Harbour porpoise (Phocoena phocoena) echolocation activity related to boat noise and boat presence near the Kullaberg marine reserve in northern Öresund, Sweden
(2021) BIOM02 20211Degree Projects in Biology
- Abstract
- The impacts of harbour porpoises by human-made, so called anthropogenic, underwater noise disturbance have been investigated in the past decades. As harbour porpoises are protected under the EU habitat directive, underwater noise management has been proposed as part of conservation efforts. Disturbance of harbour porpoises by ship noise and boat activity has previously been reported to have negative implications for their fitness. To add to the understanding of the disturbance by motorboats, this study investigated porpoise echolocation activity (as a presence/absence measure) by passive acoustic monitoring (PAM) in response to direct noise effects of passing motorboats and indirect effects by proxies of boat activity, such as weather... (More)
- The impacts of harbour porpoises by human-made, so called anthropogenic, underwater noise disturbance have been investigated in the past decades. As harbour porpoises are protected under the EU habitat directive, underwater noise management has been proposed as part of conservation efforts. Disturbance of harbour porpoises by ship noise and boat activity has previously been reported to have negative implications for their fitness. To add to the understanding of the disturbance by motorboats, this study investigated porpoise echolocation activity (as a presence/absence measure) by passive acoustic monitoring (PAM) in response to direct noise effects of passing motorboats and indirect effects by proxies of boat activity, such as weather conditions, near the Kullaberg marine reserve on the west coast of Sweden. Porpoise echolocation activity recorded by a SoundTrap during one week in June 2020 was negatively related to boat noise measured as root mean square noise level in the third octave of 16 kHz. A substantial decrease of echolocation activity was detected above 90 dB re 1 µPa rms, as well as during noise events with levels above that threshold, that were associated with boat passages, compared to preceding and following minutes. Testing the performance of the detection algorithm indicated that porpoise detection under elevated noise levels was robust. Porpoise echolocation activity detected by a C-POD during one month in summer (June-July 2020) was positively linked to a principal component axis of weather that was highly correlated with wind speed as a proxy for boat activity. Contrastingly, in one month in autumn (October 2020) no such effect was prevalent. The results suggest a reduced activity of harbour porpoises to increased levels of boat noise, as well as a positive influence of unfavourable, i.e. windy and rainy, weather on porpoise activity, proposedly due to decreased boating activity in such conditions. Further studies combining both acoustic and observational monitoring are needed to link boat disturbance more tightly to responses of harbour porpoises. (Less)
- Popular Abstract
- Are harbour porpoises at Kullaberg disturbed by boats?
Human-made underwater noise in the seas can impact marine life in various ways. The harbour porpoise (Phocoena phocoena), a small whale, is sensitive to underwater noise because of its good hearing ability. This is important because it uses echolocation to find food, orientate, and communicate. The marine reserve at Kullaberg on the Swedish west coast has a high density of harbour porpoises, often with sightings of mothers and calves in summer, and simultaneously a high density of recreational boating. Harbour porpoises have previously been shown to be disturbed by noise and presence of vessels. The aim of this project was therefore to investigate if harbour porpoises are disturbed... (More) - Are harbour porpoises at Kullaberg disturbed by boats?
Human-made underwater noise in the seas can impact marine life in various ways. The harbour porpoise (Phocoena phocoena), a small whale, is sensitive to underwater noise because of its good hearing ability. This is important because it uses echolocation to find food, orientate, and communicate. The marine reserve at Kullaberg on the Swedish west coast has a high density of harbour porpoises, often with sightings of mothers and calves in summer, and simultaneously a high density of recreational boating. Harbour porpoises have previously been shown to be disturbed by noise and presence of vessels. The aim of this project was therefore to investigate if harbour porpoises are disturbed by boat activity, in terms of noise and presence, at Kullaberg.
Underwater recordings of noise from boats and of harbour porpoise echolocation of one week in summer (24th – 30th June 2020) were analysed looking at the influence of boat noise on porpoise activity. It was also investigated if noise had an influence on the detection of porpoise echolocation in terms of technical performance. Furthermore, effects of weather (wind, rain, sunshine) and day of the week, as proxies for boat activity, on porpoise echolocation activity were analysed for one month in summer (24th June – 22nd July 2020) and one month in autumn (30th September – 28th October).
Results
With increasing underwater noise levels, the porpoise echolocation activity decreased, especially above a certain noise level. Porpoise activity was also lower during boat passages, that were loosely defined as events with noise levels above a certain threshold, compared to before and after these events. Overall, this suggests that porpoises either echolocated less or left the area in response to the noise and thus were disturbed by it. A technical issue with porpoise detection in higher noise levels was unlikely as shown by performance test.
Harbour porpoise echolocation in summer was positively related to “bad weather”, mainly characterised by higher wind speed, while this was not the case in autumn. The boat intensity is higher in summer than in autumn and higher in “good” than “bad” weather conditions at Kullaberg. Porpoise activity was however not different between workdays and weekends (as proxies for recreational boating intensity). Thus, porpoises probably react positively to a decreased boat intensity under “bad” weather conditions in summer while the effect might be missing in autumn because of an overall low boat intensity. Including direct boat observations could have supported this suggested link.
Concluding remarks
The impacts of boat disturbance on the porpoise population at Kullaberg needs to be investigated further. Nevertheless, noise disturbance from boats can have negative effects on porpoises. As a precaution further measures to decrease underwater noise from boats near the marine reserve should be taken, since recreational boating and important porpoise habitats overlap at Kullaberg.
Master’s Degree Project in Biology with specialisation in Aquatic Ecology, 30 credits, 2021
Department of Biology, Lund University
Advisors: Johanna Stedt, Magnus Wahlberg, Per Carlsson, Anders Nilsson
Aquatic Ecology, Department of Biology (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9069221
- author
- Bachmann, Pia Louise
- supervisor
- organization
- course
- BIOM02 20211
- year
- 2021
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9069221
- date added to LUP
- 2021-12-17 10:40:58
- date last changed
- 2021-12-17 10:40:58
@misc{9069221,
abstract = {{The impacts of harbour porpoises by human-made, so called anthropogenic, underwater noise disturbance have been investigated in the past decades. As harbour porpoises are protected under the EU habitat directive, underwater noise management has been proposed as part of conservation efforts. Disturbance of harbour porpoises by ship noise and boat activity has previously been reported to have negative implications for their fitness. To add to the understanding of the disturbance by motorboats, this study investigated porpoise echolocation activity (as a presence/absence measure) by passive acoustic monitoring (PAM) in response to direct noise effects of passing motorboats and indirect effects by proxies of boat activity, such as weather conditions, near the Kullaberg marine reserve on the west coast of Sweden. Porpoise echolocation activity recorded by a SoundTrap during one week in June 2020 was negatively related to boat noise measured as root mean square noise level in the third octave of 16 kHz. A substantial decrease of echolocation activity was detected above 90 dB re 1 µPa rms, as well as during noise events with levels above that threshold, that were associated with boat passages, compared to preceding and following minutes. Testing the performance of the detection algorithm indicated that porpoise detection under elevated noise levels was robust. Porpoise echolocation activity detected by a C-POD during one month in summer (June-July 2020) was positively linked to a principal component axis of weather that was highly correlated with wind speed as a proxy for boat activity. Contrastingly, in one month in autumn (October 2020) no such effect was prevalent. The results suggest a reduced activity of harbour porpoises to increased levels of boat noise, as well as a positive influence of unfavourable, i.e. windy and rainy, weather on porpoise activity, proposedly due to decreased boating activity in such conditions. Further studies combining both acoustic and observational monitoring are needed to link boat disturbance more tightly to responses of harbour porpoises.}},
author = {{Bachmann, Pia Louise}},
language = {{eng}},
note = {{Student Paper}},
title = {{Harbour porpoise (Phocoena phocoena) echolocation activity related to boat noise and boat presence near the Kullaberg marine reserve in northern Öresund, Sweden}},
year = {{2021}},
}