We are delighted to announce the public release of a new version of the iPCoD code!
In collaboration with John Harwood, SMRU Consulting have been hard at work recently developing and testing the iPCoD version 4 code. The iPCoD framework was produced to assess and quantify the potential consequences for marine mammal populations of any disturbance and/or injury that may result from offshore energy developments. It has been designed to use the kinds of information that are likely to be provided by developers in their Environmental Statements and Habitats Regulations Assessments.
The new iPCoD version 4 code incorporates updated transfer functions for the effects of permanent threshold shifts (PTS) (see details below) as well as new summary outputs. The new outputs compare between the impacted and un-impacted population trajectories and provide a much improved, user-friendly way to view the results of the simulations.
In addition, bugs that had been identified and reported in the v3 code have been investigated and addressed. SMRU Consulting rely on user participation to identify bugs and develop version updates, so many thanks to those users that have been in touch to highlight bugs they have encountered.
Updated PTS Transfer Functions
The interim PCoD framework uses on expert elicitation to parameterise poorly understood relationships within the model. One such relationship is the effect of a PTS in hearing on an animals ability to survive and reproduce. An expert elicitation was conducted in 2013, however, given new data on threshold shifts and effects on marine mammals, a new expert elicitation was conducted in March 2018 to update the iPCoD framework. The new expert elicitation considered the effect of PTS in harbour porpoise, bottlenose dolphins, grey and harbour seals.
A full report on this expert elicitation on PTS impacts is now available here: Booth & Heinis 2018 – Updated PTS Elicitation
Here are a few highlights from the report:
- PTS does not mean an animal is deaf by default! It means the animal experiences a reduction in hearing sensitivity in a specific frequency range.
- The effect of PTS on vital rates will be driven by the magnitude and the frequency band of the PTS.
- Reduced hearing ability does not necessarily mean a less fit animal.
- A 6 dB PTS in the 2-10 kHz band was considered to be viable consequence of exposure to broadband impulsive noise (like pile driving or airgun blasts) but was unlikely to have a large effect on survival or fertility.
- The new expert elicitation means that the predicted effect size (from PTS) is much smaller than in the previous elicitation. This will result in smaller PTS effects on vital rates in the iPCoD model (i.e. all other things being equal, in the iPCoD model, PTS will have a smaller impact on animals, and consequently the population – than in the original version).
In addition to this, a second expert elicitation workshop was conducted in June 2018 to parameterise the relationship between disturbance and vital rates. The results of this expert elicitation haven’t yet been incorporated into iPCoD but will be included in v5 of the code which will likely be released in the autumn.