Phocoena Phocoena Research Articles

Large-scale static acoustic survey of a low-density population—Estimating the abundance of the Baltic Sea harbor porpoise

SAMBAH (Static Acoustic Monitoring of the Baltic Sea Harbor Porpoise) is an EU LIFE + -funded project with the primary goal of estimating the abundance and distribution of the critically endangered Baltic Sea harbor porpoise. From May 2011 to April 2013, project members in all EU countries around the Baltic Sea undertook a static acoustic survey using 304 porpoise detectors distributed in a randomly positioned systematic grid in waters 5–80 m deep. In the recorded data, click trains originating from porpoises have been identified automatically using an algorithm developed specifically for Baltic conditions. To determine the click train C-POD detection function, a series of experiments have been carried out, including acoustic tracking of wild free ranging porpoises using hydrophone arrays in an area with moored C-PODs and playbacks of porpoise-like signals at SAMBAH C-PODs during various hydrological conditions. Porpoise abundance has been estimated by counting the number of individuals detected in short time interval windows (snapshots), and then accounting for false positive detections, probability of animals being silent, and probability of detection of non-silent animals within a specified maximum range. We describe the method in detail, and how the auxiliary experiments have enabled us to estimate the required quantities.

Effect of Series of 1 to 2 kHz and 6 to 7 kHz Up-Sweeps and Down-Sweeps on the Behavior of a Harbor Porpoise (Phocoena phocoena)

To compare the effect of naval sonar up-sweeps and down-sweeps on the behavior of harbor porpoises, a harbor porpoise in a large pool was exposed to simulated low- and mid-frequency active sonar signals (series of 1-s duration frequency-modulated sweeps). Three sweep pairs were tested: (1) a 1 to 2 kHz up-sweep was compared with a 2 to 1 kHz down-sweep (both without harmonics) at a mean received sound pressure level (mean received SPL) of 114 dB re 1 µPa; (2) a 1 to 2 kHz up-sweep was compared with a 2 to 1 kHz downsweep (both with harmonics; mean received SPL: 123 dB re 1 µPa); and (3) a 6 to 7 kHz up-sweep was compared with a 7 to 6 kHz down-sweep (both without harmonics; mean SPL: 107 dB re 1 µPa). For each sweep pair, the level was chosen during a pretest session with the intention that the harbor porpoise would respond to the sounds by moving away from the projector and surfacing more often (i.e., he would show a change in behavior). The study consists of three separate parts, so only a comparison within sweep pairs could be made and not between sweep pairs. For the 1 to 2 kHz sweeps with harmonics, the harbor porpoise swam further away from the sound source in response to the up-sweeps than to the downsweeps. For the other two sweep pairs, sweep type (up-sweep or down-sweep) caused no significant difference in the harbor porpoise’s response. Thus, to allow the evaluation of potential effects of sonar sounds on harbor porpoises, sonar signal measurements should include the harmonics. For simulated naval sonar sounds with fundamental frequencies in the 1 to 2 kHz range containing harmonics, using down-sweeps appears to affect harbor porpoise behavior less than using up-sweeps.

Frequency of greatest temporary hearing threshold shift in harbor porpoises (Phocoena phocoena) depends on the noise level.

Harbor porpoises may suffer hearing loss when they are exposed to high level sounds. After exposure for 60 min to a 6.5 kHz continuous tone at average received sound pressure levels (SPLav.re.) ranging from 118 to 154 dB re 1μPa, the temporary hearing threshold shifts (TTSs) of a harbor porpoise were quantified at the center frequency (6.5 kHz), at 0.5, 1.0, and 1.3 octaves above the center frequency (9.2, 13.0, and 16.0 kHz), and at a frequency assumed to be ecologically important for harbor porpoises (125 kHz, the center frequency of their echolocation signals) by means of a psychoacoustic technique. The hearing frequency at which the maximum TTS occurred depended on the SPLav.re. The higher the SPLav.re., the higher the TTS induced at frequencies higher than the exposure frequency; below 148 dB re 1 μPa, the maximum TTS was at 6.5 kHz, whereas above 148 dB re 1 μPa, the maximum TTS was at 9.2 kHz. The hearing threshold of the harbor porpoise for the center frequency of its echolocation signals (125 kHz) was not affected at the highest SPLav.re. to which the animal was exposed.

Harbour porpoises (Phocoena phocoena) stranded along the southern North Sea: An assessment through metallic contamination

Throughout the last few years, the southern North Sea has witnessed an increase in the number of stranded marine mammals, particularly the harbour porpoise (Phocoena phocoena). This species is subject to several potential threats such as exposure to contaminants, changes in food supply, marine traffic and fishery by-catch. The aims of this study were to investigate potential associations between contaminants and health status and to analyze spatial and temporal trends of metal concentrations in harbour porpoises. Selected trace elements (As, Cd, Cr, Cu, Hg, Mn, Se, V and Zn) were measured in kidneys and livers of 105 harbour porpoises stranded along the southern North Sea (French and Belgian coasts from 2006 to 2013) and 27 stranded along the Bay of Biscay (French coast from 2009 to 2012). Porpoises that died from infectious disease displayed significant higher hepatic concentrations of Cd, Hg, Se and Zn compared to healthy porpoises that died from physical trauma. Adult porpoises displayed significant higher concentrations of Cd, Cr, Hg, Se and V in livers compared to juveniles. No spatial or temporal trends in metal concentrations were detected in our study. The results of the present study suggested that chemical contamination may represent one of many threats encountered by harbour porpoises, but it cannot explain alone the increase in the number of stranded individuals.

Cetacean occurrence, habitat preferences and potential for cetacean–fishery interactions in Iberian Atlantic waters: results from cooperative research involving local stakeholders

Abstract Iberian Atlantic waters are heavily exploited by Spanish and Portuguese fisheries. Overlaps between fishery target species and cetacean diet, and between fishing grounds and cetacean foraging areas, can lead to cetacean–fishery interactions including bycatch mortality of cetaceans. The present study assesses cetacean distribution, habitat preferences and hotspots for cetacean–fishery interactions by using a cooperative research approach with stakeholder participation (fishers, fisheries observers, fisheries authorities, scientists), as well as the combination of different opportunistic data sources (interviews, on‐board observations). The usefulness of each data type is evaluated. The implications of results for the monitoring and mitigation of cetacean–fishery interactions are discussed. Generalized linear models and GIS maps were used to relate cetacean occurrence patterns to environmental variables (geographic area, water depth, coastal morphology) and to fishing activities (fishing grounds, fisheries target species). Common and bottlenose dolphins were the most frequently sighted species, the former in waters >50 m, frequently from purse seiners and trawlers, and the latter particularly inside the south Galician rías and close to vessels operating further offshore in Portuguese waters. Harbour porpoises were seen over the whole continental shelf, often next to beach seines, while long‐finned pilot whales and striped dolphins were mostly seen from vessels fishing offshore. Results suggest that cetacean occurrence is linked to prey distribution and that interactions with fisheries are most likely for common dolphins (with coastal purse seines and offshore trawls), bottlenose dolphins and harbour porpoises (coastal nets). The different data sources were complementary and provided results broadly consistent with previous studies on cetacean occurrence in the same area, although sightings frequency for some cetacean species was biased by survey method. Opportunistic sampling has certain restrictions concerning reliability, but can cover a wide area at comparatively low cost and make use of local ecological knowledge to yield information required for cetacean conservation. Copyright © 2014 John Wiley & Sons, Ltd.

Measuring the Economic Value of Increased Precision in Scientific Estimates of Marine Mammal Abundance and Bycatch: Harbor Porpoise Phocoena phocoena in the Northeast U.S. Gill‐Net Fishery

AbstractMarine mammal stock assessments provide information that is valuable to public sector management and the private fishing sector; however, data are costly to collect. The precautionary approach, which is widely used in fishery and marine mammal management, advocates a conservative management decision with priority to the resource when there is uncertainty regarding the impact on the resource from human activity. The potential biological removal (PBR) control rule of the U.S. Marine Mammal Protection Act explicitly incorporates uncertainty in input variables into the determination of allowable levels of human‐induced mortality for a stock. Less uncertainty results in higher PBR values for a given stock level. Variations in government funding levels can disrupt the scientific data collection that is necessary for PBR calculation. We present an economic net benefit framework that examines the indirect value of information from marine mammal stock assessments to the commercial fishing industry. Using the harbor porpoise Phocoena phocoena and the U.S. Atlantic sink gill‐net fishery as a case study, we estimated the difference between total public sector data collection costs and total private sector benefits from increased profits. Net benefits represent a measure of the value of information to society, while the difference in profits measures the value of the information to the private sector. Several results are forthcoming. First, the optimal allocation of funding showed that abundance surveys are a more cost‐effective means to reduce uncertainty in PBR input variables than increasing observer coverage of the fishing industry. Second, for all levels of PBR in this empirical example, total benefits to the private sector for a higher PBR exceeded the costs of collecting additional scientific data to increase the precision of input variables and thus increase PBR. Since net benefits are positive, the private sector may consider funding of scientific data collection for marine mammals as a way to reduce uncertainty, thereby allowing a higher PBR value.Received March 19, 2013; accepted November 14, 2013

No Serological Evidence that Harbour Porpoises Are Additional Hosts of Influenza B Viruses

Influenza A and B viruses circulate among humans causing epidemics almost annually. While various hosts for influenza A viruses exist, influenza B viruses have been detected only in humans and seals. However, recurrent infections of seals in Dutch coastal waters with influenza B viruses that are antigenetically distinct from influenza B viruses circulating among humans suggest that influenza B viruses have been introduced into this seal population by another, non-human, host. Harbour porpoises (Phocoena phocoena) are sympatric with seals in these waters and are also occasionally in close contact with humans after stranding and subsequent rehabilitation. In addition, virus attachment studies demonstrated that influenza B viruses can bind to cells of the respiratory tract of these animals. Therefore, we hypothesized that harbour porpoises might be a reservoir of influenza B viruses. In the present study, an unique set of serum samples from 79 harbour porpoises, stranded alive on the Dutch coast between 2003 and 2013, was tested for the presence of antibodies against influenza B viruses by use of the hemagglutination inhibition test and for antibodies against influenza A viruses by use of a competitive influenza A nucleoprotein ELISA. No antibodies were detected against either virus, suggesting that influenza A and B virus infections of harbour porpoises in Dutch coastal waters are not common, which was supported by statistical analysis of the dataset.

Direct evidence for gray seal (Halichoerus grypus) predation and scavenging on harbor porpoises (Phocoena phocoena)

THIBAUT BOUVEROUX, Observatoire pour la Conservation et l’Etude des Animaux et Milieux Marins (OCEAMM), 51 Rue du G en eral de Gaulle, F-59123 Zuydcoote, France; JEREMY J. KISZKA andMICHAEL R. HEITHAUS, Marine Sciences Program, Department of Biological Sciences, Florida International University, 3000 NE 151st Street, North Miami, Florida 33181, U.S.A.; THIERRY JAUNIAUX, Department of Veterinary Pathology, Sart Tilman, University of Li ege, B-4000, Belgium; SYLVAIN PEZERIL, Observatoire pour la Conservation et l’Etude des Animaux et Milieux Marins (OCEAMM), 51 Rue du G en eral de Gaulle, F-59123 Zuydcoote, France.

Correction: The Stranding Anomaly as Population Indicator: The Case of Harbour Porpoise Phocoena phocoena in North-Western Europe

Correction: The Stranding Anomaly as Population Indicator: The Case of Harbour Porpoise Phocoena phocoena in North-Western Europe

Density Estimates of Harbour Porpoises Phocoena Phocoena at Eight Coastal Sites in Ireland

Single platform line-transect surveys with distance sampling were carried out at eight sites between July and September 2008 to derive density and abundance estimates of harbour porpoises. Over 37 days at sea, a total of 475 track-lines were surveyed for a total distance of 20,623km. From the 332 sightings, a total of 618 individual harbour porpoise were recorded. Overall density estimates ranged from 0.53 to 2.03 porpoises km−2 (without correction for g(0)). Mean group size varied from 1.41 to 2.67. These data provide baseline information to help identify important habitats for harbour porpoise and reference values for monitoring future changes in harbour porpoise distribution and densities in Ireland.

Using drifting passive echolocation loggers to study harbour porpoises in tidal-stream habitats

Moored passive acoustic detectors (e.g. C-PODs) are widely used to study harbour porpoise Phocoena phocoena distribution and relative abundance, but their use in tidal-stream habitats is complicated by the need for retrievable flow-resistant seabed fixings and the occur- rence of flow-induced noise in the resultant data. In this study, we explored the use of a new method aimed at tidal-stream habitats, which are of increasing interest for marine renewable energy generation. Porpoise detectors (C-PODs) were attached to multiple drifters and repeatedly set adrift at a tidal-stream site in western Scotland during May 2010 and August 2011. Porpoise vocalisations were successfully detected under varying tidal conditions during approximately 63 h of drifting. Harbour porpoise distribution, as determined by the drifting detectors, was similar to that found using the traditional, yet more logistically intensive, visual and acoustic boat-based sur- veys and to an extent that found by moored C-PODs. Drifting detectors also mapped tidally driven spatiotemporal variability in ambient noise levels which could influence porpoise detection. In summary, drifters equipped with passive acoustic detectors offer a new, rapid and inexpensive tool for investigating porpoise occurrence and behaviour in tidal-stream habitats, and should be considered as part of a comprehensive marine mammal monitoring approach of these energetic environments in the context of marine renewable energy development and other industries.

A practical weighting function for harbor porpoise underwater sound level measurements

Harbor porpoise (Phocoena phocoena) are subject to underwater noise disturbance from anthropogenic sources, especially shipping. The underwater audiograms of harbor porpoise were used to create a frequency weighting function, dBht(Phocoena phocoena), to permit estimation of the broadband perceived amplitudes of ambient and shipping noise. An equation was fit to the 0.02-20 kHz range of unmasked detection thresholds and normalizing to 0 dB at 20 kHz; dB = 46.4-35.6 log(kHz). The weighting function de-emphasizes the low frequency components of noise. Harbor porpoise hearing is less sensitive to low frequency shipping noise and, except at high amplitudes, estimating potential noise impacts using linear measurements will be misleading.

Hearing frequency thresholds of a harbor porpoise (Phocoena phocoena) temporarily affected by a continuous 1.5 kHz tone

Harbor porpoises may suffer hearing loss when exposed to intense sounds. After exposure to a 1.5 kHz continuous tone without harmonics at a mean received sound pressure level of 154 dB re 1 μPa for 60 min (cumulative sound exposure level: 190 dB re 1 μPa(2) s), the temporary hearing threshold shift (TTS) of a porpoise was quantified at 1.5, 2, 4, 6.5, 8, 16, 32, 63, and 125 kHz with a psychoacoustic technique. Significant TTS only occurred at 1.5 and 2 kHz. Mean TTS (1-4 min after sound exposure stopped) was ~14 dB at 1.5 kHz and ~11 dB at 2 kHz, and recovery occurred within 96 min. Control hearing tests before and after a 60 min low ambient noise exposure showed that normal variation in TTS was limited (standard deviation: ± 1.0 dB). Ecological effects of TTS depend not only on the magnitude of the TTS, its duration (depending on the exposure duration), and the recovery time after the exposure stopped, but also on the hearing frequency affected by the fatiguing noise. The hearing thresholds of harbor porpoises for the frequencies of their echolocation signals are not affected by intense low frequency sounds, therefore these sounds are unlikely to affect foraging efficiency.

Records of Harbour Porpoises (Phocoena phocoena) in Fishing Nets During the Interwar Period in Poland: Verification of Archival Materials

Records of Harbour Porpoises (Phocoena phocoena) in Fishing Nets During the Interwar Period in Poland: Verification of Archival Materials

Community-Based Observations of Marine Mammal Occurrences in Groswater Bay, Labrador

Experienced observers from the community of Rigolet, Newfoundland and Labrador, recorded marine mammal observations at Rigolet on the coast of Labrador from July to September 2012. During this study, a total of nine species of marine mammals were documented. A daily average of 2.6 (range 1–5) marine mammal species were observed, with Harp Seals (Pagophilus groenlandicus) and Common Minke Whales (Balaenoptera acutorostrata) being the most common. The area is thought to be regionally important for Ringed Seal (Pusa hispida) whelping; however, Ringed Seals were not observed in large numbers. Beluga Whales (Delphinapterus leucas) were also reported anecdotally, but were less common than the other species, with the possible exception of the Harbour Porpoise (Phocoena phocoena). Labrador is experiencing significant industrial growth related to hydroelectric development and offshore oil and gas exploration. These data should aid environmental assessment and environmental effects monitoring and assist researchers in understanding regional marine mammal ecology, including species diversity, seasonal occurrence, and relative abundance.

Identifying Foraging Behaviour of Wild Bottlenose Dolphins (Tursiops truncatus) and Harbour Porpoises (Phocoena phocoena) with Static Acoustic Dataloggers

Sound is the main means of communication for cetaceans, and studying their vocal behaviour can reveal important information about their activity patterns. As static acoustic monitoring (SAM) of whales, dolphins, and porpoises becomes more widespread, it is important to understand how data collected with automated click loggers relate to their behaviour. To assess whether behaviour can be inferred from automated click train data, echolocation click trains (series of clicks) of bottlenose dolphins and harbour porpoises recorded by C PODs were examined with simultaneous visual observations. Recorded click trains from both species had different characteristics for the two observed behavioural categories: (1) travelling and (2) foraging. Foraging click trains for both species were of shorter duration and had shorter inter-click intervals. The distinction in the click trains between the two behaviours was stronger for harbour porpoises. More than one quarter of the harbour porpoise click trains represented a distinct group of very fast click trains or “buzzes,” which were thought to be associated with foraging, whereas only a small fraction of such trains was found in the bottlenose dolphin click data. For both species, the C PODs showed potential in detecting foraging behaviour and in identifying potential feeding sites and trends in foraging activity.

Brief Behavioral Response Threshold Levels of a Harbor Porpoise (Phocoena phocoena) to Five Helicopter Dipping Sonar Signals (1.33 to 1.43 kHz)

Brief Behavioral Response Threshold Levels of a Harbor Porpoise (Phocoena phocoena) to Five Helicopter Dipping Sonar Signals (1.33 to 1.43 kHz)

Analysis of harbor porpoise gillnet bycatch, compliance, and enforcement trends in the US northwestern Atlantic, January 1999 to May 2010

In 1999 the US National Marine Fisheries Service (NMFS) implemented regulations to limit harbor porpoise Phocoena phocoena incidental bycatch in US waters of the northwestern Atlantic. This effort was called the Harbor Porpoise Take Reduction Plan (HPTRP) and included a mixture of time-area closures, pinger and other gear modification requirements, a pinger training program, and outreach and education efforts. This paper focuses on the plan from January 1999 to May 2010 and examines trends in bycatch patterns, compliance with the plan, enforcement of the plan requirements, and changes in the primary fisheries involved in harbor porpoise bycatch. Over the course of the plan harbor porpoise bycatch dropped in the first few years, increased to unacceptable levels during the middle years, and moderated in the later years of the plan. Changes in fishing effort and distribution of key fisheries played a large role in decreasing the bycatch in much of the Mid-Atlantic and also in increasing bycatch in Southern New England and off the coast of New Jersey. The pattern in compliance levels had an inverse relationship with bycatch levels, with better compliance and lower bycatch in early and late years, though compli- ance was generally poor even when at its best. Enforcement of HPTRP regulations was not well documented, but, from available compliance data, it appears that what enforcement did occur was not sufficient to improve compliance. Given poor compliance with pinger requirements, these requirements have not resulted in the expected reduction in bycatch.

Harbour porpoises (Phocoena phocoena) and minke whales (Balaenoptera acutorostrata) observed during land-based surveys in The Minch, north-west Scotland

The waters off north-west Scotland are known to provide important habitat for the harbour porpoise (Phocoena phocoena) and the minke whale (Balaenoptera acutorostrata). Between October 2008 and April 2011, systematic land-based surveys were carried out to assess the seasonal occurrence, group size and group behaviours of both species in a study area located off Melvaig, near Gairloch. Data were collected on 47 separate days, with a total of 4543 minutes of survey effort (in sea states ≤3) recorded during the spring months and 8204 minutes of effort during the autumn. A total of 189 sightings of marine fauna were recorded, comprising 126 cetacean sightings, 50 seal sightings and 13 sightings of basking sharks (Cetorhinus maximus). Six species of cetacean were identified, with most sightings comprising harbour porpoise (N = 72) or minke whale (N = 38). Harbour porpoise abundance was higher in autumn than in spring and there was a variation between years in numbers of minke whales sighted. In porpoises, sea state and cloud cover both influenced sightings and increasing sea state influenced survey area. Foraging behaviour was exhibited in 13% of harbour porpoise sightings and 34% of minke whale sightings. Results demonstrate a regular occurrence of harbour porpoises and minke whales in nearshore waters off Gairloch. Densities are comparable to boat surveys in the region and so support the use of land-based watches as a potential longer-term monitoring method for these species in coastal waters. Given the regular use of this area by these two European Protected Species, as well as the occurrence of a range of human activities potentially affecting them in the region, it may be appropriate to consider protecting this area for their conservation.

The Stranding Anomaly as Population Indicator: The Case of Harbour Porpoise Phocoena phocoena in North-Western Europe

Ecological indicators for monitoring strategies are expected to combine three major characteristics: ecological significance, statistical credibility, and cost-effectiveness. Strategies based on stranding networks rank highly in cost-effectiveness, but their ecological significance and statistical credibility are disputed. Our present goal is to improve the value of stranding data as population indicator as part of monitoring strategies by constructing the spatial and temporal null hypothesis for strandings. The null hypothesis is defined as: small cetacean distribution and mortality are uniform in space and constant in time. We used a drift model to map stranding probabilities and predict stranding patterns of cetacean carcasses under H0 across the North Sea, the Channel and the Bay of Biscay, for the period 1990–2009. As the most common cetacean occurring in this area, we chose the harbour porpoise Phocoena phocoena for our modelling. The difference between these strandings expected under H0 and observed strandings is defined as the stranding anomaly. It constituted the stranding data series corrected for drift conditions. Seasonal decomposition of stranding anomaly suggested that drift conditions did not explain observed seasonal variations of porpoise strandings. Long-term stranding anomalies increased first in the southern North Sea, the Channel and Bay of Biscay coasts, and finally the eastern North Sea. The hypothesis of changes in porpoise distribution was consistent with local visual surveys, mostly SCANS surveys (1994 and 2005). This new indicator could be applied to cetacean populations across the world and more widely to marine megafauna.