Surprise Encounters With Humpback Whales

Project Name:

Surprise Encounters With Humpback Whales

Study System:

North Pacific humpback whale (Megaptera novaeangliae) – Endangered

Motivation and Goals:

Since whale and vessel numbers are on the rise within HIHWNMS, we are studying which factors affect the likelihood of collisions between vessels and whales.  This information will help guide vessel speed restrictions and provide mitigation measures for reducing whale-vessel collisions.

Methods:

Encounters with humpback whales are recorded as “Surprise Encounters” if the whale is first detected within 300 yards of the vessel or “Near Misses” if the whale is first detected within 80 yards of the vessel.  Surprise encounters and near misses are used as proxies for collisions. 

To test how vessel speed and environmental conditions affect the likelihood of a collision, we use line transects to survey Maui waters at different speeds and in different weather conditions while searching for humpback whales. 

To test whether particular age groups or certain individuals might be more susceptible to collisions, we also take identification photos and record data on pod composition and behavior.

Previous phases of this project also involved a researcher placed on board PWF eco-tour vessels to record surprise encounters and near misses.  Currently, however, all data are collected from Ocean Protector. 

Results to Date: 

Speed is the most important factor affecting the probability of detecting a whale, with increasing vessel speed resulting in decreased likelihood of detection, particularly speeds above 12.5 knots.  

Douglas Sea State (swell) also affects whale detection, resulting in more surprise encounters and near misses with increasing sea state.  

Next Steps:

This study has one final year (2015 – 2016 season).  In the final season we are adding land-based observation to assess the behavior of humpback whales before, during, and after vessels pass. 

Most Recent Publication: 

2015. Currie, J.J., Stack, S.H., Easterly, S.K., Kaufman, G.D., Martinez, E. Modeling whale-vessel encounters: the role of speed in mitigating collisions with humpback whales (Megaptera novaeangliae). Document SC/66a/HIM/03 presented to the IWC Scientific Committee, San Diego, USA: 20 May – 4 June. 17 pp.