1,720,976 research outputs found
The effect of Mistral (a strong NW wind) episodes on the occurrence and abundance of Atlantic bluefin tuna (Thunnus thynnus) in the trap fishery of Sardinia (W Mediterranean)
Full text linkFrom April to June Atlantic bluefin tuna, Thunnus thynnus, migrate along the western Sardinian coastline in a southward direction, where they are intercepted by the trap fishery. Fishermen claim that Mistral episodes facilitate the entry of tuna schools towards the traps, thus increasing capture rates. To test the fishermen’s hypothesis we conducted underwater visual counts of tuna in the trap chambers and analysed these data under the effect of wind. The results indicate a “stair-step” pattern in the abundance of tuna, demonstrating that major increases in abundance are associated with the Mistral. The second analytical approach involved a longer time scale to test whether higher Mistral occurrences corresponded to periods when higher captures were recorded. Using a linear regression model we found a significant correlation (p15 knots seemed to have a negative effect on captures. This pattern may be caused by wind-induced advection of coastal waters generating a physical boundary that may have had a deterrent effect on tuna schools
Geographic variation of body morphology of the Atlantic bluefin tuna, (Thunnus thynnus, Linnaeus, 1758)
No full textGeometric morphometric methods were used to explore body shape morphology in 260 Atlantic bluefin tuna, Thunnus thynnus, collected in Sardinia (Western Mediterranean) during the breeding phase and in the Bay of Biscay (North Eastern Atlantic) during the feeding phase. The shape of each specimen was captured by high resolution digital images and recording the 2-D coordinates of seven morphological landmarks. A general procruste analysis (GPA) was applied in order to eliminate any morphological variations resulting from size, position or orientation of specimens. A thin plate-spline (TPS) method was then used to provide a graphical representation of the shape conformation between two sets of data. Results of the regression model between the direct and indirect measurements accounted for a R2 = 0.98. The Principal Components Analysis shows differences linked to the two sampling areas, accounting for 37% and 19.97% of the body shape variation in the first (PC1) and second (PC2) principal component, respectively. Specifically, the deformation grid projection highlights the major differences regarding the anterior-ventral part of the body (landmark 5-6-7). These differences might not necessarily be linked to an actual population substructure. Instead, it was hypothesized that such body shape differences were due to the diverse life phases during which specimens were collected, since the reproductive specimens show a 'potbellied' shape, which was larger than for the feeding specimens that showed a 'slimmer' shape. Analyses of likely sexual dimorphism conducted on Sardinian specimens did not reveal any significant differences; whereas body shape differences related to the pre- and post-reproductive sizes were detected
Analysis of Atlantic bluefin tuna catches from the last Tonnara in the Mediterranean Sea: 1993–2010
No full textIn the last 20 years, several factors have heavily impacted the Atlantic bluefin tuna fishery. They include management policies, market changes, the ban of the drift-net fishery, expansion of the modern purse seine fleet, and implementation of a stock recovery plan. To enhance current knowledge about the population's status, we conducted a long-term analysis (1993–2010) of scientific data and standardized catch-per-unit-of-effort (CPUE) from the traditional trap fishery of Sardinia (Western Mediterranean, Italy), which is the last active bluefin trap fishery in the Mediterranean. We detected a significant increase of the standardized CPUE and a significant decrease in mean weight over time. Cluster analysis conducted on 29,000 specimens revealed three different size groups that were distinct by time period: the 1993–1995 period was characterized by a significant presence of large bluefin; a decrease in mean weight occurred in the 1996–2006 period; and 2007–2010 was characterized by the prevalence of young adults in the history in the trap fishery. This trend, which needs to be confirmed over longer time and spatial scales, raises some ecological questions. In particular, is the occurrence of these young adults a consequence of changes in the migratory behavior of bluefin tuna in the Mediterranean, or does it reflect the actual demography of this population? The results of this study emphasize that data from traditional traps provide valuable long term scientific information about population parameters through time, and thus the use of traps as monitoring stations should continue in the future
Physiologic responses to stress and changes in Atlantic Bluefin Tuna (T. thynnus) meat color during trap fisheries capture and processing in Sardinia (W. Mediterranean)
No full textThis study investigated plasma cortisol, lactate, and glucose as descriptors of hematological stressors; while the RGB color model using the percentage of monochromatic channels Red (Rp), Green (Gp), and Blue (Bp) was used for the analysis of muscular tissue of the Atlantic bluefin tuna, Thunnus thynnus. The experimental design provided a comparison of stressors and color channels Before and After the stress state and the analysis of variability of monochromatic channels for Fresh and Frozen specimens
collected at three time intervals. Results showed a rapid accumulation of cortisol levels (from 73.3 ± 9.5 to 148.0±21.2 ng/mL), lactate (from 5.7±2.9 to 17.0±2.2 μmol/mL), and glucose (from 83.5± 8.0 to 128.6 ± 19.3 mg/dL; p < 0.05). The colorimetric analysis highlighted that this accumulation did not in fact affect the color variability of muscle. Analysis of variance carried out to test the effects of color variability in Fresh samples showed significant differences for Rp,Gp, and Bp channels (p<0.05), whereas no differences were found in Frozen samples. Highly significant differences (p < 0.001) were found comparing Fresh and Frozen for Rp and Bp, indicating a drop of these channels under diverse treatments
HARVESTING , HANDLING PRACTICES AND PROCESSING OF BLUEFIN TUNA CAPTURED IN THE TRAP FISHERY :
No full textQuEChERS method for the determination of PAH compounds in Sardinia sea urchin (Paracentrotus lividus) roe,using gas chromatography ITMS-MS analysis
No full textSea urchin roe (Paracentrotus lividus) is an excellent biomarker and it has been usedas a test for toxicology study of chemical pollution of restricted marine areas, infact,unlike mussels which filter water it feeds mainly of micro and macro algae. Therefore itnot influenced by sea tide and meets better the situation of local pollution. A modifiedQuEChERS extraction method coupled with gaschromatography iontrap massspectrometry (ITMS/MS) analysis has been used to set up a method for thedetermination of 17 polycyclic aromatic hydrocarbons (PAHs) in Paracentrotus lividussea urchin roe. A method validation was performed and the following parameters havebeen determined: instrument limit of detection (LOD) and of quantification (LOQ),precision, recovery and linearity. The method carried out showed good LOD under 1.5ug/kg and LOQ under 5 ug/kg for all PAHs studied and were in close agreement withquality criteria described in the Commission Regulation (EC) No 333/2007 concerningthe PAH benzo[a]pyrene in foodstuffs. Precision and linearity were in accordance withEC SANCO/10684/2009 values. For all PAHs recoveries ranged from 72 to 119 %,with RSD ranging from 3 to 17 % in the most unfavorable case
Effect of two different habitats on spine and gonad colour in the purple sea urchin Paracentrotus lividus
No full textThis study investigates the effect of different Mediterranean habitats on spine and gonad colouring and gonadal index in the purple sea urchin ea and the gonad index of the purple sea urchin Paracentrotus lividus (Echinodermata: Echinoidea). Specimens were collected in winter 2012 in Posidonia oceanica meadows and rocky bottom areas at two sites in Southern Sardinia (Italy, Tyrrhenian Sea). Colorimetric analyses of spines and gonads were conducted with a digital colorimeter using CIELAB colour spaces, which defines the colour in terms of three coordinate values: lightness (L*), redness (a*) and yellowness (b*). Lightness and redness of the spines differed significantly between habitats, whereas colour spaces of the gonads did not. A careful analysis of the gonad index showed it to be significantly affected by habitat, registering higher values in rocky bottom locations. In conclusion, it seems that habitat does affect spine colour but not gonad colour. Spine colour seems to be site-dependent, whereas the gonad index depends solely on the habitat
GC–ITMS analysis of PAH contamination levels in the marine sea urchin Paracentrotus lividus in Sardinia
No full textThis paper describes the results of a two-year monitoring study examining the pollution of the sea urchin
Paracentrotus lividus by polycyclic aromatic hydrocarbons (PAHs) in Sardinia. GC–ITMS analysis of sea
urchin gonads showed the presence of 11 and 12 PAHs in the samples of Capo Pecora, and Capitana,
respectively. Fluorene, naphthalene and its two degradation products, 1-methyl-naphthalene, and
2-methyl-naphthalene, were detected in all samples analyzed. The RPAH residues showed a similar trend
over the two-year sampling period. Furthermore, the residues in the first year were slightly higher than in
the second year. The information obtained by the multivariate statistical analysis PLS-DA allowed for the
determination of samples based on field site and varying habitat types (rocky reef, and Posidonia seabed).
The results of this study showed that Posidonia sea urchins are contaminated by high molecular weight
PAHs and that Capitana samples are more contaminated due to a higher level of human activity in the
area
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
