = 460.6 mm). S. blainville seems to be a long-lived shark of slow growth and late maturity, a combination of traits indicating a species of great vulnerability to fishing pressure that can only sustain a low harvest rate
Occurrences of large sharks in the open waters of the southeastern Mediterranean Sea
No full textBased on the most recently updated literature, 25 species of large pelagic sharks inhabit the south-eastern Mediterranean Sea. However, analyzing data collected during 1998 to 2005, we failed to identify even half the number of these species. At least 10 species of large
pelagic sharks were observed. Sharks were the most abundant incidental catch (landed but 6 not specifically targeted, or discarded). Blue shark Prionace glauca was the predominant species, comprising approximately 70% of all large pelagic sharks encountered. Milk shark Rhizoprionodon acutus was observed for the first time in the south-eastern Mediterranean region. Based on their capture location, a series of maps depicting the spatial distribution of large pelagic sharks is provided. It seems as if currently the continuity of the presence of some species in the region may be questionable or that some species may have become extremely rare to be detected in the course of a conventional monitoring survey.JRC.G.4 - Maritime affair
Estimación de la edad del bonito del Atlántico en el Mediterráneo Este usando las espinas dorsales y validación del método
Full text linkGrowth parameters were studied in 397 specimens of the Atlantic bonito caught in the eastern Mediterranean Sea (Aegean and Ionian Seas) ranging from 7.2 to 72.5 cm in fork length and from 2 to 5400 g in total weight. The study of the growth bands in spine sections showed that one translucent ring is formed annually during the cold season. The growth parameters estimated (L∞ = 82.99 cm, K = 0.24, t0 = -0.77) express the growth of the species more realistically than previous studies in the Mediterranean Sea and the Atlantic Ocean.Se estudiaron los parámetros de crecimiento en 397 especimenes de bonito del Atlántico capturados en el Mediterráneo Este (mares Egeo y Jónico) entre 7.2 y 72.5 cm de longitud total y de 2 a 5400 g de peso total. El estudio de las bandas de crecimiento en secciones de espinas mostró que anualmente, durante la estación fría, se forma un anillo translucido. Los parámetros de crecimiento estimados (L∞ = 82.99 cm, K = 0.24, t0 = -0.77) expresan el crecimiento de la especie de manera más realista que en previos estudios en el Mediterráneo y el Atlántico
Biología reproductiva y desarrollo embrionario de Squalus blainvillei en el este del mar Mediterráneo
Full text linkA total number of 526 Squalus blainvillei was sampled from the bottom trawl and bottom longline catches in the eastern Mediterranean Sea from December 2004 to December 2009. Females outnumbered males and the overall sex ratio was 1.26:1. Females ranged from 182 to 779 mm in total length and males from 180 to 799 mm. Both females and males showed allometric growth (b > 3) and we found statistically significant differences in the relationship between length and weight. Out of the specimens examined, 36% of females and 63% of males were sexually mature. Males reached sexual maturity at smaller sizes than females. The smallest sexually mature female was 523 mm in total length, while the smallest sexually mature male was 425 mm in total length. Mean length at 50% maturity was estimated at 564.4 mm for females and 457.7 mm for males. Sexually mature specimens of both sexes with mature gonads and high GSI were present in high proportions in every season of the year, which indicates a continuous reproductive cycle. Ovarian oocytes continued to develop throughout gestation. Females carrying near-term embryos had large, equally developed ovarian oocytes, which suggests that they ovulate soon after parturition. Ovarian fecundity ranged from 1 to 7 and uterine fecundity ranged from 1 to 6. Embryo length and yolk sac weight were negatively correlated.Un total de 526 Squalus blainvillei procedentes de pescas de arrastre de fondo y palangres de fondo se muestrearon en el este del Mar Mediterráneo, desde diciembre de 2004 hasta diciembre de 2009. Las hembras excedieron en número a los machos y el cociente de sexos fue 1.26:1. Las hembras midieron entre 182 y 779 mm de longitud total y los machos de 180 a 799 mm. Tanto machos como hembras mostraron un crecimiento alométrico (b > 3), pero se encontraron diferencias estadísticamente significativas en la relación talla y peso. De los especímenes examinados, el 36% de las hembras y el 63% de los machos eran sexualmente maduros. Los machos alcanzaron la madurez sexual a tamaños más pequeños que las hem- bras. La hembra sexualmente madura de menor talla tenía una longitud total de 523 mm, mientras que el macho sexualmente maduro más pequeño tenía una longitud total de 425 mm. La talla media al 50% de madurez, se estimó en 564.4 mm para las hembras y en 457.7 mm para los machos. Los especímenes de ambos sexos sexualmente maduros, con gónadas maduras y alto GSI estuvieron presentes en elevadas proporciones en todas las estaciones del año, indicando un ciclo reproductivo continuo. Los oocitos ováricos continuaron desarrollándose durante la gestación. Las hembras que llevaban embriones desarrollados tenían grandes oocitos ováricos igualmente desarrollados, lo que hace pensar que ovulan pronto después del parto. La fecundidad ovárica varió de 1 a 7 y la fecundidad uterina de 1 a 6. La longitud de los embriones y el peso del saco vitelino estuvieron correlacionados negativamente
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