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 2001Á2006, 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 Nin˜o 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.

Avoidance of mussel farms by dusky dolphins (Lagenorhynchus obscurus) in New Zealand

“…Encounter rate declined from 7.5 groups/h during 2001 to 1.6 groups/h during 2006, with the sharpest decline occurring after 2004. Initial evidence indicates that the observed changes in encounter rate, and perhaps population abundance, are related to changes in sea surface temperature (Srinivasan et al 2012).…”

Dusky dolphin ( Lagenorhynchus obscurus ) habitat use in a mussel farming region and changes over time

“…The decrease in prey herding events observed in this 2011-2012 study may reflect a shift in prey characteristics potentially relating to climate variation (Srinivasan et al 2012), dusky dolphin grouping patterns, and/or an underestimation of prey ball foraging events. In 2002, dusky dolphin groups joined together to form larger feeding aggregations once schooling prey were located (McFadden 2003).…”

Role of Crassicauda sp. in natural mortality of pantropical spotted dolphins Stenella attenuata: a reassessment

“…Cetacean conservation is a pressing issue as many populations worldwide face a number of serious threats, including habitat degradation, interaction with fisheries and climate change (Ross 2006, Lassalle et al 2012, Srinivasan et al 2012. The design and adoption of sound management and conservation plans requires evaluation of how population size may be limited by parasites and pathogens, but knowledge in this area in cetaceans is still scarce due to the cryptic nature of these animals.…”