Abstract
In South Australia, discrete populations of bottlenose dolphins inhabit two large gulfs, where key threats and population estimates have been identified. Climate change, habitat disturbance (shipping and noise pollution), fishery interactions and epizootic events have been identified as the key threats facing these populations. The Population Consequences of Disturbance (PCoD) framework has been developed to understand how disturbances can influence population dynamics. I used population estimates combined with population specific bioenergetics models to undertake a PCoD assessment, comparing how the two populations respond to the identified regional threats. Populations were modeled over a five year period looking at the influence of each disturbance separately. As expected, extreme disturbance scenarios, in terms of frequency and intensity, had the biggest influence on population trends. However, the magnitude of the effect differed by population, with Spencer Gulf showing a 43% and Gulf St Vincent a 23% decline under high frequency and high impact epizootic scenarios. Epizootic events were seen to have the largest influence on population trends and reproductive parameters for both populations, followed by climate change. Modeling provides insights into how disturbances may affect different populations, and informs management to mitigate their potential effects while there is still time to act. Keywords: Bioenergetics, marine mammals, disturbances, bottlenose dolphins, Bayesian modelling, fecundity, population trends Article Impact Statement: Human induced disturbances impact coastal bottlenose dolphins with varying severity depending on the population and disturbance.
Highlights
Anthropogenic activities have been shown to affect all marine ecosystems, with temperate and tropical coasts seeing the biggest impacts from these pressures (Halpern et al, 2007, 2008, 2015)
Differences in abundance and fecundity from modeled scenarios were compared to the base scenario, were no disturbances were modeled, thereby accounting for natural variation in survival and fecundity within the populations
We modeled the populations for a 5 year period to understand the potential effects of these disturbances over a small time scale, especially given that the impact and extent of these disturbances is highly uncertain and likely to change in the near future (Robbins et al, 2017)
Summary
Anthropogenic activities have been shown to affect all marine ecosystems, with temperate and tropical coasts seeing the biggest impacts from these pressures (Halpern et al, 2007, 2008, 2015). The multitude of disturbances to marine mammal populations include stressors such as climate change, ship and boat traffic, fishing and coastal development, all of which have been shown to impact marine species and populations around the globe (Stock et al, 2018), including those in Australia (Robbins et al, 2017). The destruction of marine habitats, overexploitation, and bycatch of non-target species resulting from fishing activities is often. Anthropogenic activities in coastal environments are likely to increase in the future, intensifying the disturbance to these ecosystems and the organisms that live there (Halpern et al, 2015)
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