Abstract:
Blue sharks are oceanic epipelagic sharks in temperate and tropical waters. They are found off the coasts of all continents except Antarctica, in waters temperatures ranging from 12 to 20 °C and 7 to 25 °C. Indeed, water temperature is one of the most influential factors in the physiological performance and behaviour of marine ectothermic sharks (e.g. blue sharks), which are organisms that cannot regulate their body temperature internally. The effects of changes in ocean temperature can affect their physiological responses, such as growth, feeding, acid-base balance, and metabolism, with significant changes in their energy budget and their horizontal and vertical distribution patterns. To broaden the study and provide insight into the behaviour of marine ectotherms in relation to ocean temperature, particularly the behaviour of the blue shark, the central question addressed in this study is how the thermal niche and spatial distribution of blue sharks vary with ocean temperature. In this study, we determined the thermal niche of blue sharks, including how ocean temperature affects their swimming performance and spatial distribution. For the experiment setup, blue shark tag data recorded by accelerometers and satellite transmitters (PSAT- pop-up satellite transmitters) in the North Atlantic Ocean were used. From the extensive study carried out, the results showed that blue sharks were most active at ocean temperatures of 21.86 ºC with a temperature tolerance of 10-22 ºC; meanwhile, they spend most of their time at temperatures ranging from 13 ºC to over 25 ºC. From both short and long-term studies, the thermal niche was estimated to be between 18 ºC to 21 ºC. On the other hand, the time spent in each depth range showed that they were mainly in the upper 50 m. Their swimming performance showed that their horizontal distribution followed ocean temperature, and they will become more concentrated in high latitudes with global warming.
Description:
A Thesis submitted to the West African Science Service Center on Climate Change and Adapted Land Use and Universidade Técnica do Atlântico, Cabo Verde in partial fulfillment of the requirements for the Master of Science Degree in Climate Change and Marine Science
