Here, we examined space use and residency patterns of 14 great hammerheads Sphyrna mokarran, 13 bull sharks Carcharhinus leucas, and 25 nurse sharks Ginglymostoma cirratum in proximity to the coastal metropolis of Miami, Florida, using passive acoustic telemetry. Sharks are upper trophic level predators in virtually all marine environments, but if and how their behaviors are influenced by coastal urbanization remains understudied. Understanding and ultimately predicting how marine organisms will respond to urbanization is central for effective wildlife conservation and management in the Anthropocene. The interplay of tides and temperature, and how these varied across diel and daily scales, dynamically influenced stingray habitat use consistently between three species in an offshore atoll. Habitat use also varied over the tidal cycle with stingrays spending a higher proportion of time in the lagoon during the lowest tides, when movement on the flats were constrained due to shallow waters. Temperature was also found to influence stingray movements, with individuals preferring the deeper and more thermally stable lagoon habitat when extreme (hot or cold) temperature events were observed on the flats. Habitat use varied over the diel cycle, but was inconsistent between individuals.
Individuals were detected in the atoll year-round, but the extent of their movement and use of multiple habitats increased in the warmer NW-monsoon season.
Crepuscular life drivers#
This was to determine if habitat use varied over daily, diel and tidal cycles and to investigate the environmental drivers behind these potential temporal patterns. Passive acoustic telemetry was used to track the movements of 60 stingrays at a remote and environmentally heterogeneous atoll in Seychelles. Understanding the contextual and relative influences of these abiotic factors is important in prioritizing management plans, particularly for vulnerable faunal groups like stingrays. Specifically, tides may alter the physical and biological characteristics of an ecosystem while changes in temperature can cause ectothermic species to behaviorally thermoregulate. While research on the behavior of elasmobranchs during dark periods has been increasing, many knowledge gaps remain and we present a set of research priorities to assist in the development of future investigations.Ībiotic factors often have a large influence on the habitat use of animals in shallow marine environments. Thus, generalizations about increased elasmobranch activity during dark periods are currently not supported. We did not find any particular habitat type consistently supporting increased activity during dark, nor did we find evidence that higher trophic level elasmobranchs were more active when dark. No pervasive patterns emerged for increased habitat use or reproductive behaviors during dark. Frequency of foraging and horizontal movement (distance travelled, activity space) were reported as greater only during crepuscular periods in the majority (>50%) of reviewed studies (28 of 43 and 78 of 125 studies, respectively), a pattern not evident during night. A review of 166 studies provided mixed results for widely-assumed increased elasmobranch activity when dark. Here, we review and summarize previous studies on elasmobranch behavior during nocturnal and crepuscular periods focusing on patterns of movement, habitat use, foraging, and reproduction. If this were the case, low-light periods would be of significance to elasmobranch conservation as some anthropogenic activities (night fishing, lighting) could disproportionately impact fitness of species that are more active in the dark. It is also unclear whether dark periods are primarily utilized for the performance of important life-history events, such as mating. However, this assertion has not been critically evaluated. It is commonly assumed that elasmobranchs (sharks, skates, and rays) are most active during dark periods (dawn, dusk, night).
0 kommentar(er)
