Browsing by Author "Kraft, Sebastian Martin"
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- Multi-dimensional dynamics of an elasmobranch assemblage in a marine parkPublication . Kraft, Sebastian Martin; Abecasis, David Maria Aguiar; Mourier, JohannElasmobranchs are marine predators with important ecological and economical roles throughout the world. Many of these species are also vulnerable to anthropogenic impacts, particularly to overfishing. Elasmobranchs are mostly captured as bycatch of other more profitable fisheries and have been historically undermanaged. Presently, overfishing threatens a large proportion of these species with extinction. Marine protected areas (MPAs) are a common management strategy used to protect species and habitats by controlling or prohibiting anthropogenic activities within a delimited area. A critical aspect for their success is the use of reliable information on the movement ecology of species. Nevertheless, elasmobranchs are rarely included in MPA planification as frequently no information on their spatial ecology is available. A common method of collecting this information is passive acoustic telemetry, which allows the long-term tracking of multiple individuals. In this study, a literature review on common methods to analyse acoustic telemetry data was done to guide research efforts. Then, the movement patterns of Dasyatis pastinaca, Rostroraja alba and Raja clavata were studied in the Luiz Saldanha Marine Park by assessing residency, area use, activity, and depth, and evaluating the contribution of spatial data to the conservation of elasmobranchs. Diverse movement patterns were observed, some species-specific, like seasonal residency, and others common to the three species, like diel changes in activity. Finally, fine scale associations and aggregations of D. pastinaca were explored using social network analysis, relating this to the conservation of the species. Although D. pastinaca likely receives the overall lowest amount of protection, demographic differences in Rostroraja alba and Raja clavata suggest protection may be unevenly distributed among conspecifics of these species, favouring immature and male individuals, respectively. These results represent important contributions to the understanding of these species’ spatial ecology and to the management of elasmobranchs of coastal areas.