We describe fine-scale interactions between dusky dolphins and mussel farms in Admiralty Bay, New Zealand. We examined dusky dolphin presence in nearshore mussel farms, coordinated feeding behaviours in and near mussel farms, and long-term changes in regional population abundance. Sampling methods included boat-based surveys, focal follows, underwater observations, and photoidentification. Correcting for area, dusky dolphins spent significantly less time inside mussel farms versus outside mussel farms and other nearshore areas (both PB0.001). Prey balls entered or moved adjacent to mussel farms during 2/52 feeding bouts, after which dusky dolphin feeding behaviour ceased. Total estimated abundance during winter 2005Á2006 was 712 (95% CI: 511Á1134) with a declining trend in annual abundance after 2003. Results suggest that: (1) dusky dolphins rarely use mussel farms; (2) mussel farms may hinder coordinated feeding strategies; and (3) the number of dusky dolphins using this foraging habitat varies between years and may be declining.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.