[MARMAM] New publication - Fluctuating reproductive rates in Hawaii's humpback whales

Cartwright, Rachel Rachel.Cartwright at csuci.edu
Tue Mar 26 17:07:36 PDT 2019

Hi Marmam colleagues,

My co-authors and I would like to share with you our recent publication:

Cartwright, R., Venema, A., Hernandez, V., Wyels, C., Cesere, J., & Cesere, D. (2019). Fluctuating reproductive rates in Hawaii's humpback whales, Megaptera novaeangliae, reflect recent climate anomalies in the North Pacific. Royal Society Open Science, 6(3), 181463

Alongside changing ocean temperatures and ocean chemistry, anthropogenic climate change is now impacting the fundamental processes that support marine systems. However, where natural climate aberrations mask or amplify the impacts of anthropogenic climate change, identifying key detrimental changes is challenging. In these situations, long-term, systematic field studies allow the consequences of anthropogenically driven climate change to be distinguished from the expected fluctuations in natural resources. In this study, we describe fluctuations in encounter rates for humpback whales, Megaptera novaeangliae, between 2008 and 2018. Encounter rates were assessed during transect surveys of the Au'Au Channel, Maui, Hawaii. Initially, rates increased, tracking projected growth rates for this population segment. Rates reached a peak in 2013, then declined through 2018. Specifically, between 2013 and 2018, mother–calf encounter rates dropped by 76.5%, suggesting a rapid reduction in the reproductive rate of the newly designated Hawaii Distinct Population Segment of humpback whales during this time. As this decline coincided with changes in the Pacific decadal oscillation, the development of the NE Pacific marine heat wave and the evolution of the 2016 El Niño, this may be another example of the impact of this potent trifecta of climatic events within the North Pacific

The open access paper may be reached via this link: https://royalsocietypublishing.org/doi/10.1098/rsos.181463

Although the changes documented in the study are potentially concerning, there is some good news to report. During the 2019 season, we saw the first signs of recovery from this decline, as sighting rates for mother-calf pairs in Maui waters rose slightly. Here’s hoping this trend continues.

 With best regards,
Rachel Cartwright

Lead researcher – Keiki Kohola Project.
Email: rachel.cartwright at csuci.edu
Website: www.caringforcalves.org

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