Using climate downscaling to hypothesise impacts on apex predator marine ecosystem dynamics

Abstract

Climate downscaling studies help to connect global predictions and projections with regional dynamics and generate a better understanding of past and future conditions. Adding ecological variables and trophic relationships into the climate equation is challenging since there are few clear connections. The present study is an exploratory data analysis to explain dusky dolphin (Lagenorhynchus obscurus) encounter rate patterns in Admiralty Bay, New Zealand. During 2001–2006, dolphin encounter rate in winter decreased from 6 to 0.8 groups/h and the proportion of dolphin groups observed feeding decreased from 80% to 38% in Inner Admiralty Bay. These trends generally corresponded to cooler and moderate El Niño Southern Oscillation years, lower sea surface height, southwesterly winds, increased surface mixing and decreased sea surface salinity. To fully grasp the significance of these relationships and potential impact(s) on dolphin population trends, directed long-term studies that synthesise dolphin, prey, water quality, anthropogenic pressures and climatic information into regional climate-ecosystem models are needed.