This project aims to develop a method to rapidly assess delphinid population age structure. This will ultimately provide an assessment of population growth and survival rates, and early insight into whether there may be cause for concern for specific populations.

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Background Information


The power to detect population increases or declines using traditional photo-identification methods typically requires decades of data collection before changes in vital rates (e.g. survival, fertility etc.) manifest themselves as changes in population size. New technologies are available that enable assessment of group composition and population age structure, as well as measures of individual animal health that can ultimately provide assessment of population growth and survival rates, and early insight into whether there may be cause for concern for these populations. This project consists of a two-phase study to assess the feasibility of using small Unoccupied Aerial Vehicles (UAVs, or drones) to determine the population age structure of mid-sized delphinids. For this project, we will focus on the Hawaiian population of spinner dolphins, off the Kona coastline (Hawaii).




The long-term objective of this project is to define the age structuration of the spinner dolphin population off the Kona coastline (Hawaii) to provide a means by which to assess this population trajectory and health status. This project will be achieved via two phases.


The aims of the first phase of this project are to:

  • Collect both UAV aerial images of dolphins at a public facility (Dolphin Quest, Oahu), and actual hands-on measurements of dolphin length and girth.

  • Calibrate and test the precision of UAV-obtained length measurements of dolphins at a public facility by comparing UAV-derived length estimates with hands-on measurements of the dolphins.

​The aims of the second phase of this project are to (see figure 1):

  • Estimate the length of free-ranging spinner dolphins off the Kona Coast off the Island of Hawaii.

We will collect vertical photogrammetry (making measurements from photographs) images of spinner dolphins via multi-rotor UAVs (drones), off the Kona Coast of Hawaii Island. We will operate the UAV over groups of spinner dolphins within and outside of their four main resting bays (Makako Bay, Kealakekua Bay, Honaunau Bay and Kauhako Bay, Hawaii Island).


  • Develop age-length growth curves for Hawaiian spinner dolphins

In order to utilize photogrammetric methods to assign animals to age classes, it is important to have auxiliary information, i.e. length-at-age growth curves. Growth curves will be informed for Hawaiian spinner dolphins from two data sources: a) published literature on by-caught eastern spinner dolphins from the Eastern Tropical Pacific tuna fishery and b) available stranding specimens of Hawaiian spinner dolphins (n=30).


Figure 1. Schematic overview of the study components to assess the feasibility of using multi- rotor unoccupied aerial vehicles to determine delphinid group age composition and population age-structure.

research team

Lars Bejder - MMRP

Fabien Vivier - MMRP

Cormac Booth - SMRU Consulting

Erin Oleson - NOAA/PIFSC

Amanda Bradford - NOAA/PIFSC

Marie Hill - NOAA/JIMAR


Kristi West - Stranding network/MMRP

Jason Baker - NOAA

Aude Pacini - MMRP

Julie Rocho-Levine - DQ



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      Hawaii Institute of Marine Biology

      46-007 Lilipuna Road

      KANEOHE, HI 96744



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