‘Whale wave’: shifting strategies structure the complex use of critical fjord habitat by humpbacks

Keen, Eric M.; Wray, Janie; Meuter, Hermann; Thompson, Kim-Ly; Barlow, Jay; Picard, Chris R.

doi:10.3354/meps12012

Cited by 15 publications

(24 citation statements)

References 54 publications

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“…Whale distribution also became more dispersed and trended further inland (measured as distance from the fjord source; see Keen et al. ).…”

Section: Resultsmentioning

confidence: 98%

“…Acoustic backscatter processing is detailed in Keen et al. (). In summary, the Syqwest Hydrobox outputs a pixelated representation of water column backscatter.…”

Section: Methodsmentioning

confidence: 99%

“…Deepwater krill imaging and zooplankton tows were used to verify the efficacy of 200 kHz backscatter processing methods (Keen et al. ).…”

Section: Methodsmentioning

confidence: 99%

“…The study area was split into 26 strata (after Keen et al. ), such that there were 26 data points for each of seven surveys (two in 2014 and five in 2015; n = 159). “Prey conditions” were represented using acoustic backscatter metrics and physiographic variables that may influence prey aggregation (seafloor depth and slope and evidence of tidal fronts).…”

Section: Methodsmentioning

confidence: 99%

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Aggregative and feeding thresholds of sympatric rorqual whales within a fjord system

Keen

2017

Ecosphere

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Citation: Keen, E. M. 2017. Aggregative and feeding thresholds of sympatric rorqual whales within a fjord system. Ecosphere 8(3):e01702. 10. 1002/ecs2.1702 Abstract. Rorqual whales (f. Balaenopteridae) supposedly respond to increases in prey supply according to both aggregative and feeding thresholds. With the former, they gather in areas above a minimum prey density set by their basal metabolic needs. With the latter, feeding occurs only above a prey density set by the energetic cost of lunge feeding. To compare prey preferences and the two threshold types in sympatric rorquals, I conducted systematic transect surveys and behavioral observations of humpback whales (Megaptera novaeangliae) and fin whales (Balaenoptera physalus) in a British Columbia fjord system. While multiple prey features were found to influence whale aggregation and feeding, both threshold types were observed in each species' response to krill volume. Humpback response to prey features was less predictable and influenced by more factors than that of fin whales, which appeared to be exclusively euphausivorous and interested in the deepest high-volume krill patches within the deepest channels. Compared with fin whales, humpbacks found higher-volume krill patches and had higher aggregative thresholds, but had lower feeding thresholds. Findings aligned overall with the expectations that aggregative behavior is responsive to local prey supply, while feeding thresholds are governed by less mutable energetic constraints imposed by body size and feeding mode. Both aggregative and feeding threshold responses appeared to be a function of local conditions: As total krill-like backscatter increased, feeding thresholds stabilized (became more nonlinear and more nonrandom), while aggregative thresholds destabilized. All results emphasized the importance of incorporating observations of feeding effort in studies of prey preference and habitat use.

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“…Whale distribution also became more dispersed and trended further inland (measured as distance from the fjord source; see Keen et al. ).…”

Section: Resultsmentioning

confidence: 98%

“…Acoustic backscatter processing is detailed in Keen et al. (). In summary, the Syqwest Hydrobox outputs a pixelated representation of water column backscatter.…”

Section: Methodsmentioning

confidence: 99%

“…Deepwater krill imaging and zooplankton tows were used to verify the efficacy of 200 kHz backscatter processing methods (Keen et al. ).…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Aggregative and feeding thresholds of sympatric rorqual whales within a fjord system

Keen

2017

Ecosphere

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“…The Kitimat Fjord System, adjacent to our study region, has been identified as a region frequented by rorqual whales (Keen , Keen et al. ). Similarly, our GAMs show elevated densities of HWs and MWs in Caamano Sound, next to the Kitimat Fjord.…”

Section: Discussionmentioning

confidence: 97%

Quantifying marine mammal hotspots in British Columbia, Canada

et al. 2017

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Abstract. Global biodiversity is undergoing rapid decline due to direct and indirect anthropogenic impacts to species and ecosystems. Marine species, in particular, are experiencing accelerated population declines leading to many species being considered at risk by regional, national, and international standards. As one conservation approach, decisions made using spatially explicit information on marine wildlife populations have the potential to facilitate recovery and contribute to national and international commitments toward conservation targets. Delineating areas of intense use by species at risk can inform future marine spatial planning and conservation efforts, including the identification of marine protected areas. Methods for detecting hotspots (e.g., areas with high density and/or abundance) enable categorical mapping of the most intensely used areas. Yet, many of the current methods for delineating hotspots, such as the top 5% threshold, are subjective and fail to account for spatial patterns. Our goal was to map spatially continuous distributions of marine mammal densities and employ quantitative statistical methods to extract hotspot locations on the northern coast of British Columbia. We integrated systematically surveyed species information with environmental variables using generalized additive models to predict marine mammal distribution and density. Hotspots were identified from the density surfaces using two approaches: aspatial top 5% method and spatially local G i Ã statistic using three neighborhood definitions.Heterogeneous density patterns were observed for all species, and high-density regions were generally clustered in areas exhibiting oceanographic characteristics that may promote concentrated food resources. Combining species density surfaces and extracting hotspot locations identified regions important to multiple species and present candidate locations for future conservation efforts. Contributions from this research provide robust statistical methods to objectively map hotspot locations and generate GIS data products for informing coastal conservation decisions.

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Indigenous food harvesting as social–ecological monitoring: A case study with the Gitga'at First Nation

Thompson

Hill²,

Ojeda

et al. 2020

People and Nature

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‘Whale wave’: shifting strategies structure the complex use of critical fjord habitat by humpbacks

Cited by 15 publications

References 54 publications

Aggregative and feeding thresholds of sympatric rorqual whales within a fjord system

Aggregative and feeding thresholds of sympatric rorqual whales within a fjord system

Quantifying marine mammal hotspots in British Columbia, Canada

Indigenous food harvesting as social–ecological monitoring: A case study with the Gitga'at First Nation

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