Extracting foraging behavior from passive acoustic monitoring data to better understand harbor porpoise (Phocoena phocoena) foraging habitat use

Abstract

For odontocetes, passive acoustic monitoring (PAM) can be used to differentiate between occurrence and foraging through analysis of click characteristics. Feeding buzzes and navigation/searching echolocation clicks of harbor porpoise (Phocoena phocoena) were differentiated within C‐POD data from northwest Ireland between 2009 and 2017. The spatiotemporal distribution of foraging behavior was investigated using generalized additive modelling, at multiple temporal scales. Both the presence/absence of buzzes and foraging intensity (defined by buzz:click ratios) were determined. Feeding buzzes were identified in one third of porpoise positive hours, ranging from 15% in summer, to 40% in autumn, highlighting seasonal variation irrespective of porpoise occurrence. Complex interannual variation in foraging behavior was also shown across the time series. A strong nocturnal peak in foraging intensity was observed. We found increased porpoise foraging with dolphin species detections within the same hour, and a negative impact of construction activities, involving both impulsive and broadband noise. Results highlight the value of long‐term acoustic time series, by quantifying variation, and show that extracting foraging behavior from occurrence data can help to unravel habitat use patterns, responses to disturbance, and seasonal changes in behavior. Understanding when and how a species uses an area can better inform marine spatial planning and help mitigate anthropogenic impacts.

Warm oceans exacerbate Chinook salmon bycatch in the Pacific hake fishery driven by thermal and diel depth‐use behaviours

“…Chinook salmon moved between shallow water column depths during the day and deeper depths at night (Figure 3), which represents the opposite diel pattern of many marine fishes (Brierley, 2014; Hays, 2003). Salmon may be using daylight in surface waters for foraging or navigation and/or retreating deeper at night to avoid nocturnal, surface‐oriented marine predators (Byron & Burke, 2014; Tanaka et al, 2000; Todd et al, 2022; Wilson et al, 2014). Two tagging studies also found that the deepest Chinook salmon dives occurred at night; however, other studies have observed opposite and variable patterns (Arostegui et al, 2017; Courtney et al, 2019; Hinke, Foley et al, 2005).…”

Offshore construction using gravity-base foundations indicates no long-term impacts on dolphins and harbour porpoise

“…Studies of dolphin acoustic activity have suggested that several species echolocate at a lower rate during daylight hours, possibly relating to patterns in foraging activity or increased use of visual cues during this period (Soldevilla et al 2010a(Soldevilla et al , 2010bWang et al 2015). Previous studies of harbour porpoises off the west coast of Scotland (Carlström 2005), Dogger Bank (Todd et al 2009), and off north-western Ireland (Todd et al 2022) have demonstrated higher encounter rates at night containing higher click rates with minimum interclick intervals of < 10 ms (ms), indicative of increased foraging activities. The findings of our study suggest that harbour porpoises are either echolocating less in the development site at night, possibly in response to the construction and operation of the wind turbines, or that they have shifted their diel use at the site, perhaps associated with increased foraging opportunities granted by a possible reef-effect or reduction in fishing activity.…”

What the F‐POD? Comparing the F‐POD and C‐POD for monitoring of harbor porpoise (Phocoena phocoena)

“…Foraging buzzes are presumed prey capture attempts with a typical ICI of less than 10 ms (DeRuiter et al, 2009 ; Miller, 2010 ; Verfuß et al, 2009 ). Gaussian mixture models were used to categorize echolocation clicks based on their ICI (Berges et al, 2019 ; Pirotta, Brookes, et al, 2014 ; Pirotta, Thompson, et al, 2014 ; Todd et al, 2022 ). This method classifies log‐transformed ICIs to identify patterns of echolocation clicks.…”

“…Over the years PAM technology has greatly advanced the field of cetacean ecology, allowing a cost‐effective alternative to extensive visual surveys that are not reliant on daylight hours, favorable weather conditions, and availability of observers. Passive acoustic monitoring of cetaceans has resulted in temporally high‐resolution data providing us with insights into population size and abundance (Amundin et al, 2022 ; Marques et al, 2013 ), habitat use (Fleming et al, 2018 ; Palmer et al, 2019 ), and behavior (Malinka et al, 2021 ; Pirotta, Thompson, et al, 2014 ; Todd et al, 2022 ) for many species. Such technology is also fundamental for long‐term monitoring, particularly with the increase in coastal developments and potential disturbance from construction, marine renewable devices, shipping, and fisheries (e.g., Fernandez‐Betelu et al, 2022 ; Omeyer et al, 2020 ; Ramesh et al, 2021 ; Todd et al, 2020 , 2022 ).…”