Diel differences in blue whale (Balaenoptera musculus) dive behavior increase nighttime risk of ship strikes in northern Chilean Patagonia

• Published in: Integrative Zoology
• Main Authors: Caruso, Francesco, Hickmott, Leigh, Warren, Joseph D., Segre, Paolo, Chiang, Gustavo, Bahamonde, Paulina, Español-Jiménez, Sonia, Li, Songhai, Bocconcelli, Alessandro
• Other Authors: University of St Andrews. School of Biology, University of St Andrews. Sea Mammal Research Unit
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Bio-logging tags; Blue whale; Diving profile; Ocean conservation; Prey distribution; QH301 Biology; DAS; SDG 14 - Life Below Water; QH301; East Ridge; Indian; Patagonia; Balaenoptera musculus
• Online Access: http://hdl.handle.net/10023/21115; https://doi.org/10.1111/1749-4877.12501

The data analysis and paper writing was financially supported by the National Key Research and Development Program of China (Grant number 2016YFC0300802); the biodiversity investigation, observation and assessment program (2019‐2023) of the Ministry of Ecology and Environment of China; and Indian Ocean Ninety‐east Ridge Ecosystem and Marine Environment Monitoring and Protection, supported by the China Ocean Mineral Resources R&D Association (no. DY135‐E2‐4). Additionally, FC thanks the President's International Fellowship Initiative (PIFI) of the Chinese Academy of Sciences. The northern Chilean Patagonia region is a key feeding ground and a nursing habitat in the southern hemisphere for blue whales (Balaenoptera musculus). From 2014 to 2019, during 6 separate research cruises, the dive behavior of 28 individual blue whales was investigated using bio‐logging tags (DTAGs), generating ≈190 h of data. Whales dove to significantly greater depths during the day compared to nighttime (day: 32.6 ± 18.7 m; night: 6.2 ± 2.7 m; P < 0.01). During the night, most time was spent close to the surface (86% ± 9.4%; P < 0.01) and at depths of less than 12 m. From 2016 to 2019, active acoustics (scientific echosounders) were used to record prey (euphausiids) density and distribution simultaneously with whale diving data. Tagged whales appeared to perform dives relative to the vertical migration of prey during the day. The association between diurnal prey migration and shallow nighttime dive behavior suggests that blue whales are at increased risk of ship collisions during periods of darkness since the estimated maximum ship draft of vessels operating in the region is also ≈12 m. In recent decades, northern Chilean Patagonia has seen a large increase in marine traffic due to a boom in salmon aquaculture and the passenger ship industry. Vessel strike risks for large whales are likely underestimated in this region. Results reported in this study may be valuable for policy and mitigation decisions regarding conservation ...