Investigating the risk to inshore dolphins from cumulative environmental stressors: A spatial risk assessment approach

Spatial risk assessments using geographic information system (GIS) can be an important decision making tool to rapidly assess risks to threatened species. Spatial modelling of species distributions combined with risk... [ view full abstract ]

Spatial risk assessments using geographic information system (GIS) can be an important decision making tool to rapidly assess risks to threatened species. Spatial modelling of species distributions combined with risk assessments that identify cumulative anthropogenic stressors is particularly useful in marine habitat and can inform reserve planning, invasive species management, marine spatial planning and conservation for threatened species. Most marine megafauna (i.e. dugong, dolphins and whales) have large geographic ranges that overlap with human activities which can threaten their populations. These species are often a priority for conservation. In this study, we used spatial modelling to consider the estimated home range of two inshore dolphin populations (Australian snubfin dolphin, Orcaella henishoni, and Australian humpback dolphin, Sousa shaulensis). Sighting data of the two species were collected from boat-based surveys throughout Cleveland and Halifax Bays off Townsville, Queensland, Australia in 2016. We overlaid the species’ distributions with cumulative threat maps to identify hotspots of high habitat use and threatening factors, to inform a spatial risk assessment. Home range was estimated using ‘adehabitatHR’ package in R statistical software and subsequently plotted in ArcGIS 10.4.1. The resulting threat maps allowed identification of important dolphin areas that are facing significant threats in the Townsville region. These identified areas can be used by the local port and conservation agencies to mitigate risk and disturbance in these hotspot regions. This information provided managers and decision makers with priorities for conservation for the small, localised populations of snubfin and humpback dolphins off Townsville, Queensland, Australia.