Acoustic monitoring reveals the times and tides of harbor porpoise <i>(Phocoena phocoena)</i> distribution off central Oregon, U.S.A.

Holdman, Amanda K.; Haxel, J. H.; Klinck, Holger; Torres, Leigh G.

doi:10.1111/mms.12537

Cited by 7 publications

(5 citation statements)

References 78 publications

(179 reference statements)

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“…The partial dependence plots showed higher values during the night. A similar pattern was described by Holdman et al (2019). The higher harbor porpoise detections at night may reflect a higher prey availability.…”

Section: Discussionsupporting

confidence: 89%

“…For instance, a strong occurrence of harbor porpoises was predicted during high tide in a Dutch part of the Wadden Sea/North Sea (Ijsseldijk et al, 2015), in the Marsdiep area (Wadden Sea, Netherlands) (Boonstra et al, 2013), and in northwest Scotland (Marubini et al, 2009). By contrast, the presence of harbor porpoises correlated positively with ebb tide in a near‐shore site in southwest Wales, UK, (Pierpoint, 2008) and near‐shore in Oregon (Holdman et al, 2019). In the Ems Estuary, the greater presence of harbor porpoises during high tide could be explained by increased prey availability.…”

Section: Discussionmentioning

confidence: 99%

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Against all odds: Harbor porpoises intensively use an anthropogenically modified estuary

Taupp

2021

Marine Mammal Science

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Harbor porpoises (Cetacea) are present in the North Sea throughout the year but periodically enter adjacent estuaries, which due to human activities are among the planet's most threatened aquatic systems. However, the occurrence of harbor porpoises in estuaries has rarely been studied. In this work, harbor porpoise occurrence at two stations in the anthropogenically modified Ems Estuary (Germany, Netherlands) was modeled using a machine learning approach (Random Forest) that drew on 8 years of acoustic monitoring data with C-PODs together with environmental data.Harbor porpoises were present year-round at both stations.According to the models, their detection was mainly explained by season, tide, and noise level, with the highest detection probabilities in spring, at high tide, and at low noise levels. The seasonal and tide-dependent occurrence of harbor porpoises coincided with prey availability. Presumed feeding activity was detected in 47% of all harbor-porpoise-positive 10 min blocks and indicated the importance of the estuary as a regular feeding area. The elevated noise levels detected at one station were attributed to tidal-induced currents and sediment movements. The results of this study can help to improve estuarine management through measures that include conducting dredging and disposal activities when harbor porpoise occurrence is less likely.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Against all odds: Harbor porpoises intensively use an anthropogenically modified estuary

Taupp

2021

Marine Mammal Science

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“…The frequent presence of communication sequences and responding conspecifics could furthermore also be an indirect indicator of foraging, possibly representing cooperative foraging strategies [ 83 ]. Due to the described limitations with data logged by static acoustic recorders and additionally having data with incomplete click sequences, the sudden decrease of ICI below 10 ms is to date the best indicator for this method to classify foraging and has been regularly applied [ 26 , 47 , 49 , 52 , 85 , 86 , 87 ].…”

Section: Discussionmentioning

confidence: 99%

Time and tide: Seasonal, diel and tidal rhythms in Wadden Sea Harbour porpoises (Phocoena phocoena)

et al. 2019

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Odontocetes have evolved a rich diversity of prey- and habitat-specific foraging strategies, which allows them to feed opportunistically on locally and temporally abundant prey. While habitat-specific foraging strategies have been documented for some odontocete species, this is less known for the harbour porpoise (Phocoena phocoena). We collected multiple years of acoustic data using echolocation click loggers to analyse porpoise occurrence and buzzing behaviour, indicating feeding, in the German Wadden Sea (North Sea). Seasonal, diel and tidal effects were studied using Generalised Estimating Equations (GEE-GAMs). Locally season, time of day and tidal time significantly influenced the probability of porpoise detections and detection of foraging sequences (buzzes). Hunting strategies, and therefore frequency of buzzes, were likely affected by prey distribution and large differences between POD locations indicated that porpoises used highly specific behaviour adapted to tide and time of day to efficiently feed on the available prey. Strong seasonal and spatial variation in diel and tidal effects underline the importance of long-term observations. Studies on porpoise behaviour are often based on short-term observations and might rather reflect a seasonal than a general pattern. The results of this study show clearly that significant changes in porpoise behaviour can be found in short and long-term observations. Here some features are based on short term determinants and others are stable over years and care should be taken about drawing general conclusions based on local patterns. Highly variable spatio-temporal patterns indicate a high flexibility of porpoises in a highly variable environment and address a challenge for complex conservation management plans.

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“…Whilst the percentage of deviance explained by the model was relatively low (9%), there was sufficient statistical power to identify a significant behavioural response to operation of the turbine. It is not unusual for temporal models of cetacean occurrence to only explain a relatively small amount of the deviance (Holdman et al, 2018) and it is possible that porpoise presence in tidally energetic sites and at the spatial scale monitored is influenced by transient fine‐scale hydrographic features that were not considered in this study (Pierpoint, 2008). In general, it is not possible to use passive acoustic data to distinguish between absence, individuals that are present but not vocalizing, or individuals that are not detectable for some other reason, such as their orientation with respect to the receiving hydrophone.…”

Section: Discussionmentioning

confidence: 92%

Harbour porpoise (Phocoena phocoena) presence is reduced during tidal turbine operation

Palmer

Gillespie

Macaulay

et al. 2021

Aquatic Conservation

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Uptake of tidal turbine technology to generate renewable energy has been partly limited by poor understanding of ecological impacts, including the potential for collisions between cetaceans and rotating turbine blades. To address this concern, it is necessary to identify whether cetaceans behaviourally respond to operating turbines. A turbine in Scotland was instrumented with hydrophones to detect cetacean vocalizations. A generalized additive model was used to investigate temporal variability in harbour porpoise presence close to the turbine. As there were incidentally periods when the turbine was not operating, it was possible to determine the effect of blade rotation, whilst accounting for the potentially confounding effect of tidal flow. Harbour porpoise presence varied intra‐annually, diurnally and with tidal state. Peak presence occurred during winter (September–February), at night and at high flow speeds on the flood tide. Porpoises exhibited significant avoidance of the tidal turbine when it was operating; avoidance increased with flow speed, whereby mean porpoise presence was reduced by up to 78% (95% CIs, 51%, 91%) on the flood tide and up to 64% (95% CI, 3%, 91%) on the ebb tide. The temporal variability in encounter rate in the present study highlights that collision risk assessments assuming static densities probably fail to capture the temporal variability of collision risk. Future studies should conduct long‐term baseline monitoring to derive encounter rates at larger spatio‐temporal scales and as a reference from which to measure change in habitat use. It is also critical that the generality of the avoidance rates presented here is assessed for other sites, turbine types, array sizes and cetacean species. As the tidal industry expands, it will be important to reconcile the benefits of avoidance responses from a collision risk perspective with potential chronic effects of displacement from, or barriers between, important habitats.

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Acoustic monitoring reveals the times and tides of harbor porpoise (Phocoena phocoena) distribution off central Oregon, U.S.A.

Cited by 7 publications

References 78 publications

Against all odds: Harbor porpoises intensively use an anthropogenically modified estuary

Against all odds: Harbor porpoises intensively use an anthropogenically modified estuary

Time and tide: Seasonal, diel and tidal rhythms in Wadden Sea Harbour porpoises (Phocoena phocoena)

Harbour porpoise (Phocoena phocoena) presence is reduced during tidal turbine operation

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