Search Results (3)

Animal-borne tags are widely used for tracking and monitoring the movements, behaviour, and ecology of marine animals. Tagging can, however, adversely affect the hydrodynamic force balance and welfare of tagged animals, and consequently, the reliability and accuracy of data, such as by increasing drag, altering swimming characteristics, and reducing the survival rate of tagged animals. Therefore, it is important to understand and quantify the impact of tagging on marine animal hydrodynamics and to optimize the choice of tag and attachment position. In this study, computational fluid dynamics (CFD) modelling is used to simulate the flow around tagged and untagged mako sharks (Lamnidae) across their swim speed range for two dominant tag shapes, tagging sites, and body sizes. The results indicate that fin mounted tags can have a significant impact on shark hydrodynamics and energetic balance, increasing drag between 17.6% and 31.2% for a mako shark (2.95 m fork length) across the range of flow velocities tested (0.5 to 9.1 m/s). In comparison, the optimal tagging site for archival tags attached to the dorsal musculature leads to a minimal increase in drag for the larger sharks (>1.5 m), which becomes considerable for small sharks (1 m fork length; 5.1% to 7.6% increase) and leads to an average energetic cost equivalent to 7% of the daily energetic requirement of an untagged animal. Other aspects of the force balance are considered, which reveal a range of varied and complex effects. Recommendations for animal size thresholds (>1.5 m FL) and refinements of tagging practice are suggested. Full article

The white shark, Carcharodon carcharias, is the main top predator of the present-day Mediterranean Sea. The deep past of C. carcharias in the Mediterranean is witnessed by a rather conspicuous, mostly Pliocene fossil record. Here, we provide a synthesis of the palaeobiology and palaeoecology of the Mediterranean white sharks. Phenetically modern white shark teeth first appeared around the Miocene–Pliocene transition in the Pacific, and soon after in the Mediterranean. Molecular phylogenetic analyses support an origin of the Mediterranean white shark population from the dispersal of Australian/Pacific palaeopopulations, which may have occurred through the Central American Seaway. Tooth dimensions suggest that the Mediterranean white sharks could have grown up to about 7 m total length during the Pliocene. A richer-than-today marine mammal fauna was likely pivotal in supporting the Mediterranean white sharks through the Pliocene and most of the Quaternary. White sharks have seemingly become more common as other macropredators declined and disappeared, notwithstanding the concurrent demise of many potential prey items in the context of the latest Pliocene and Quaternary climatic and environmental perturbations of the Mediterranean region. The overall generalist trophic habits of C. carcharias were likely crucial for securing ecological success in the highly variable Mediterranean scenario by allowing the transition to a mostly piscivorous diet as the regional marine mammal fauna shrank. Full article

Cephalopods, an appreciated seafood product, are common hosts of marine cestodes. The aim of this work is to report visible alive plerocercoids in longfin inshore squid (Doryteuthis pealeii), a cephalopod species commercialized as fresh and whole in Italy. Seventy D. pealeii from the Northwest Atlantic (FAO area 21) were collected and visually inspected. In total, 18 plerocercoid larvae were found in the viscera of 10 host specimens (P: 14.3% 95% CI 7.1–24.7; MI: 1.8, MA: 0.26; range 1–4) and molecularly analyzed targeting the variable D2 region of the large subunit (LSU) rRNA gene and the cytochrome c oxidase subunit I (COI) gene. The molecular characterization allowed to identify all the plerocercoids as Clistobothrium sp., a cestode of the Phyllobothriidae family with Lamnidae sharks as definitive hosts, and cephalopods as second intermediate hosts. These findings represent the first molecular record of Clistobothrium sp. in D. pealeii, thus contributing to elucidate its poorly known life cycle. Even if not affecting consumer’s health, these visible parasites may represent a reason for disgust for consumers. Therefore, the results suggest that Food Business Operators should also check for the presence of these visible parasites during inspection and underline the importance of a correct consumers’ education. Full article