Blue Whale Body Condition Assessed Over a 14-Year Period in the NE Pacific: Annual Variation and Connection to Measures of Ocean Productivity

Wachtendonk, Rachel; Calambokidis, John; Flynn, Kiirsten

doi:10.3389/fmars.2022.847032

Cited by 8 publications

(3 citation statements)

References 53 publications

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“…While inhabiting the CalCOFI region they forage exclusively on krill, preferring Thysanoessa spinifera to North Pacific krill (Nickels et al, 2019). Due to their specialized foraging preferences, blue whale encounter rates may be an indicator of local productivity (Wachtendonk et al, 2022). In the summer of 2021, encounter rates of blue whales were the highest throughout the timeseries (Supplementary Appendix).…”

Section: At Sea Birds and Mammalsmentioning

confidence: 99%

State of the California Current Ecosystem report in 2022: a tale of two La Niñas

Thompson,

Swalethorp,

Alksne

et al. 2024

Front. Mar. Sci.

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2022 marked the third consecutive La Niña and extended the longest consecutive stretch of negative Oceanic Niño Index since 1998-2001. While physical and biological conditions in winter and spring largely adhered to prior La Niña conditions, summer and fall were very different. Similar to past La Niña events, in winter and spring coastal upwelling was either average or above average, temperature average or below average, salinity generally above average. In summer and fall, however, upwelling and temperature were generally average or slightly below average, salinity was close to average and chlorophyll a was close to average. Again, as during prior La Niña events, biomass of northern/southern copepods was above/below average off Oregon in winter, and body size of North Pacific krill in northern California was above average in winter. By contrast, later in the year the abundance of northern krill dropped off Oregon while southern copepods increased and body sizes of North Pacific krill fell in northern California. Off Oregon and Washington abundances of market squid and Pacific pompano (indicators of warm, non-typical La Niña conditions) were high. In the 20th century, Northern anchovy recruitment tended to be high during cold conditions, but despite mostly warm conditions from 2015-2021 anchovy populations boomed and remained high in 2022. Resident seabird reproductive success, which tended in the past to increase during productive La Niña conditions was highly variable throughout the system as common murre and pelagic cormorant, experienced complete reproductive failure at Yaquina Head, Oregon while Brandt’s cormorant reproduction was average. At three sampling locations off central California, however, common murre reproduction was close to or above average while both pelagic and Brandt’s cormorant were above average. California sealion reproduction has been above average each year since 2016, and pup weight was also above average in 2022, likely in response not to La Niña or El Niño but continuous high abundance of anchovy. The highly variable and often unpredictable physical and biological conditions in 2022 highlight a growing recognition of disconnects between basin-scale indices and local conditions in the CCE. “July-December 2022 is the biggest outlier from individual “strong” La Niña (events) ever going back to the 50s.” – Nate Mantua

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Section: At Sea Birds and Mammalsmentioning

confidence: 99%

State of the California Current Ecosystem report in 2022: a tale of two La Niñas

Thompson,

Swalethorp,

Alksne

et al. 2024

Front. Mar. Sci.

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“…There may be several reasons as to why there is a difference in BC between the west and east coast populations, including temporal variation. Baleen whales showed fluctuations in BC among years of varying environmental conditions (Lockyer 1986;Vikingsson et al 2013;Soledade Lemos et al 2020;Wachtendonk et al 2022), with the potential for this change to be extreme (Coughran et al 2023). This may lead to different amounts of acquired energy among different feeding seasons and, in turn, a poorer or better BC at the time of sampling.…”

Section: Body Condition Comparison Between West and East Coast Popula...mentioning

confidence: 99%

Comparisons of morphometrics and body condition between two breeding populations of Australian humpback whales

Russell,

Christiansen,

Colefax

et al. 2023

Wildlife Res.

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Context The east and west coasts of Australia form the breeding grounds for two of the world’s largest and fastest-growing populations of humpback whales (Megaptera novaeangliae). These populations show differences in mean lipid content, fatty acid profiles, and stable isotope values. Aims To determine whether these differences result in variation in nutritional health and physiology between populations, we quantified and compared the morphology, body condition and energetic requirements between the two populations. Methods We used unmanned aerial vehicles to measure body morphometrics (residual of body volume vs length) of humpback whales from May to November in 2017, 2020 and 2021. Key results Morphometric measurements were obtained from 973 humpback whales (119 calves, 249 juveniles, 486 adults, and 119 lactating females). Results showed that the two populations did not differ significantly in their morphology. The average body condition was significantly different for sexually mature reproductive classes, with adults and lactating females on the west coast having a lower body condition, by an average of 7.7 and 11.1 percentage points below the east coast population respectively. All reproductive classes, with the exception of calves followed a similar pattern in body condition loss through the breeding season. Calves on the east coast exhibited a curvilinear relationship with days post-partum, with early and late-migrating calves being in poorer body condition than were those migrating mid-season. In contrast, west coast calves did not significantly change their condition through the breeding season. Conclusions The poorer body condition of sexually mature individuals in the west coast population is concerning, given the overall condition loss during a breeding season. This difference could be influenced by variations in sampling time; however, differences in feeding opportunities, climatic regimes and/or environmental variables may influence the ability of one population to acquire similar amounts of energy. Implications The difference in body condition between these two humpback whale populations highlighted the need to assess populations individually, so as to develop representative levels that can be used for future conservation monitoring and management.

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“…In contrast to strict capital breeders that may fast for months on the wintering/breeding grounds (i.e., southern right whales, Eubalaena australis, Carroll et al, 2021), blue whales likely fast for short periods of time while transiting between summer and winter foraging grounds (Bailey et al, 2009). This strategy makes blue whales particularly vulnerable to changes in resource availability because of their high energetic requirements (Acevedo-Gutieŕrez et al, 2002), and whales in poor body condition are frequently observed during years characterized by low primary productivity (Casillas-López, 2016;Wachtendonk et al, 2022). Studies that address individual migratory and dietary strategies of this species are needed to better understand habitat use, and how this varies among age and sex categories, which in turn would provide information on population dynamics that are critical to their management and conservation.…”

Section: Introductionmentioning

confidence: 99%

Sex- and age-specific migratory strategies of blue whales in the northeast Pacific Ocean

et al. 2022

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Migration is a complex behavior that has evolved in multiple taxonomic groups as a means of accessing productive foraging grounds and environmentally stable areas suitable for reproduction. For migratory whales that forage throughout the year because of their high energetic demands, changes in the abundance of prey in different areas along their migratory route(s) can have serious implications for individual fitness and population viability. Thus, identifying the regions these species use to forage and breed while evaluating their migratory plasticity at the individual level can provide key information for their management and conservation. Serial stable isotope analysis of whale baleen, a continuously growing but metabolically inert tissue, has proven useful in generating individual migratory and foraging records over several years prior to death. We measured carbon (δ13C) and nitrogen (δ15N) isotope values along the length of baleen plates collected from thirteen blue whales of different sex and age classes, representing the largest collection analyzed to date in the northeast Pacific Ocean. Adult females exhibited relatively stable seasonal movements between temperate latitude foraging grounds and subtropical breeding grounds, although two skipped migration one year and subsequently moved to the same subtropical breeding ground near the Costa Rica Dome, potentially to give birth. Adult males exhibited two movement strategies with most remaining at temperate latitudes for 3-4 years before death, while two migrated to subtropical breeding grounds. In contrast, movement patterns in juveniles were erratic. These results are potentially driven by the energetic requirements during pregnancy and nursing in adult females, intra-specific competition among adult males, and inexperience in locating prey in juveniles. We also describe baleen δ15N patterns in recently weaned whales (<16.5m) that reflect switching from the consumption of milk to solid food (krill). In addition, baleen δ13C data suggest that weaned whales continue to use stored nutrients (blubber) acquired during the nursing period long after they are weaned. These results broaden our understanding of habitat selection in this species, highlight the importance of nursing for the critical period after weaning, and indicate that the Costa Rica Dome is an important calving region for this endangered population.

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Blue Whale Body Condition Assessed Over a 14-Year Period in the NE Pacific: Annual Variation and Connection to Measures of Ocean Productivity

Cited by 8 publications

References 53 publications

State of the California Current Ecosystem report in 2022: a tale of two La Niñas

State of the California Current Ecosystem report in 2022: a tale of two La Niñas

Comparisons of morphometrics and body condition between two breeding populations of Australian humpback whales

Sex- and age-specific migratory strategies of blue whales in the northeast Pacific Ocean

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