About this Research Topic
Trophic relationships are central in ecology and play a crucial role in species survival, as the availability of food resources varies over time and space, and are typically patchy and unpredictably distributed. Thus, information on the trophic relationships between key-species and top predators is required to understand the structure and function of marine ecosystems. In this context, marine top predators may be used as sentinel organisms, providing a valuable approach into ecosystem conditions and processes as they are closely dependent on the food resources they can find at sea. Marine top predators can be highly sensitive to changes in food availability. Moreover, many taxa (e.g. seabirds, cetaceans) show important interactions with fisheries. Therefore, they can provide early indications of fluctuations in fish stocks and marine environmental health. For instance, inter-annual fluctuations in seabird populations, reproductive performance and foraging behaviour are assumed to be a reliable indicator of natural and local resource availability from both natural and anthropogenic sources. Nevertheless, to be functional, a bioindicator must act in a sensitive response to alterations in the variable for which it is a proxy measure. Therefore, we should select as a bioindicator tool such rapid and sensitive responses as state variables of population size, reproductive success, adult condition status, and diet composition or even include further ecological traits such as foraging ecology or trophic niche width to assess challenging and crucial purposes.
Many marine top predator species are good model species to test several ecological theories that still need validation and support but only recently, with the development of new technology, it became possible to investigate accurately their foraging ecology. For instance, stable isotope analysis (SIA), fatty acids or DNA-based dietary analysis have been used to evaluate trophic relationships, and tracking devices to study species foraging behaviour at sea and spatial distribution.
These techniques are particularly useful in the study of ecological niche mutually in space, time and trophic dimensions, especially when their use is combined. The development of these new approaches to the study of trophic and ecological interactions provides a complementary approach to investigate the structure of marine trophic relationships.
Keywords: marine top predators, predators, trophic relationships, marine, trophic niche, ecology, conservation
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