[MARMAM] New publication: Population Viability Analysis and Comparison of Two Monitoring Strategies for Bottlenose Dolphins (Tursiops truncatus) in the Shannon Estuary, Ireland, to Inform Management

Miguel Blázquez miguelblazvas5 at gmail.com
Thu May 14 13:22:18 PDT 2020

 Dear colleagues,

We are glad to share our recent publication with you:

Blázquez, M., Baker, I., O'Brien, J. M., & Berrow, S. D. (2020). Population
Viability Analysis and Comparison of Two Monitoring Strategies for
Bottlenose Dolphins (Tursiops truncatus) in the Shannon Estuary, Ireland,
to Inform Management. Aquatic Mammals, 46(3), 307-325, DOI

Photo-identification has been used to monitor the resident bottlenose
dolphin (Tursiops truncatus) population in the Lower River Shannon Special
Area of Conservation in Ireland as part of European Union obligations since
1997. A discovery curve using data collected by the Irish Whale and Dolphin
Group (IWDG) between 2011 and 2015 suggested all animals in the population
were captured during this period, providing an abundance of 145 extant
individuals. The IWDG photo-identification catalogue was compared with an
independently derived photo-identification catalogue compiled by the
National Parks and Wildlife Service during 2015 to identify whether any
individuals were not captured by the IWDG during that year; there were
none. Mark-recapture analysis of both photo-identification catalogues
indicated that the higher survey effort provided a higher and more precise
abundance estimate, and the estimate of 145 individuals in the population
was supported. Population Viability Analysis using this most up-to-date
abundance estimate and new data on life-history characteristics were used
to explore population status under a range of potential scenarios. A
baseline model showed slowly declining dynamics with a growth rate (r) of
-0.007. An increase in adult mortality from 3.8 to 7.0% (e.g., due to
bycatch) led to a steep decline in population size. Similar results were
obtained when the effects of an infrequent catastrophic event (e.g., a
large oil spill) were simulated. Sensitivity analysis revealed the
importance of female reproductive capacity for population viability. These
results will help local managers to understand the implications of events
that may affect this small, genetically discrete resident population. The
current monitoring strategy may be insufficient to obtain a thorough
understanding of population dynamics; hence, higher survey effort is
recommended to gain a better knowledge of key demographic parameters which
may affect population viability, especially those limiting female
reproductive capacity.



Feel free to contact us.

Best and stay safe.

Miguel Blázquez.
Irish Whale and Dolphin Group
Merchants Quay, Kilrush, County Clare, Ireland.
Email: miguelblazvas5 at gmail.com
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