[MARMAM] NEW PUBLICATION: Quantifying the age structure of free-ranging delphinid populations: Testing the accuracy of Unoccupied Aerial System photogrammetry

Fabien Vivier fvivier at hawaii.edu
Wed Jun 28 16:33:50 PDT 2023

Dear MARMAM community,

My co-authors and I are pleased to share with you our new paper entitled
"Quantifying the age structure of free-ranging delphinid populations:
Testing the accuracy of Unoccupied Aerial System photogrammetry", published
in *Ecology and Evolution*.

The paper can be accessed and downloaded here:


Understanding the population health status of long-lived and
slow-reproducing species is critical for their management. However, it can
take decades with traditional monitoring techniques to detect
population-level changes in demographic parameters. Early detection of the
effects of environmental and anthropogenic stressors on vital rates would
aid in forecasting changes in population dynamics and therefore inform
management efforts. Changes in vital rates strongly correlate with
deviations in population growth, highlighting the need for novel approaches
that can provide early warning signs of population decline (e.g., changes
in age structure). We tested a novel and frequentist approach, using
Unoccupied Aerial System (UAS) photogrammetry, to assess the population age
structure of small delphinids. First, we measured the precision and
accuracy of UAS photogrammetry in estimating total body length (TL) of
trained bottlenose dolphins (Tursiops truncatus). Using a log-transformed
linear model, we estimated TL using the blowhole to dorsal fin distance
(BHDF) for surfacing animals. To test the performance of UAS photogrammetry
to age-classify individuals, we then used length measurements from a
35-year dataset from a free-ranging bottlenose dolphin community to
simulate UAS estimates of BHDF and TL. We tested five age classifiers and
determined where young individuals (<10 years) were assigned when
misclassified. Finally, we tested whether UAS-simulated BHDF only or the
associated TL estimates provided better classifications. TL of surfacing
dolphins was overestimated by 3.3% ±3.1% based on UAS-estimated BHDF. Our
age classifiers performed best in predicting age-class when using broader
and fewer (two and three) age-class bins with ~80% and ~72% assignment
performance, respectively. Overall, 72.5%–93% of the individuals were
correctly classified within 2 years of their actual age-class bin. Similar
classification performances were obtained using both proxies. UAS
photogrammetry is a non-invasive, inexpensive, and effective method to
estimate TL and age-class of free-swimming dolphins. UAS photogrammetry can
facilitate the detection of early signs of population changes, which can
provide important insights for timely management decisions.

How to cite this paper:

Vivier, F., Wells, R. S., Hill, M. C., Yano, K. M., Bradford, A. L.,
Leunissen, E. M., Pacini, A., Booth, C. G., Rocho-Levine, J., Currie, J.
J., Patton, P. T., & Bejder, L. (2023). Quantifying the age structure of
free-ranging delphinid populations: Testing the accuracy of Unoccupied
Aerial System photogrammetry. Ecology and Evolution, 13, e10082.

Feel free to reach out if you have any questions or problems accessing the
link (fvivier at hawaii.edu).

Finally, we would like to thank our funders and research partners:
NOAA-PIFSC, Cooperative Institute for Marine and Atmospheric Research,
Office of Naval Research and Dolphin Quest.


Fabien Vivier
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.uvic.ca/pipermail/marmam/attachments/20230628/65bfeaa4/attachment.html>

More information about the MARMAM mailing list