Environmental and anthropogenic factors affecting the increasing occurrence of shark-human interactions around a fast-developing Indian Ocean island [+ Corrigendum]

Understanding the environmental drivers of interactions between predators and humans is critical for public safety and management purposes. In the marine environment, this issue is exemplified by shark-human interactions. The annual shark bite incidence rate (SBIR) in La Reunion (Indian Ocean) is among the highest in the world (up to 1 event per 24,000 hours of surfing) and has experienced a 23-fold increase over the 2005-2016 period. Since 1988, 86% of shark bite events on ocean-users involved surfers off the leeward coast, where 96% of surfing activities took place. We modeled the SBIR as a function of environmental variables, including benthic substrate, sea temperature and period of day. The SBIR peaked in winter, during the afternoon and dramatically increased on coral substrate since the mid-2000s. Seasonal patterns of increasing SBIR followed similar fluctuations of large coastal shark occurrences (particularly the bull shark Carcharhinus leucas), consistent with the hypothesis that higher shark presence may result in an increasing likelihood of shark bite events. Potential contributing factors and adaptation of ocean-users to the increasing shark bite hazard are discussed. This interdisciplinary research contributes to a better understanding of shark-human interactions. The modeling method is relevant for wildlife hazard management in general

Environmental and anthropogenic factors affecting the increasing occurrence of shark-human interactions around a fast-developing Indian Ocean island

Abstract Understanding the environmental drivers of interactions between predators and humans is critical for public safety and management purposes. In the marine environment, this issue is exemplified by shark-human interactions. The annual shark bite incidence rate (SBIR) in La Réunion (Indian Ocean) is among the highest in the world (up to 1 event per 24,000 hours of surfing) and has experienced a 23-fold increase over the 2005–2016 period. Since 1988, 86% of shark bite events on surfers involved ocean-users off the leeward coast, where 96% of surfing activities took place. We modeled the SBIR as a function of environmental variables, including benthic substrate, sea temperature and period of day. The SBIR peaked in winter, during the afternoon and dramatically increased on coral substrate since the mid-2000s. Seasonal patterns of increasing SBIR followed similar fluctuations of large coastal shark occurrences (particularly the bull shark Carcharhinus leucas), consistent with the hypothesis that higher shark presence may result in an increasing likelihood of shark bite events. Potential contributing factors and adaptation of ocean-users to the increasing shark bite hazard are discussed. This interdisciplinary research contributes to a better understanding of shark-human interactions. The modeling method is relevant for wildlife hazard management in general

Dynamics of weakly aggregated colloidal particles - discussion

We discuss the behaviour of the dynamics of colloidal particles with a weak attractive interparticle interaction that is induced through the addition of polymer to the solvent. We briefly review the description of their behaviour in terms of the jamming phase diagram, which parametrized the fluid–to–solid transition due to changes in volume fraction, attractive energy or applied stress. We focus on a discussion of ageing of the solid gels formed by these colloid–polymer mixtures. They exhibit a delayed collapse induced by gravity. The time evolution of the height of the sediment exhibits an unexpected scaling behaviour, suggesting a universal nature to this delayed collapse. We complement these measurements of the scaling of the collapse with microscopic investigations of the evolution of the structure of the network using confocal microscopy. These results provide new insight into the origin of this ageing behaviour

Targeted Catch-and-Release of Prohibited Sharks: Sand Tigers in Coastal Delaware Waters

The popularity of recreational shark fishing appears to be on the rise in recent years, with current policies often failing to address the direct targeting of protected species in this sector. Examination of catch trends from the past decade revealed that more than 66 million sharks were caught by recreational anglers along the U.S. eastern coast alone, including more than 1.2 million prohibited species. Using Sand Tigers Carcharias taurus captured by volunteer anglers as a case study to evaluate post-release mortality, 33 individuals were fitted with external acoustic tags and passively tracked using an array of acoustic receivers. Although rates of internal hooking and gear retention were high (57% and 60%), short-term post-release mortality was relatively low (6%) and was heavily influenced by hook location and retention. Given the dramatic increase in the range and extent of recreational fishing targeting prohibited species, even relatively low mortality rates may still pose a significant threat to recovery