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Papers by Jan Straley

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Sperm whales (Physeter macrocephalus) remove fish from longline fishing gear. This behavior is ca... more Sperm whales (Physeter macrocephalus) remove fish from longline fishing gear. This behavior is calle…

The long-term goal of this work is to develop techniques for tracking marine mammal sounds in ran... more The long-term goal of this work is to develop techniques for tracking marine mammal sounds in range and depth from a single mooring or platform (e.g. glider), by exploiting the propagation effects of the deep-water sound speed channel. Most listening platforms currently use a single hydrophone to detect events, making no effort at localization. For beaked whales (which have a limited detection range of about 5-7 km), detection may be sufficient to determine whether an animal is close to potential naval operations, but for most species, one needs to assume a typical source level (or source level distribution) to translate a detection's received level into a distance, a risky assumption that generates large uncertainties in position, which in turn degrades attempts at acoustic density estimation and makes mitigation decisions problematic.

Marine Ecology Progress Series, Dec 15, 2016

Humpback whales Megaptera novaeangliae are filter feeders that use discrete lunges to effectively... more Humpback whales Megaptera novaeangliae are filter feeders that use discrete lunges to effectively capture densely aggregated prey. The objective of this research was to examine how foraging humpback whales in Southeast Alaska responded to varying prey patch densities and depths. Digital acoustic recording tags (DTAGs; n = 6) were deployed and focal follows were conducted on foraging whales in Sitka Sound, Alaska in September 2012. Prey density was recorded around tagged whales using a Simrad EK60 scientific echosounder and ground-truthed with net tows. Lunges were identified from peaks in jerk in the accelerometer signal, and krill were identified from echosounder data using decibel differencing. Lunge depth was 111 ± 9 m (mean ± SD) for the shallowest diving whale (foraging past sunset) and 144 ± 7 (mean ± SD) m for the deepest diving whale (foraging diurnally). Ninety-five percent of lunges occurred within a 300 m and 30 min spatio-temporal buffer of krill, indicating that tagged whales fed on krill. Generalized additive mixed model (GAMM) results for spatio-temporally integrated prey and lunge data indicated that mean volume backscattering strength, a proxy for krill density, and krill depth significantly affected the occurrence of a lunge (density: p = 0.006, depth: p < 0.001). Whales fed in the densest region of the krill layer, where mean volume backscatter was −57 dB (range: −50 to −81 dB re 1 m −1 at 120 kHz). By targeting the densest prey layer, whales maximized their energetic gain by capturing the most prey with each lunge.

We present an ocean-basin-scale dataset that includes tail fluke photographic identification (pho... more We present an ocean-basin-scale dataset that includes tail fluke photographic identification (photo-ID) and encounter data for most living individual humpback whales (Megaptera novaeangliae) in the North Pacific Ocean. The dataset was built through a broad collaboration combining 39 separate curated photo-ID catalogs, supplemented with community science data. Data from throughout the North Pacific were aggregated into 13 regions, including six breeding regions, six feeding regions, and one migratory corridor. All images were compared with minimal pre-processing using a recently developed machine learning artificial intelligence image recognition algorithm capable of rapidly detecting matches between individuals to an estimated 97–99% accuracy. For the study period of 2001 to 2021, a total of 27,956 unique individuals were documented in 157,350 encounters. Each individual was encountered, on average, in 5.6 sampling periods (i.e., breeding and feeding seasons), with an annual average...

We present an ocean-basin-scale dataset that includes tail fluke photographic identification (pho... more We present an ocean-basin-scale dataset that includes tail fluke photographic identification (photo-ID) and encounter data for the majority of living individual humpback whales (Megaptera novaeangliae) in the North Pacific Ocean. The dataset was built through a broad collaboration combining 39 separate curated photo-ID catalogs supplemented with community science data. All available images were compared using a recently developed machine learning artificial intelligence image recognition algorithm able to rapidly and accurately detect matches between individuals. For the study period of 2001 to 2021, a total of 27,956 unique individuals were documented in 157,379 encounters, with each individual encountered, on average, in 5.6 sampling periods (i.e., breeding and feeding seasons), and with an annual average of 87.1% of whales encountered in more than one season. The combined dataset and image recognition tool represents a living and accessible resource for collaborative, basin-wide ...

The American Naturalist, 2022

The distributions of marine ectotherms are governed by physiological sensitivities to long-term t... more The distributions of marine ectotherms are governed by physiological sensitivities to long-term trends in seawater temperature and dissolved oxygen. Short-term variability in these parameters has the potential to facilitate rapid range expansions, and the resulting ecological and socioeconomic consequences may portend those of future marine communities. Here, we combine physiological experiments with ecological and demographic surveys to assess the causes and consequences of sudden but temporary poleward range expansions of a marine ectotherm with considerable life history plasticity (California market squid, Doryteuthis opalescens). We show that sequential factors related to resource accessibility in the core range—the buildup of large populations as a result of competitive release and climate-associated temperature increase and oxygen loss that constrain aerobic activity—may drive these expansions. We also reveal that poleward range expansion alters the body size—and therefore trophic role—of invading populations, with potential negative implications for socioeconomically valuable resident species. To help forecast rapid range expansions of marine ectotherms, we advocate that research efforts focus on factors impacting resource accessibility in core ranges. Determining how environmental conditions in receiving ecosystems affect body size and how body size is related to trophic role will help refine estimates of the impacts of future marine communities.

Animals, 2022

Stranded large whales represent an opportunity to learn about the anatomy and health of these cry... more Stranded large whales represent an opportunity to learn about the anatomy and health of these cryptic free-ranging animals. However, where time and access is frequently limited, law enforcement and management priorities often take precedence over research, outreach, and educational uses. On 14 March 2021, a dead female adult humpback whale was reported stranded on an uninhabited island 15 miles west of Sitka, Alaska. The whale was three-dimensionally scanned using light detection and ranging (LiDAR) and photogrammetry before, during, and at multiple time points after a necropsy, including full decomposition 17 days later (NOAA Fisheries permit 18786-01). These scans were organized and displayed on the site Sketchfab with annotations and made publically available as a “4D virtual necropsy” (the fourth dimension is time). After one month, our user survey indicated widespread interest in the platform by both the local community and worldwide by stranding professionals, researchers, and...

: To promote the use of endocrine techniques to advance our knowledge of the physiology of cetace... more : To promote the use of endocrine techniques to advance our knowledge of the physiology of cetaceans and their responses to change in their environment.

Environmental and Ecological Statistics, 2014

In Prince William Sound (PWS), changes in abundance of humpback whales (Megaptera novaeangliae), ... more In Prince William Sound (PWS), changes in abundance of humpback whales (Megaptera novaeangliae), one of PWS's primary marine predator species, have until now been largely unknown. Using a historical dataset (1978-2009), we constructed the first time series of estimated humpback whale abundance in western PWS that is also one of the longest time series used in analyses of humpback whale mark-recapture data.

The Journal of the Acoustical Society of America, 2014

For decades off SE Alaska, sperm whales have located longlining fishing vessels and removed, or “... more For decades off SE Alaska, sperm whales have located longlining fishing vessels and removed, or “depredated,” black cod from the hauls. In 2004, the Southeast Alaska Sperm Whale Avoidance Project (SEASWAP) began deploying passive acoustic recorders on longline fishing gear in order to identify acoustic cues that may alert whales to fishing activity. It was found that when hauling, longlining vessels generate distinctive cavitation sounds, which served to attract whales to the haul site. The combined use of underwater recorders and video cameras also confirmed that sperm whales generated “creak/buzz” sounds while depredating, even under good visual conditions. By deploying recorders with federal sablefish surveys over two years, a high correlation was found between sperm whale creak rate detections and visual evidence for depredation. Thus passive acoustics is now being used as a low-cost, remote sensing method to quantify depredation activity in the presence and absence of various d...

Marine Mammal Science, 2007

Female humpback whales in southeastern Alaska have never been observed with their first calf at a... more Female humpback whales in southeastern Alaska have never been observed with their first calf at ages 5 to 7 years, the documented age at first reproduction in the Gulf of Maine humpback whale population. Long-term sighting histories of 10 individually identified females of known age in southeastern Alaska were used to address this issue. These females were sighted with their first calf at ages 8-16 (mean 11.8) years, significantly older than observed in the Gulf of Maine where 5.91 years is the mean age at first calving. We summarize potential sources of bias and other factors that likely contributed to the difference in age at first calving. Despite their limitations, these are the only available data to assess the age at first calving in North Pacific humpback whales. Figure 1. Stable markings on the ventral tail flukes of humpback whales, like this one photographed in Glacier Bay, Alaska, allow individuals to be identified over many years.

The Journal of the Acoustical Society of America, 2013

Annual federal stock assessment surveys for Alaskan sablefish also attempt to measure sperm whale... more Annual federal stock assessment surveys for Alaskan sablefish also attempt to measure sperm whale depredation by quantifying visual evidence of depredation, including lip remains and damaged fish. An alternate passive acoustic method for quantifying depredation was investigated during the 2011 and 2012 survey hauls. A combination of machine-aided and human analysis counted the number of distinct “creak” sounds detected on autonomous recorders deployed during the survey, emphasizing sounds that are followed by a period of silence (“creak-pauses”), a possible indication of prey capture. These raw counts were then adjusted for variations in background noise levels between deployments. For most locations, the noise-adjusted counts of “creak-pauses” were highly correlated with survey counts of lip remains during both years (2012: r(10) = 0.89, p = 1e-3; 2011: r(39) = 0.72, p = 4e-3) and somewhat correlated with observed sablefish damage in 2011 [r(39) = 0.37, p = 0.03], but uncorrelated ...

Canadian Journal of Zoology, 2004

Despite extensive research on humpback whales (Megaptera novaeangliae (Borowski, 1781)) in parts ... more Despite extensive research on humpback whales (Megaptera novaeangliae (Borowski, 1781)) in parts of the North Pacific, little research has focused on the whales feeding in coastal waters west of Kodiak Island in the Gulf of Alaska. To extend research westward in the North Pacific, small-boat surveys were conducted near the Shumagin Islands during the summers of 1999–2002. Photographs of the natural markings of humpback whales were collected, representing 413 sightings of 171 individual whales. Small samples of skin tissue were collected from 20 individuals, including two mother–calf pairs, for sex identification and comparison of mtDNA haplogroups with previously published results from surveys in other regions of the North Pacific. Individual identification photographs were used in mark–recapture analysis to estimate abundance for the Shumagin Island region. The best estimate was given by a modified Jolly–Seber method: N = 410 (95% CI: 241–683) for 2002. Comparison of photographs wi...

Functional Ecology, 2021

The relative energetic benefits of foraging on one type of prey rather than another are not easil... more The relative energetic benefits of foraging on one type of prey rather than another are not easily measured, particularly for large free-ranging predators. Nonetheless, assumptions about preferred and alternative prey are frequently made when predicting how a predator may impact its environment, adapt to environmental change, or interact with human activities. We developed and implemented a process-based model to investigate the potential energetic benefit (PEB) of in situ foraging opportunities in rorqual whales. The model integrates and evaluates the energetic importance of prey patch characteristics (prey distribution and predator avoidance) and predator characteristics (morphometrics, foraging tactics and feeding rates). We applied the model to test the assumption that hatchery-released juvenile salmon are an &amp;quot;easy meal&amp;quot; for humpback whales compared to more common prey, herring and krill. In eleven out of the thirteen foraging situations modeled, whales were found to be feeding in a manner where net energy gain was greater than the energetic costs of non-foraging swimming, consistent with optimal foraging theory. Humpback whale PEB for hatchery-released juvenile salmon fell within the range of the PEB for krill and herring but varied by species, from relatively high PEB for chum salmon to relatively low for coho salmon. Our model provides behavioral insight as well, indicating that shallow feeding may be more important for reducing energy expenditure through slower lunge speeds than for increasing prey capture. The model also provides a means of identifying prey patch characteristics, with prey aggregation playing the largest role in determining PEB despite being a poor overall proxy for PEB, supporting the use of the complex model framework. Modeling approaches are especially valuable where they can use reasonable assumptions to substitute for a lack of reliable observations, thereby integrating a range of interacting factors into a single framework. Additionally, because process-based models can make predic [...]

ICES Journal of Marine Science, 2015

Since 2003, a collaborative effort (SEASWAP) between fishers, scientists, and managers has resear... more Since 2003, a collaborative effort (SEASWAP) between fishers, scientists, and managers has researched how Alaskan sperm whales locate demersal longline fishing activity and then depredate sablefish from gear. Sperm whales constantly produce relatively low-frequency biosonar signals whenever foraging; therefore, over the past decade, passive acoustic monitoring (PAM) has become a basic tool, used for both measuring depredation activity and accelerating field tests of potential depredation countermeasures. This paper reviews and summarizes past published PAM research on SEASWAP, and then provides a detailed example of how PAM methods are currently being used to test countermeasures. The review covers two major research thrusts: (i) identifying acoustic outputs of fishing vessels that provide long-distance “cues” that attract whales to fishing activity; and (ii) validating whether distinctive “creak” sounds can be used to quantify and measure depredation rates, using both bioacoustic t...

Marine Ecology Progress Series, 2013

We quantified the relative influence of maternal fidelity to feeding grounds and natal fidelity t... more We quantified the relative influence of maternal fidelity to feeding grounds and natal fidelity to breeding grounds on the population structure of humpback whales Megaptera novaeangliae based on an ocean-wide survey of mitochondrial (mt) DNA diversity in the North Pacific. For 2193 biopsy samples collected from whales in 10 feeding regions and 8 breeding regions during the winter and summer of 2004 to 2006, we first used microsatellite genotyping (average, 9.5 loci) to identify replicate samples. From sequences of the mtDNA control region (500 bp) we identified 28 unique haplotypes from 30 variable sites. Haplotype frequencies differed markedly among feeding regions (overall F ST = 0.121, Φ ST = 0.178, p < 0.0001), supporting previous evidence of strong maternal fidelity. Haplotype frequencies also differed markedly among breeding regions (overall F ST = 0.093, Φ ST = 0.106, p < 0.0001), providing evidence of strong natal fidelity. Although sex-biased dispersal was not evident, differentiation of microsatellite allele frequencies was weak compared to differentiation of mtDNA haplotypes, suggesting male-biased gene flow. Feeding and breeding regions showed significant differences in haplotype frequencies, even for regions known to be strongly connected by patterns of individual migration. Thus, the influence of migratory fidelity seems to operate somewhat independently on feeding and breeding grounds over an evolutionary time scale. This results in a complex population structure and the potential to define multiple units to conserve in either seasonal habitat.

The Journal of the Acoustical Society of America, 2008

In July 2007 bioacoustic tags were attached to adult sperm whales in the Gulf of Alaska under bot... more In July 2007 bioacoustic tags were attached to adult sperm whales in the Gulf of Alaska under both natural foraging conditions, and situations wherein the animals were depredating sablefish from commercial longlining vessels. A small Rigid-Hull Inflatable was used to approach and attach a suction-cup acoustic recording tag on 13 occasions and stayed on animals for a total of 168 hours, yielding 80 hours of depth, orientation, and acoustic data. These results, combined with passive acoustic tracking and underwater video-camera data, indicate that sperm whales depredate at depths shallower than 50 m, compared to natural foraging depths of 300-400 m in the area. During depredation the animals demonstrate changes in pitch and roll that are greater when compared with normal foraging behavior. Observations on the acoustic behavior of the animals are noted as well. The fact that these normally deep-diving animals depredate so close to the surface has interesting implications for both depredation-reduction strategies and biosonar research.

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Sperm whales (Physeter macrocephalus) remove fish from longline fishing gear. This behavior is ca... more Sperm whales (Physeter macrocephalus) remove fish from longline fishing gear. This behavior is calle…

The long-term goal of this work is to develop techniques for tracking marine mammal sounds in ran... more The long-term goal of this work is to develop techniques for tracking marine mammal sounds in range and depth from a single mooring or platform (e.g. glider), by exploiting the propagation effects of the deep-water sound speed channel. Most listening platforms currently use a single hydrophone to detect events, making no effort at localization. For beaked whales (which have a limited detection range of about 5-7 km), detection may be sufficient to determine whether an animal is close to potential naval operations, but for most species, one needs to assume a typical source level (or source level distribution) to translate a detection's received level into a distance, a risky assumption that generates large uncertainties in position, which in turn degrades attempts at acoustic density estimation and makes mitigation decisions problematic.

Marine Ecology Progress Series, Dec 15, 2016

Humpback whales Megaptera novaeangliae are filter feeders that use discrete lunges to effectively... more Humpback whales Megaptera novaeangliae are filter feeders that use discrete lunges to effectively capture densely aggregated prey. The objective of this research was to examine how foraging humpback whales in Southeast Alaska responded to varying prey patch densities and depths. Digital acoustic recording tags (DTAGs; n = 6) were deployed and focal follows were conducted on foraging whales in Sitka Sound, Alaska in September 2012. Prey density was recorded around tagged whales using a Simrad EK60 scientific echosounder and ground-truthed with net tows. Lunges were identified from peaks in jerk in the accelerometer signal, and krill were identified from echosounder data using decibel differencing. Lunge depth was 111 ± 9 m (mean ± SD) for the shallowest diving whale (foraging past sunset) and 144 ± 7 (mean ± SD) m for the deepest diving whale (foraging diurnally). Ninety-five percent of lunges occurred within a 300 m and 30 min spatio-temporal buffer of krill, indicating that tagged whales fed on krill. Generalized additive mixed model (GAMM) results for spatio-temporally integrated prey and lunge data indicated that mean volume backscattering strength, a proxy for krill density, and krill depth significantly affected the occurrence of a lunge (density: p = 0.006, depth: p < 0.001). Whales fed in the densest region of the krill layer, where mean volume backscatter was −57 dB (range: −50 to −81 dB re 1 m −1 at 120 kHz). By targeting the densest prey layer, whales maximized their energetic gain by capturing the most prey with each lunge.

We present an ocean-basin-scale dataset that includes tail fluke photographic identification (pho... more We present an ocean-basin-scale dataset that includes tail fluke photographic identification (photo-ID) and encounter data for most living individual humpback whales (Megaptera novaeangliae) in the North Pacific Ocean. The dataset was built through a broad collaboration combining 39 separate curated photo-ID catalogs, supplemented with community science data. Data from throughout the North Pacific were aggregated into 13 regions, including six breeding regions, six feeding regions, and one migratory corridor. All images were compared with minimal pre-processing using a recently developed machine learning artificial intelligence image recognition algorithm capable of rapidly detecting matches between individuals to an estimated 97–99% accuracy. For the study period of 2001 to 2021, a total of 27,956 unique individuals were documented in 157,350 encounters. Each individual was encountered, on average, in 5.6 sampling periods (i.e., breeding and feeding seasons), with an annual average...

We present an ocean-basin-scale dataset that includes tail fluke photographic identification (pho... more We present an ocean-basin-scale dataset that includes tail fluke photographic identification (photo-ID) and encounter data for the majority of living individual humpback whales (Megaptera novaeangliae) in the North Pacific Ocean. The dataset was built through a broad collaboration combining 39 separate curated photo-ID catalogs supplemented with community science data. All available images were compared using a recently developed machine learning artificial intelligence image recognition algorithm able to rapidly and accurately detect matches between individuals. For the study period of 2001 to 2021, a total of 27,956 unique individuals were documented in 157,379 encounters, with each individual encountered, on average, in 5.6 sampling periods (i.e., breeding and feeding seasons), and with an annual average of 87.1% of whales encountered in more than one season. The combined dataset and image recognition tool represents a living and accessible resource for collaborative, basin-wide ...

The American Naturalist, 2022

The distributions of marine ectotherms are governed by physiological sensitivities to long-term t... more The distributions of marine ectotherms are governed by physiological sensitivities to long-term trends in seawater temperature and dissolved oxygen. Short-term variability in these parameters has the potential to facilitate rapid range expansions, and the resulting ecological and socioeconomic consequences may portend those of future marine communities. Here, we combine physiological experiments with ecological and demographic surveys to assess the causes and consequences of sudden but temporary poleward range expansions of a marine ectotherm with considerable life history plasticity (California market squid, Doryteuthis opalescens). We show that sequential factors related to resource accessibility in the core range—the buildup of large populations as a result of competitive release and climate-associated temperature increase and oxygen loss that constrain aerobic activity—may drive these expansions. We also reveal that poleward range expansion alters the body size—and therefore trophic role—of invading populations, with potential negative implications for socioeconomically valuable resident species. To help forecast rapid range expansions of marine ectotherms, we advocate that research efforts focus on factors impacting resource accessibility in core ranges. Determining how environmental conditions in receiving ecosystems affect body size and how body size is related to trophic role will help refine estimates of the impacts of future marine communities.

Animals, 2022

Stranded large whales represent an opportunity to learn about the anatomy and health of these cry... more Stranded large whales represent an opportunity to learn about the anatomy and health of these cryptic free-ranging animals. However, where time and access is frequently limited, law enforcement and management priorities often take precedence over research, outreach, and educational uses. On 14 March 2021, a dead female adult humpback whale was reported stranded on an uninhabited island 15 miles west of Sitka, Alaska. The whale was three-dimensionally scanned using light detection and ranging (LiDAR) and photogrammetry before, during, and at multiple time points after a necropsy, including full decomposition 17 days later (NOAA Fisheries permit 18786-01). These scans were organized and displayed on the site Sketchfab with annotations and made publically available as a “4D virtual necropsy” (the fourth dimension is time). After one month, our user survey indicated widespread interest in the platform by both the local community and worldwide by stranding professionals, researchers, and...

: To promote the use of endocrine techniques to advance our knowledge of the physiology of cetace... more : To promote the use of endocrine techniques to advance our knowledge of the physiology of cetaceans and their responses to change in their environment.

Environmental and Ecological Statistics, 2014

In Prince William Sound (PWS), changes in abundance of humpback whales (Megaptera novaeangliae), ... more In Prince William Sound (PWS), changes in abundance of humpback whales (Megaptera novaeangliae), one of PWS's primary marine predator species, have until now been largely unknown. Using a historical dataset (1978-2009), we constructed the first time series of estimated humpback whale abundance in western PWS that is also one of the longest time series used in analyses of humpback whale mark-recapture data.

The Journal of the Acoustical Society of America, 2014

For decades off SE Alaska, sperm whales have located longlining fishing vessels and removed, or “... more For decades off SE Alaska, sperm whales have located longlining fishing vessels and removed, or “depredated,” black cod from the hauls. In 2004, the Southeast Alaska Sperm Whale Avoidance Project (SEASWAP) began deploying passive acoustic recorders on longline fishing gear in order to identify acoustic cues that may alert whales to fishing activity. It was found that when hauling, longlining vessels generate distinctive cavitation sounds, which served to attract whales to the haul site. The combined use of underwater recorders and video cameras also confirmed that sperm whales generated “creak/buzz” sounds while depredating, even under good visual conditions. By deploying recorders with federal sablefish surveys over two years, a high correlation was found between sperm whale creak rate detections and visual evidence for depredation. Thus passive acoustics is now being used as a low-cost, remote sensing method to quantify depredation activity in the presence and absence of various d...

Marine Mammal Science, 2007

Female humpback whales in southeastern Alaska have never been observed with their first calf at a... more Female humpback whales in southeastern Alaska have never been observed with their first calf at ages 5 to 7 years, the documented age at first reproduction in the Gulf of Maine humpback whale population. Long-term sighting histories of 10 individually identified females of known age in southeastern Alaska were used to address this issue. These females were sighted with their first calf at ages 8-16 (mean 11.8) years, significantly older than observed in the Gulf of Maine where 5.91 years is the mean age at first calving. We summarize potential sources of bias and other factors that likely contributed to the difference in age at first calving. Despite their limitations, these are the only available data to assess the age at first calving in North Pacific humpback whales. Figure 1. Stable markings on the ventral tail flukes of humpback whales, like this one photographed in Glacier Bay, Alaska, allow individuals to be identified over many years.

The Journal of the Acoustical Society of America, 2013

Annual federal stock assessment surveys for Alaskan sablefish also attempt to measure sperm whale... more Annual federal stock assessment surveys for Alaskan sablefish also attempt to measure sperm whale depredation by quantifying visual evidence of depredation, including lip remains and damaged fish. An alternate passive acoustic method for quantifying depredation was investigated during the 2011 and 2012 survey hauls. A combination of machine-aided and human analysis counted the number of distinct “creak” sounds detected on autonomous recorders deployed during the survey, emphasizing sounds that are followed by a period of silence (“creak-pauses”), a possible indication of prey capture. These raw counts were then adjusted for variations in background noise levels between deployments. For most locations, the noise-adjusted counts of “creak-pauses” were highly correlated with survey counts of lip remains during both years (2012: r(10) = 0.89, p = 1e-3; 2011: r(39) = 0.72, p = 4e-3) and somewhat correlated with observed sablefish damage in 2011 [r(39) = 0.37, p = 0.03], but uncorrelated ...

Canadian Journal of Zoology, 2004

Despite extensive research on humpback whales (Megaptera novaeangliae (Borowski, 1781)) in parts ... more Despite extensive research on humpback whales (Megaptera novaeangliae (Borowski, 1781)) in parts of the North Pacific, little research has focused on the whales feeding in coastal waters west of Kodiak Island in the Gulf of Alaska. To extend research westward in the North Pacific, small-boat surveys were conducted near the Shumagin Islands during the summers of 1999–2002. Photographs of the natural markings of humpback whales were collected, representing 413 sightings of 171 individual whales. Small samples of skin tissue were collected from 20 individuals, including two mother–calf pairs, for sex identification and comparison of mtDNA haplogroups with previously published results from surveys in other regions of the North Pacific. Individual identification photographs were used in mark–recapture analysis to estimate abundance for the Shumagin Island region. The best estimate was given by a modified Jolly–Seber method: N = 410 (95% CI: 241–683) for 2002. Comparison of photographs wi...

Functional Ecology, 2021

The relative energetic benefits of foraging on one type of prey rather than another are not easil... more The relative energetic benefits of foraging on one type of prey rather than another are not easily measured, particularly for large free-ranging predators. Nonetheless, assumptions about preferred and alternative prey are frequently made when predicting how a predator may impact its environment, adapt to environmental change, or interact with human activities. We developed and implemented a process-based model to investigate the potential energetic benefit (PEB) of in situ foraging opportunities in rorqual whales. The model integrates and evaluates the energetic importance of prey patch characteristics (prey distribution and predator avoidance) and predator characteristics (morphometrics, foraging tactics and feeding rates). We applied the model to test the assumption that hatchery-released juvenile salmon are an &amp;quot;easy meal&amp;quot; for humpback whales compared to more common prey, herring and krill. In eleven out of the thirteen foraging situations modeled, whales were found to be feeding in a manner where net energy gain was greater than the energetic costs of non-foraging swimming, consistent with optimal foraging theory. Humpback whale PEB for hatchery-released juvenile salmon fell within the range of the PEB for krill and herring but varied by species, from relatively high PEB for chum salmon to relatively low for coho salmon. Our model provides behavioral insight as well, indicating that shallow feeding may be more important for reducing energy expenditure through slower lunge speeds than for increasing prey capture. The model also provides a means of identifying prey patch characteristics, with prey aggregation playing the largest role in determining PEB despite being a poor overall proxy for PEB, supporting the use of the complex model framework. Modeling approaches are especially valuable where they can use reasonable assumptions to substitute for a lack of reliable observations, thereby integrating a range of interacting factors into a single framework. Additionally, because process-based models can make predic [...]

ICES Journal of Marine Science, 2015

Since 2003, a collaborative effort (SEASWAP) between fishers, scientists, and managers has resear... more Since 2003, a collaborative effort (SEASWAP) between fishers, scientists, and managers has researched how Alaskan sperm whales locate demersal longline fishing activity and then depredate sablefish from gear. Sperm whales constantly produce relatively low-frequency biosonar signals whenever foraging; therefore, over the past decade, passive acoustic monitoring (PAM) has become a basic tool, used for both measuring depredation activity and accelerating field tests of potential depredation countermeasures. This paper reviews and summarizes past published PAM research on SEASWAP, and then provides a detailed example of how PAM methods are currently being used to test countermeasures. The review covers two major research thrusts: (i) identifying acoustic outputs of fishing vessels that provide long-distance “cues” that attract whales to fishing activity; and (ii) validating whether distinctive “creak” sounds can be used to quantify and measure depredation rates, using both bioacoustic t...

Marine Ecology Progress Series, 2013

We quantified the relative influence of maternal fidelity to feeding grounds and natal fidelity t... more We quantified the relative influence of maternal fidelity to feeding grounds and natal fidelity to breeding grounds on the population structure of humpback whales Megaptera novaeangliae based on an ocean-wide survey of mitochondrial (mt) DNA diversity in the North Pacific. For 2193 biopsy samples collected from whales in 10 feeding regions and 8 breeding regions during the winter and summer of 2004 to 2006, we first used microsatellite genotyping (average, 9.5 loci) to identify replicate samples. From sequences of the mtDNA control region (500 bp) we identified 28 unique haplotypes from 30 variable sites. Haplotype frequencies differed markedly among feeding regions (overall F ST = 0.121, Φ ST = 0.178, p < 0.0001), supporting previous evidence of strong maternal fidelity. Haplotype frequencies also differed markedly among breeding regions (overall F ST = 0.093, Φ ST = 0.106, p < 0.0001), providing evidence of strong natal fidelity. Although sex-biased dispersal was not evident, differentiation of microsatellite allele frequencies was weak compared to differentiation of mtDNA haplotypes, suggesting male-biased gene flow. Feeding and breeding regions showed significant differences in haplotype frequencies, even for regions known to be strongly connected by patterns of individual migration. Thus, the influence of migratory fidelity seems to operate somewhat independently on feeding and breeding grounds over an evolutionary time scale. This results in a complex population structure and the potential to define multiple units to conserve in either seasonal habitat.

The Journal of the Acoustical Society of America, 2008

In July 2007 bioacoustic tags were attached to adult sperm whales in the Gulf of Alaska under bot... more In July 2007 bioacoustic tags were attached to adult sperm whales in the Gulf of Alaska under both natural foraging conditions, and situations wherein the animals were depredating sablefish from commercial longlining vessels. A small Rigid-Hull Inflatable was used to approach and attach a suction-cup acoustic recording tag on 13 occasions and stayed on animals for a total of 168 hours, yielding 80 hours of depth, orientation, and acoustic data. These results, combined with passive acoustic tracking and underwater video-camera data, indicate that sperm whales depredate at depths shallower than 50 m, compared to natural foraging depths of 300-400 m in the area. During depredation the animals demonstrate changes in pitch and roll that are greater when compared with normal foraging behavior. Observations on the acoustic behavior of the animals are noted as well. The fact that these normally deep-diving animals depredate so close to the surface has interesting implications for both depredation-reduction strategies and biosonar research.