Dusky dolphin (Lagenorhynchus obscurus) occurrence and movement patterns near Kaikoura, New Zealand

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Title: Dusky dolphin (Lagenorhynchus obscurus) occurrence and movement patterns near Kaikoura, New Zealand
Author: Dahood, Adrian D.
Abstract: In Kaikoura , New Zealand dusky dolphins (Lagenorhynchus obscurus ) are economically and ecologically important . However , more information on key habitat requirements is needed to develop an effective management plan for them . I use systematic shore -based observations and tour operator gathered boat -based observations and review night -time foraging observations to explore dusky dolphin occurrence and movement patterns . I discuss possible influence of prey on these patterns . From January to December 2006 , I conducted crepuscular observations from three clifftop stations . With these geospatial data I examined occurrence , mean speed , and linearity over seasonal , diel , and tidal temporal scales . From October 1995 to November 2006 tour guides recorded GPS locations for over 5 ,000 dusky dolphin groups , allowing me to examine seasonal occurrence patterns . For both datasets I quantified occurrence patterns relative to depth , distance from the Kaikoura Canyon , and distance from shore . I reviewed the three studies conducted on dusky night foraging behavior in Kaikoura . I explore the effects of seasonal and lunar -scale changes in night -time light levels on dusky dolphin foraging behavior . Duskies exhibited seasonal and diel , but not tidal occurrence and movement patterns . Dolphins were found farther offshore , in deeper water , and travelling faster in winter and approaching sunset . The areas of highest sightings density were associated with the Kaikoura Canyon , and shifted almost entirely into the canyon in winter and approaching sunset . Dolphins made sharper turns during summer . Dolphins were , on average , closer to the Kaikoura Canyon than to shore . Seasonal occurrence patterns described by tour operator data agreed with those described by geospatial data collected by shorebased observers . Duskies exhibited flexible foraging behavior and appeared to use both seasonal and lunar phase specific tactics . Night -time light levels appeared to influence dusky foraging behavior , possibly through changes in prey behavior . Prey availability and behavior patterns appeared to influence dusky occurrence and movement patterns . The dolphins' affinity for the Kaikoura Canyon may reflect a strategy to maximize access to prey .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2009 -05 -452
Date: 2010-01-16

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Dusky dolphin (Lagenorhynchus obscurus) occurrence and movement patterns near Kaikoura, New Zealand. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2009 -05 -452 .

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