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Scottish Marine and Freshwater Science Reports

Formal report series, containing results of research and monitoring carried out by Marine Scotland Science

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Review Of Demographic Parameters And Sensitivity Analysis To Inform Inputs And Outputs Of Population Consequences Of Disturbance Assessments For Marine Mammals

Scottish Marine and Freshwater Science Vol 11 No 14
The interim Population Consequence of Disturbance (iPCoD) is a framework that allows individual-level effects from disturbance to be scaled to population-level impacts. This approach is parameterised by published figures for specific UK populations or derived from the literature for a given species. The original iPCoD model was developed in 2013, with subsequent reviews of the recommended demographic input parameters in 2014 and 2017. This current report by SMRU Consulting establishes the most up-to-date information on five key species of UK marine mammal (harbour porpoise, bottlenose dolphin, minke whale, harbour seal and grey seal) for use in the iPCoD model.

The report also examines the sensitivity of model output to potential misspecification in the various input parameters that are obtained via expert elicitation. Two approaches were used in the sensitivity testing: the effect of changing the value of a single parameter independently of the others and the effect of adjusting all the demographic parameters systematically to compare scenarios with the same population trajectory but different combinations of demographic parameters. The observed sensitivity to misspecification is complex, however, in general, the demographic parameter most sensitive to this issue was pup/calf survival. However, the sensitivities identified were only apparent at relatively high (and somewhat unrealistic) levels of impact, and therefore SMRU Consulting conclude that the metric of counterfactual of population size, which is presented in impact assessments, is robust to misspecification in demographic rates. Several criteria are still to be explored, such as the sensitivity of alternative output metrics, a wider range of impact scenarios and the effect of any density-dependence. Future directions and recommendations for the iPCoD approach are also suggested.

The updated demographic parameters will improve assessments, and will now be available in time for the upcoming ScotWind leasing round. Where the sensitivity analysis has identified sources of variability and uncertainty in outputs, this will aid interpretation of assessments by advisors and decision makers.

The project was undertaken by SMRU Consulting and funded by Scottish Government.

doi: 
10.7489/12331-1
Citation: 
R R Sinclair, C E Sparling and J Harwood. 2020. Review Of Demographic Parameters And Sensitivity Analysis To Inform Inputs And Outputs Of Population Consequences Of Disturbance Assessments For Marine Mammals. Scottish Marine and Freshwater Science Vol 11 No 14, 74pp. DOI: 10.7489/12331-1

Data and Resources

FieldValue
Publisher
Modified
2020-08-03
Release Date
2020-07-29
Identifier
f13db0ec-6fcb-403b-a97c-31c35c7cec15
Spatial / Geographical Coverage Location
Scotland
License
UK Open Government Licence (OGL)
Data Dictionary

The evaluation of the sensitivity of outputs to misspecification of demographic parameters focused on the ratio output metric of the counterfactual of population size (the median of the ratio of the impacted to un-impacted population size across all simulated matched replicate pairs). This was felt to be more appropriate than the ratio of the impacted to un-impacted growth rates due to the nature of the impact on marine mammals, with disturbance during discrete periods of construction activity rather than a continuous level of impact over an extended period. Two approaches were used in the sensitivity testing: The effect of changing the value of a single parameter independently of the others (this was done for all species except grey seal) and the effect of adjusting all the demographic parameters systematically to compare scenarios with the same population trajectory but different combinations of demographic parameters.

Contact Name
Marine Scotland
Contact Email
Public Access Level
Public