Declining harbour seal abundance in the Kattegat-Skagerrak and Danish Straits

#Daire Carroll 2025 [e-mail] This repository contains data and code for the manuscript titled: Declining harbour seal abundance in a previously growing metapopulation.

We have compiled data from harbour seal moult surveys carried out throughout the Kattegat-Skagerrak and South Western Baltic Sea since 2003. Through a combination of parametric and non-parametric modelling, we determine changes in seal abundance across the entire region and for subregions representing individual seal colonies.

PV_Trend_Analysis.R is code for modelling popualiton growth based on the data presented in the .csv files below.

Region_Moult_Data.csv is a summary of aerial survey moult counts broken down by sea region throughout the Kattegat-Skagerrak and Danish straits, excluding four Norwegian colonies which were only surveyed in 2016 and 2022 and the Kattegat in 2004.

Subregion_Moult_Data.csv is a summary of aerial survey moult counts broken down by subregion, representing colonies throughout the Kattegat-Skagerrak and Danish straits, excluding four Norwegian colonies which were only surveyed in 2016 and 2022 and the Kattegat in 2004.