Phocoena Phocoena Research Articles

Assessing the Effects of Banana Pingers as a Bycatch Mitigation Device for Harbour Porpoises (Phocoena phocoena)

Bycatch is a significant cause of population declines of marine megafauna globally. While numerous bycatch mitigation strategies exist, acoustic alarms, or pingers, are the most widely adopted strategy for small cetaceans. Although pingers have been shown to be an effective measure for numerous species, there are some concerns about their long-term use. Bycatch is recognised as a persistent problem in waters around Cornwall, United Kingdom, where several cetacean species are resident, with harbour porpoises (Phocoena phocoena) being the most-commonly sighted. In this study, we assessed the effects of a Banana Pinger (Fishtek Marine Limited) on harbour porpoises in Cornwall between August 2012 and March 2013. Two passive acoustic loggers (C-PODs; Chelonia Limited) were deployed 100m apart to record cetacean activity during cycles of active and inactive pinger periods. Harbour porpoises were 37% less likely to be detected at the C-POD near the pinger when the pinger was active, while they were only 9% less likely to be detected 100m further away. The effect of the pinger was constant over the study period at both C-PODs despite the temporal variation in harbour porpoise detections. In addition, we found no evidence of reduced pinger effect with changing environmental conditions. Furthermore, harbour porpoise detections at the C-POD near the pinger did not depend on the time elapsed since the pinger turned off, with harbour porpoises returning to the ensonified area with no delay. Together these results suggest that (1) harbour porpoises did not habituate to the pinger over an eight-month period, (2) the pinger effect is very localised, and (3) pinger use did not lead to harbour porpoise displacement over the study period, suggesting an absence of long-term behavioural effects. We suggest that the deployment of pingers on fishing nets would likely reduce net-porpoise interactions, thereby mitigating bycatch of harbour porpoises and potentially other cetacean species. As the small-scale fishery dominates in UK waters, there is an acute need for cost-effective mitigation strategies with concurrent monitoring to be implemented rapidly in order to address the problem of harbour porpoise, and more generally, cetacean bycatch.

Temporary Hearing Threshold Shift in Harbor Porpoises (Phocoena phocoena) Due to One-Sixth-Octave Noise Bands at 63 kHz

Temporary Hearing Threshold Shift in Harbor Porpoises (Phocoena phocoena) Due to One-Sixth-Octave Noise Bands at 63 kHz

Seal Bomb Noise as a Potential Threat to Monterey Bay Harbor Porpoise

Anthropogenic noise is a known threat to marine mammals. Decades of research have shown that harbor porpoises are particularly sensitive to anthropogenic noise, and geographic displacement is a common impact from noise exposure. Small, localized populations may be particularly vulnerable to impacts associated with displacement, as animals that are excluded from their primary habitat may have reduced foraging success and survival, or be exposed to increased threats of predation or bycatch. Seal bombs are underwater explosives used in purse seine fisheries to deter marine mammals during fishery operations. Pinnipeds are believed to be the primary target for seal bomb use, however there may be indirect impacts on harbor porpoises. Active purse seine fishing using seal bombs in the greater Monterey Bay area may, at times, span the entire range of the Monterey Bay harbor porpoise stock, which may lead to negative impacts for this population. In this contribution, we review anthropogenic noise as a threat to harbor porpoise, with a focus on the potential for impacts from seal bomb noise exposure in the Monterey Bay region.

Levels of Polychlorinated Biphenyls Are Still Associated with Toxic Effects in Harbor Porpoises (Phocoena phocoena) Despite Having Fallen below Proposed Toxicity Thresholds.

Polychlorinated biphenyls (PCBs) are toxic, persistent, and lipophilic chemical compounds that accumulate to high levels in harbor porpoises (Phocoena phocoena) and other cetaceans. It is important to monitor PCBs in wildlife, particularly in highly exposed populations to understand if concentrations are declining and how levels relate to toxicological thresholds and indices of health like infectious disease mortality. Here we show, using generalized additive models and tissue samples of 814 U.K.-stranded harbor porpoises collected between 1990 and 2017, that mean blubber PCB concentrations have fallen below the proposed thresholds for toxic effects. However, we found they are still associated with increased rates of infectious disease mortality such that an increase in PCB blubber concentrations of 1 mg kg-1 lipid corresponds with a 5% increase in risk of infectious disease mortality. Moreover, rates of decline and levels varied geographically, and the overall rate of decline is slow in comparison to other pollutants. We believe this is evidence of long-term preservation in the population and continued environmental contamination from diffuse sources. Our findings have serious implications for the management of PCB contamination in the U.K. and reinforce the need to prevent PCBs entering the marine environment to ensure that levels continue to decline.

Using passive acoustic monitoring to investigate the occurrence of cetaceans in a protected marine area in northwest Ireland

Under the EU Habitats Directive, cetacean species must be maintained at favourable conservation status in European waters. Whether this is achieved via protected area designation, curtailment of activities such as fishing or construction, or time restrictions on noise, it is dependent on understanding the temporal patterns in occurrence. Our ability to study this is often limited by the relatively short time-series of data available to researchers. This study uses nine years of passive acoustic monitoring data paired with environmental covariates to better understand the spatio-temporal dynamics of harbour porpoise and dolphin species using generalised estimating equations-generalised linear models (GEE-GLMs). This long-term time-series included periods of increased disturbance due to construction of an underwater gas pipeline in the area, enabling us to investigate the effect of construction on species occurrence. Harbour porpoise and dolphins occurred in every season, with detections peaking in winter. We found a negative association between dolphins and porpoises throughout the year. Inter-annual variation in occurrence was evident, with a cyclical bi-annual pattern highlighted for both species suggesting a complex pattern of movement. Construction activity had a significant negative effect on the presence of porpoise but not dolphins. However, no long-term decrease in detection rates of porpoise was recorded. This study highlights the importance of understanding what factors influence cetacean occurrence as well as the temporal scale of disturbance effects for planning and management of construction activities in coastal areas.

Juvenile harbor porpoises in the UK are exposed to a more neurotoxic mixture of polychlorinated biphenyls than adults

Polychlorinated biphenyls (PCBs) are a group of 209 persistent and bio-accumulative toxic pollutants present as complex mixtures in human and animal tissues. Harbor porpoises accumulate some of the highest levels of PCBs because they are long-lived mammals that feed at a high trophic level. Studies typically use the sum of a suite of individual chlorobiphenyl congeners (CBs) to investigate PCBs in wildlife. However, toxic effects and thresholds of CB congeners differ, therefore population health risks of exposure may be under or over-estimated dependent on the congener profiles present. In this study, we found congener profiles varied with age, sex and location, particularly between adult females and juveniles. We found that adult females had the highest proportions of octa-chlorinated congeners whilst juveniles had the highest proportions of tri- and tetra-chlorinated congeners. This is likely to be a consequence of pollutant offloading between mothers and calves during lactation. Analysis of the individual congener toxicities found that juveniles were exposed to a more neurotoxic CB mixture at a time when they were most vulnerable to its effects. These findings are an important contribution towards our understanding of variation in congener profiles and the potential effects and threats of PCB exposure in cetaceans.

Effect of a Bubble Screen on the Behavioral Responses of Captive Harbor Porpoises (Phocoena phocoena) Exposed to Airgun Sounds

Effect of a Bubble Screen on the Behavioral Responses of Captive Harbor Porpoises (Phocoena phocoena) Exposed to Airgun Sounds

Behavioral Responses of a Harbor Porpoise (Phocoena phocoena) to a Series of Four Different Simulated Low-Frequency Sonar Sounds (1.33-1.43 kHz)

Behavioral Responses of a Harbor Porpoise (Phocoena phocoena) to a Series of Four Different Simulated Low-Frequency Sonar Sounds (1.33-1.43 kHz)

Clinical, pathological, and laboratory diagnoses of diseases of harbour porpoises (Phocoena phocoena), live stranded on the Dutch and adjacent coasts from 2003 to 2016

Harbour porpoises (Phocoena phocoena) in the North Sea live in an environment heavily impacted by humans, the consequences of which are a concern for their health. Autopsies carried out on stranded harbour porpoises provide an opportunity to assess health problems in this species. We performed 61 autopsies on live-stranded harbour porpoises, which died following admission to a rehabilitation centre between 2003 and 2016. The animals had stranded on the Dutch (n = 52) and adjacent coasts of Belgium (n = 2) and Germany (n = 7). We assigned probable causes for stranding based on clinical and pathological criteria. Cause of stranding was associated in the majority of cases with pathologies in multiple organs (n = 29) compared to animals with pathologies in a single organ (n = 18). Our results show that the three most probable causes of stranding were pneumonia (n = 35), separation of calves from their mother (n = 10), and aspergillosis (n = 9). Pneumonia as a consequence of pulmonary nematode infection occurred in 19 animals. Pneumonia was significantly associated with infection with Pseudalius inflexus, Halocercus sp., and Torynurus convolutus but not with Stenurus minor infection. Half of the bacterial pneumonias (6/12) could not be associated with nematode infection. Conclusions from this study are that aspergillosis is an important probable cause for stranding, while parasitic infection is not a necessary prerequisite for bacterial pneumonia, and approximately half of the animals (29/61) probably stranded due to multiple causes. An important implication of the observed high prevalence of aspergillosis is that these harbour porpoises suffered from reduced immunocompetence.

Morphological and Pathological Findings in the Middle and Inner Ears of Harbour Porpoises (Phocoena phocoena)

Hearing represents the major sense in harbour porpoises (Phocoena phocoena) and impairment of hearing has a great impact on the survival of these animals. In this communication, some anatomical and histological aspects of the tympanoperiotic complex of harbour porpoises are presented. In addition, the ears of 21 incidentally bycaught or stranded freshly dead harbour porpoises of different age groups and sex were investigated histologically. At the entrance to the middle ear cavity, mucosa-associated lymphoid tissue was present that was often hyperplastic in juvenile (9/10) and adult individuals (7/8). Solitary lymphoid follicles were additionally found in the corpus cavernosum and adjacent to the stapedius muscle in single porpoises. The nematode Stenurus minor represented the most common pathogen observed in the middle ear cavity of juvenile and adult harbour porpoises and the parasite was associated with chronic inflammation with metaplastic and hyperplastic epithelial changes. An unusual bone formation at the attachment of the corpus cavernosum to the perioticum was a common finding, even in young individuals. Whether this represents a normal structure or a metaplastic change remains undetermined. Acute haemorrhages in the cochlea and/or the tympanic cavity occurred in all animals and were most likely agonal changes. Single porpoises suffered from purulent otitis media, mycotic otitis media with osteolysis or chronically fractured tympanic bones, likely causing impairment of hearing that may have contributed to by-catch. There was no evidence that stranding in five porpoises was associated with the aural changes. Histological examination of the ears in harbour porpoises is a valuable part of the assessment of their health status. Damage to hearing structures may explain starvation due to impaired ability to catch prey or unusual behaviour such as stranding or entanglement in nets.

Time of arrival difference estimation for narrow band high frequency echolocation clicks.

Algorithms are presented for the accurate time of arrival difference estimation of high frequency narrow band echolocation clicks from Harbor Porpoise. These clicks typically have a center frequency of around 130 kHz (wavelength ∼1.2 cm) and duration of <0.1 ms. When using hydrophones spaced centimeters apart, spatial aliasing can cause large errors on inter-hydrophone timing measurements due to the incorrect peak in the cross-correlation function of two signals being selected. It is shown that at sample rates of less than about 6 times the fundamental frequency, the incorrect correlation peak will be selected in 55% of measurements leading to large errors in time of arrival estimates. For clicks with a SNR > 10 dB these errors can be reduced by over two orders of magnitude through a combination of up-sampling the data and parabolic interpolation of peaks in the cross-correlation functions.

Temporary Hearing Threshold Shift in Harbor Porpoises (Phocoena phocoena) Due to One-Sixth-Octave Noise Band at 32 kHz

Temporary hearing threshold shift (TTS) caused by fatiguing sounds in the 1.5 to 16 kHz range has been documented in harbor porpoises (Phocoena phocoena). To assess impacts of anthropogenic noise on porpoise hearing, TTS needs to be investigated for other frequencies, as susceptibility appears to depend on the frequency of the fatiguing sound. TTS was quantified after two porpoises (Porpoises F05 and M06) were exposed for 1 hour to a continuous one-sixth-octave noise band centered at 32 kHz, at average received sound pressure levels of 118 to 148 dB re 1 µPa, and at a sound exposure level (SEL) range of 154 to 184 dB re 1 µPa2s. Hearing thresholds for 32, 44.8, and 63 kHz tonal signals were determined before and after exposure to quantify initial TTS and recovery. Porpoise M06’s hearing was tested 1 to 4 min after exposure. At 32 kHz, the lowest SEL that resulted in significant TTS1-4 (3.4 dB) was 166 dB re 1 µPa2s. At 44.8 kHz, the lowest SEL that resulted in significant TTS1-4 (5.2 dB) was 178 dB re 1 µPa2s. The highest TTS1-4 (18.3 dB) occurred at 44.8 kHz after exposure to 184 dB SEL. Porpoise F05’s hearing was tested 12 to 16 min after exposure. At 32 kHz, the lowest SEL that resulted in significant TTS12-16 (3.5 dB) was 184 dB re 1 µPa2s. At 44.8 kHz, the lowest SEL that resulted in significant TTS12-16 (1.2 dB) was 178 dB re 1 µPa2s. The highest TTS12-16 (8.2 dB) occurred in Porpoise F05 at 44.8 kHz after exposure to 184 dB SEL. At 63 kHz, no TTS could be elicited in either animal. Considering that Porpoise F05 had more time than Porpoise M06 for recovery, the susceptibility of the two porpoises to TTS after exposure to sounds of 32 kHz was similar. In the range investigated so far (1.5 to 32 kHz), susceptibility to TTS appears to increase with increasing frequency below ~6.5 kHz, and to decrease with increasing frequency above ~6.5 kHz.

A Soft‐Robotic Harbor Porpoise Pectoral Fin Driven by Coiled Polymer Actuators as Artificial Muscles

A Soft‐Robotic Harbor Porpoise Pectoral Fin Driven by Coiled Polymer Actuators as Artificial Muscles

A Soft‐Robotic Harbor Porpoise Pectoral Fin Driven by Coiled Polymer Actuators as Artificial Muscles

Biomimicry is an approach in science and engineering to overcome human challenges by designing materials and systems modeled after nature. Selected applications of biomimicry include catheters, hearing devices, and artificial appendages such as arms, legs, and fingers. The inspiration for this study is the hydrofoil‐like structured pectoral fin of the harbor porpoise whale that is ultimately useful for studying fluid‐structure interactions, drag, lift, and laminar‐to‐turbulent transitions. The pectoral fin is fabricated by manipulating computed tomography (CT) scans into 3D models using Simpleware ScanIP and post‐processed in Autodesk for printing. An array of thermally driven coiled polymer actuators (CPA) fabricated from nylon and heated with Nichrome are used as artificial muscles for the fabricated pectoral fin. The CPAs are of great interest due to its high specific power and large actuation stroke. The work discussed includes the fabrication of the fin (designing, printing, and assembly), the fabrication and testing of the CPAs, implementation of the CPAs, controlling, and actuation of the bio‐inspired whale fin.

Effect of Pile-Driving Playback Sound Level on Fish-Catching Efficiency in Harbor Porpoises (Phocoena phocoena)

The foundations of offshore wind turbine parks are often constructed by means of percussion pile driving. Broadband impulsive sounds generated by pile driving may disturb and distract marine mammals such as harbor porpoises (Phocoena phocoena); their concentration may be reduced, affecting the skills they need for foraging (e.g., timing and precision) or reducing their ability to catch prey and, thus, their foraging efficiency. The resulting reduction in fitness may eventually lead to population declines. Therefore, it is important to understand the effects of these anthropogenic sounds on the ability of harbor porpoises to catch fish. Two captive harbor porpoises (porpoise F05 and porpoise M06) performed a fish-catching task (i.e., retrieving dead fish from a net feeding cage) while they were exposed to low ambient noise (quiet conditions) and impulsive pile-driving playback sounds at three (porpoise M06) or four (porpoise F05) mean received single-strike sound exposure levels (SELss) between 125 and 143 dB re 1 µPa2s. The two study animals differed in their fish-catching success rate at all noise levels, including under quiet conditions: Porpoise F05 was less likely to catch fish than porpoise M06. They also responded differently to increasing SELss: Only porpoise F05 was significantly more likely to terminate trials and less likely to catch fish as SELss increased above 134 dB, but her trial failure rate remained unaffected by increasing SELss. The time taken to catch a fish did not vary with SELss but was slightly longer for porpoise F05 than for porpoise M06. Results suggest that high-amplitude pile driving sounds are likely to negatively affect foraging in some harbor porpoises by decreasing their catch success rate and increasing the termination rate of their fish-catching attempts; the severity of the effects is likely to increase with increasing pile driving SELss. However, individual differences in responses to sound, termination rates, and fish-catching success (even in ambient conditions) may complicate the quantification of the impacts of pile driving sounds on harbor porpoises.

High Levels of Food Intake in Harbor Porpoises (Phocoena phocoena): Insight into Recovery from Disturbance

If harbor porpoises (Phocoena phocoena) are impaired in their foraging ability because they need to move away from anthropogenic sound sources, their fitness may be reduced. Understanding how much harbor porpoises can eat after a disturbance, and how quickly they can replenish their energy reserves, is important for assessing the significance of disturbances. After fasting for various time periods (2 to 24 h), four captive harbor porpoises, housed in water and air temperatures similar to those encountered by wild conspecifics, were fed a structured diet of meals larger than usual (each normal meal was 20% of the daily food mass requirement). A few times they were fed ad libitum, but this led to severe constipation, so this feeding method was abandoned for welfare and health reasons. The food ingested over a period of one hour following fasting for 2 to 24 hours was quantified (i.e., mass, volume, and as a percentage of normal daily food mass intake in that period). The results show that, in contrast to established belief, harbor porpoises can eat a large percentage (up to ~98%) of their normal daily food mass intake in a single feeding bout without showing physical problems. Adult animals of around 155 cm in body length can eat up to ~3 kg (~2,700 ml) in one feed. If food is abundantly available after a period of fasting due to a disturbance, wild harbor porpoises could eat a large percentage of their daily energetic requirement in one feeding bout to compensate for the period of fasting. However, if food availability is limited in terms of prey numbers, size, or species, or if the fish are widely dispersed (so that more time is required to find and capture them), this may limit or reduce the speed of the recovery of body mass and blubber layer.

Behavioral Responses of Harbor Porpoises (Phocoena phocoena) to U.S. Navy 53C Sonar Signals in Noise

Behavioral Responses of Harbor Porpoises (Phocoena phocoena) to U.S. Navy 53C Sonar Signals in Noise

The Effects of Visual Impediment on the Approaching Behavior of Harbor Porpoise, Phocoena phocoena

Studies on odontocetes (e.g., porpoises) have revealed that these animals may adaptively use vision. The present study examined the contributions of vision to the approaching behavior of the harbor porpoise (Phocoena phocoena). When a porpoise approached a target, the time-to-contact perceived by the animal and its trajectory with a visual impediment condition were compared with those in the control (no impediment) condition. The results suggested that approaching behavior to a stationary target was guided by the animal's evaluation of time-to-contact (τ), maintaining the time derivative of τ () at a constant value. A porpoise with visual deprivation exhibited grater τ value and a longer evaluation time before contact than a porpoise that was not blindfolded in the task of reaching for the target. Furthermore, the porpoise with a visual impediment changed its swimming trajectory toward a target less than the control, which appeared to adaptively adjust its approaching trajectory. These findings imply that the use of vision aided echolocation and enables precise control and alteration of the trajectory during the approach. The present study has implications for adaptive use of vision during approaching behavior in the harbor porpoise.

The impact of marine vessels on the presence and behaviour of harbour porpoise (Phocoena phocoena) in the waters off Berry Head, Brixham (South West England)

Harbour porpoise (Phocoena phocoena) are protected in the UK by the Wildlife and Countryside Act (1981). Understanding the impact of anthropogenic pressures is fundamental for effective protection under this act and successful conservation generally. Land-based observations (n = 146) were conducted over a three-month period, during which, porpoise presence, behaviour, vessel type, and locations were recorded. A total of 2461 behavioural observations were recorded, along with a total frequency of marine vessels of 1377.Principal Component Analysis (76.44%, p = <0.001) revealed a moderate negative correlation between component one (vessels) and two (porpoises and feeding behaviour) (−0.413), indicating that P. phocoena presence and feeding behaviour reduced in response to increasing vessel frequencies. In addition, P. phocoena were sighted more frequently during periods of rising tide at a 1% significance level, consistent with previous results obtained by other Authors.Using measures outlined by the European Commission, the impacts recorded here make this population of porpoises eligible for possible protection under a Special Area of Conservation or for inclusion within the Torbay Marine Conservation Zone as a “priority species”.

Porpoise click classifier (PorCC): A high-accuracy classifier to study harbour porpoises (Phocoena phocoena) in the wild.

Harbour porpoises are well-suited for passive acoustic monitoring (PAM) as they produce highly stereotyped narrow-band high-frequency (NBHF) echolocation clicks. PAM systems must be coupled with a classification algorithm to identify the signals of interest. Here, the authors present a harbour porpoise click classifier (PorCC) developed in matlab, which uses the coefficients of two logistic regression models in a decision-making pathway to assign candidate signals to one of three categories: high-quality clicks (HQ), low-quality clicks (LQ), or high-frequency noise. The receiver operating characteristics of PorCC was compared to that of PAMGuard's Porpoise Click Detector/Classifier Module. PorCC outperformed PAMGuard's classifier achieving higher hit rates (correctly classified clicks) and lower false alarm levels (noise classified as HQ or LQ clicks). Additionally, the detectability index (d') for HQ clicks for PAMGuard was 2.2 (overall d' = 2.0) versus 4.1 for PorCC (overall d' = 3.4). PorCC classification algorithm is a rapid and highly accurate method to classify NBHF clicks, which could be applied for real time monitoring, as well as to study harbour porpoises, and potentially other NBHF species, throughout their distribution range from data collected using towed hydrophones or static recorders. Moreover, PorCC is suitable for studies of acoustic communication of porpoises.