[MARMAM] Publication on inferring causal factors for declining dolphin populations

Rohan Currey rohan.currey at gmail.com
Thu Sep 30 00:21:47 PDT 2010

Dear colleagues,

The following article was recently published online:

Currey, R. J. C., Dawson, S. M., Schneider, K., Lusseau, D.,  
Boisseau, O. J., Haase, P. A., & Slooten, E. 2010. Inferring causal  
factors for a declining population of bottlenose dolphins via  
temporal symmetry capture-recapture modelling. Marine Mammal Science.  
doi: 10.1111/j.1748-7692.2010.00417.x

We applied temporal symmetry capture–recapture (TSCR) models to  
assess the strength of evidence for factors potentially responsible  
for population decline in bottlenose dolphins (Tursiops truncatus) in  
Doubtful Sound, New Zealand from 1995 to 2008. Model selection was  
conducted to estimate recruitment and population growth rates. There  
were similar levels of support for three different models, each  
reflecting distinct trends in recruitment. Modeling yielded low  
overall estimates of recruitment (0.0249, 95% CI: 0.0174–0.0324) and  
population growth rate (0.9642, 95% CI: 0.9546–0.9737). The TSCR rate  
of population decline was consistent with an estimate derived from  
trends in abundance (lambda = 0.9632, 95% CI: 0.9599–0.9665). The  
TSCR model selection confirmed the influence of a decline in the  
survival of calves (<1 yr old) since 2002 for population trends.  
However, TSCR population growth rates did not exceed 1 in any year  
between 1995 and 2008, indicating the population was declining prior  
to 2002. A separate reduction in juvenile survival (1–3 yr old) prior  
to 2002 was identified as a likely contributing factor in the  
population decline. Thus, TSCR modeling indicated the potential cause  
of the population decline in Doubtful Sound: cumulative impacts on  
individuals <3 yr old resulting in a reduced recruitment.

A PDF copy of the article is available at:

Alternatively, please send requests to rohan.currey at gmail.com.

Best wishes,

Rohan Currey
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