| Summary: | Dissertação de mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2016 Space use sharing and biological interactions can play an important role in determining individual habitat use and population spatial dynamics. Individuals often aggregate to enhance foraging efficiency, for protection against predators or to increase reproductive success. However, this behaviour also makes them more vulnerable to fishing and overexploitation. Seamounts, in particular, are known to concentrate large aggregations of pelagic reef fishes, and therefore deserve special attention and effective management schemes. The yellowmouth barracuda (Sphyraena viridensis) and the almaco jack (Seriola rivoliana) are two pelagic predators that commonly inhabit these offshore ecosystems in the Azores islands (central North Atlantic), where they are explored by the local artisanal fishing fleet. Yet, until very recently, little was known about their spatial ecology, with most published studies focusing rather on biological /physiological aspects or simply reporting presence records. Therefore, the objective of the present thesis was to use presence-absence datasets collected through passive acoustic telemetry in order to investigate yellowmouth barracuda and almaco jacks space use sharing and activity patterns. After developing a novel quantitative analysis based on fine-scale spatiotemporal overlap and null model randomization tests, evidence of non-random association was found, not only among conspecifics but also between individuals of the two species. Furthermore, tagged animals exhibited both diel and seasonal changes in habitat use. While yellowmouth barracuda are probably diurnal foragers, almaco jacks are probably more active during the night period, which might reduce interspecific competition pressure and increase the tolerance for niche overlap. Although year-round residents, both species seem to overlap more during the spawning season, which takes place from mid spring to late summer. Monthly ...
|
|---|