[MARMAM] PhD Thesis on the Fiordland Bottlenose Dolphins

Rohan Currey rohan.currey at gmail.com
Tue Jan 12 00:04:59 PST 2010


Dear colleagues,

The following thesis was recently published online:

Currey, R.J.C. 2008. Conservation biology of bottlenose dolphins in  
Fiordland, New Zealand. PhD Thesis, University of Otago, Dunedin, New  
Zealand.

The bottlenose dolphins of Fiordland, New Zealand, live at the  
southern limit of the species’ worldwide range. They are exposed to  
impacts from tourism and habitat modification, particularly in  
Doubtful Sound, and their conservation requirements are presently  
unclear. Dolphin abundance was estimated in Doubtful Sound using  
photoidentification census and capture-recapture techniques (56  
individuals; 95% CI: 55-57), detecting a decline of 34-39% over 12  
years among adults and sub-adults (>3 years old). The cause of this  
decline was investigated via demographic modelling in Doubtful Sound  
and a comparative assessment of population status in Dusky Sound.  
Capture-recapture modelling of photo-identification data compiled  
since 1990 yielded a constant adult survival rate marginally lower  
than prior estimates for wild bottlenose dolphins (φa(1990–2008) =  
0.9374; 95% CI: 0.9170-0.9530). Survival of calves (<1 year old)  
declined to an unsustainable level that is thought to be the lowest  
recorded for wild bottlenose dolphins (φc(2002–2008) = 0.3750; 95%  
CI: 0.2080-0.5782) coincident with the opening of a second tailrace  
tunnel for a hydroelectric power station. Reverse-time capture- 
recapture modelling detected declines in recruitment (f(1994–2008) =  
0.0249; 95% CI: 0.0174-0.0324) and population growth (λ(1994–2008)  
= 0.9650; 95% CI: 0.9554-0.9746) over time consistent with the  
decline in calf survival (<1 year old) and a separate reduction in  
juvenile survival (1 to 3 years old) reflecting cumulative impacts.  
Dolphin abundance was estimated in Dusky Sound using photo- 
identification census and capture-recapture techniques (102  
individuals; 95% CI: 100-104) providing no evidence of interchange  
with Doubtful Sound. A comparative assessment of health status  
between Doubtful and Dusky Sounds revealed skin lesioning was more  
severe in Doubtful Sound, particularly among females, and newborn  
calves appeared to be smaller and were born over a shorter period:  
factors that may contribute to the low levels of calf survival in  
Doubtful Sound. The Fiordland bottlenose dolphins were assessed under  
IUCN Red List regional criteria. The small size of the population  
(205 individuals; 95% CI: 192-219) combined with the projected rate  
of decline in stochastic matrix models (average decline: 31.4% over  
one generation) resulted in a recommended classification of  
Critically Endangered.

A PDF copy of the thesis is available at:
http://hdl.handle.net/10523/129

Best wishes,

Dr Rohan Currey



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