[MARMAM] Publication on inferring causal factors for declining dolphin populations
rohan.currey at gmail.com
Thu Sep 30 00:21:47 PDT 2010
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.
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.
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