The Journal of the Acoustical Society of America, 2015
Sei whale calls have been documented on very few occasions and never in the Azores Archipelago, a... more Sei whale calls have been documented on very few occasions and never in the Azores Archipelago, an area transited by this species during their migration to northern latitudes in spring and early summer. Using a combination of video range tracking (VRT) and acoustic methods, vocalizations are described from an encounter with two sei whales in April 2012 off Pico Island, Azores. Recordings analyzed post-survey revealed 53 low frequency downsweep calls with average maximum frequencies of 100 Hz [standard deviation (SD = 14 Hz)] down to 37 Hz (SD = 8 Hz) over 1.21 s (SD = 0.33 s). Apparent source levels of 177 dB (SD = 5 dB) root-mean-square (rms) re 1 μPa were recorded. Vocalizations were attributed to the pair of sei whales encountered using a combination of the VRT data and differences in arrival time of calls at the hydrophones. These calls are similar to those reported from sei whales off New England and similar to those recorded off Hawaii. The growing body of acoustic data on sei...
Boat-based acoustic and visual surveys for harbour porpoises (Phocoena phocoena) were conducted d... more Boat-based acoustic and visual surveys for harbour porpoises (Phocoena phocoena) were conducted during the summers of 2001 and 2002 in order to investigate their distribution and relative abundance in the Baltic Sea, and to compare the results with the adjacent Kiel and Mecklenburg Bights and the Little Belt. Harbour porpoises are subject to year-round bycatch in gillnets and other fishing gear in these waters. This is of particular concern in the Baltic Sea where a survey carried out in 1995 indicated that the population is low and current levels of anthropogenic mortality are believed to be unsustainable. Polish coastal waters were not included in the 1995 survey and it has been hypothesised that these unsurveyed waters may contain a significant uncounted part of the Baltic Sea population. Results show that the porpoise detection rate was two orders of magnitude lower in the Baltic Sea than in other waters surveyed. No evidence was found that Polish waters contain a significant, p...
The Mediterranean sub-population of sperm whales is believed to be isolated and is classified as ... more The Mediterranean sub-population of sperm whales is believed to be isolated and is classified as Endangered on the IUCN Red List. Although there is evidence to suggest the population is declining, there is a lack of abundance data. A series of acoustic line-transect surveys were undertaken between 2004 and 2013. In 2004, 3,946km of acoustic effort was conducted in the southern Western Mediterranean basin, resulting in the detection of 159 sperm whales. While in 2007 and 2013, 10,276km of acoustic effort was conducted in the Eastern Mediterranean basin, resulting in the detection of 24 sperm whales. A pooled detection function gave an effective strip half-width of 9.8km. A correction for availability bias was made for each block based on published simulations using data on sperm whale acoustic behaviour: estimates of g(0) were 0.95–0.96. Estimated abundances were: Southern Western Mediterranean Block 634 animals [374–1,077] (95% log-normal confidence interval); Hellenic Trench Block ...
Journal of the Marine Biological Association of the United Kingdom, 2007
Acoustic surveys for sperm whales, using line-transect methodology, were carried out in the Ionia... more Acoustic surveys for sperm whales, using line-transect methodology, were carried out in the Ionian Sea and Straits of Sicily, Mediterranean Sea, in 2003. A total of 17 whales were detected along 3846 km of designed survey track in the Ionian Sea, and no whales along 892 km in the Straits of Sicily. This total was insufficient to estimate a detection function, so further data were obtained from quasi-random passages made elsewhere in the western Mediterranean in the same year. The encounters included several tight aggregations with inter-animal spacing less than 1 km, primarily from the western Mediterranean. Including individuals from these aggregations distorted the detection function due to the small sample sizes. No such aggregations were found during formal survey of the two areas of interest, and the aggregations were therefore excluded from detection function estimation. The resultant effective strip half-width was 10.0 km (n=40). On the assumption that g(0)=1, the resulting a...
This study documents the presence of harbour porpoise (Phocoena phocoena, Linnaeus 1758) in the t... more This study documents the presence of harbour porpoise (Phocoena phocoena, Linnaeus 1758) in the tidal Thames from strandings, dedicated surveys and opportunistic sightings. In March 2015, a visual and acoustic vessel survey for harbour porpoises was conducted; 17 sightings and 45 acoustic detections of porpoise groups were documented. A conservative acoustic encounter rate of 4.2 animals/100 km surveyed is estimated, comparable to results from acoustic surveys in other important European porpoise habitats. Presented with data from opportunistic sightings records, porpoises are reported in the tidal Thames during all months, with peak presence in spring and late summer. Results support the need for further studies in this significant habitat, and that harbour porpoises must be considered when planning future activities and developments
The Journal of the Acoustical Society of America, 2015
Sei whale calls have been documented on very few occasions and never in the Azores Archipelago, a... more Sei whale calls have been documented on very few occasions and never in the Azores Archipelago, an area transited by this species during their migration to northern latitudes in spring and early summer. Using a combination of video range tracking (VRT) and acoustic methods, vocalizations are described from an encounter with two sei whales in April 2012 off Pico Island, Azores. Recordings analyzed post-survey revealed 53 low frequency downsweep calls with average maximum frequencies of 100 Hz [standard deviation (SD = 14 Hz)] down to 37 Hz (SD = 8 Hz) over 1.21 s (SD = 0.33 s). Apparent source levels of 177 dB (SD = 5 dB) root-mean-square (rms) re 1 μPa were recorded. Vocalizations were attributed to the pair of sei whales encountered using a combination of the VRT data and differences in arrival time of calls at the hydrophones. These calls are similar to those reported from sei whales off New England and similar to those recorded off Hawaii. The growing body of acoustic data on sei...
Boat-based acoustic and visual surveys for harbour porpoises (Phocoena phocoena) were conducted d... more Boat-based acoustic and visual surveys for harbour porpoises (Phocoena phocoena) were conducted during the summers of 2001 and 2002 in order to investigate their distribution and relative abundance in the Baltic Sea, and to compare the results with the adjacent Kiel and Mecklenburg Bights and the Little Belt. Harbour porpoises are subject to year-round bycatch in gillnets and other fishing gear in these waters. This is of particular concern in the Baltic Sea where a survey carried out in 1995 indicated that the population is low and current levels of anthropogenic mortality are believed to be unsustainable. Polish coastal waters were not included in the 1995 survey and it has been hypothesised that these unsurveyed waters may contain a significant uncounted part of the Baltic Sea population. Results show that the porpoise detection rate was two orders of magnitude lower in the Baltic Sea than in other waters surveyed. No evidence was found that Polish waters contain a significant, p...
The Mediterranean sub-population of sperm whales is believed to be isolated and is classified as ... more The Mediterranean sub-population of sperm whales is believed to be isolated and is classified as Endangered on the IUCN Red List. Although there is evidence to suggest the population is declining, there is a lack of abundance data. A series of acoustic line-transect surveys were undertaken between 2004 and 2013. In 2004, 3,946km of acoustic effort was conducted in the southern Western Mediterranean basin, resulting in the detection of 159 sperm whales. While in 2007 and 2013, 10,276km of acoustic effort was conducted in the Eastern Mediterranean basin, resulting in the detection of 24 sperm whales. A pooled detection function gave an effective strip half-width of 9.8km. A correction for availability bias was made for each block based on published simulations using data on sperm whale acoustic behaviour: estimates of g(0) were 0.95–0.96. Estimated abundances were: Southern Western Mediterranean Block 634 animals [374–1,077] (95% log-normal confidence interval); Hellenic Trench Block ...
Journal of the Marine Biological Association of the United Kingdom, 2007
Acoustic surveys for sperm whales, using line-transect methodology, were carried out in the Ionia... more Acoustic surveys for sperm whales, using line-transect methodology, were carried out in the Ionian Sea and Straits of Sicily, Mediterranean Sea, in 2003. A total of 17 whales were detected along 3846 km of designed survey track in the Ionian Sea, and no whales along 892 km in the Straits of Sicily. This total was insufficient to estimate a detection function, so further data were obtained from quasi-random passages made elsewhere in the western Mediterranean in the same year. The encounters included several tight aggregations with inter-animal spacing less than 1 km, primarily from the western Mediterranean. Including individuals from these aggregations distorted the detection function due to the small sample sizes. No such aggregations were found during formal survey of the two areas of interest, and the aggregations were therefore excluded from detection function estimation. The resultant effective strip half-width was 10.0 km (n=40). On the assumption that g(0)=1, the resulting a...
This study documents the presence of harbour porpoise (Phocoena phocoena, Linnaeus 1758) in the t... more This study documents the presence of harbour porpoise (Phocoena phocoena, Linnaeus 1758) in the tidal Thames from strandings, dedicated surveys and opportunistic sightings. In March 2015, a visual and acoustic vessel survey for harbour porpoises was conducted; 17 sightings and 45 acoustic detections of porpoise groups were documented. A conservative acoustic encounter rate of 4.2 animals/100 km surveyed is estimated, comparable to results from acoustic surveys in other important European porpoise habitats. Presented with data from opportunistic sightings records, porpoises are reported in the tidal Thames during all months, with peak presence in spring and late summer. Results support the need for further studies in this significant habitat, and that harbour porpoises must be considered when planning future activities and developments
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