The habitat of the resident bottlenose dolphins (Tursiops truncatus) of the Cres-Lošinj archipela... more The habitat of the resident bottlenose dolphins (Tursiops truncatus) of the Cres-Lošinj archipelago overlaps with routes of intense boat traffic. Within these waters, Sea Ambient Noise (SAN) was sampled across ten acoustic stations between 2007 and 2009. Data on boat presence was concurrently collected and when dolphins were sighted group behaviour was also recorded. Acoustic recordings were analysed for 1/3 octave bands. Samples containing dolphin whistles were analysed and compared with boat presence and SAN levels. Results indicate that dolphins whistle at higher frequencies in conditions of elevated low frequency noise. Conversely, they reduce maximum, delta and start frequencies and frequency modulations when noise levels increase significantly across higher frequencies. The study shows that high levels of SAN causes significant changes in the acoustic structure of dolphin whistles. Additionally, changes in whistle parameters, in the presence of boats, appear to be related to the behavioural state of the dolphin group.
Abstract: L'area marina protetta di Lussino, istituita nell'estate del 2006, è un'imp... more Abstract: L'area marina protetta di Lussino, istituita nell'estate del 2006, è un'importante area dell'Adriatico settentrionale (Quarnerolo) in quanto ospita una popolazione locale residente di tursiopi (Tursiops truncatus). Tuttavia quest'area è caratterizzata anche da un forte ...
The striped dolphin (Stenella coeruleoalba) is not a common cetacean species in the northern Adri... more The striped dolphin (Stenella coeruleoalba) is not a common cetacean species in the northern Adriatic Sea. Its presence is generally related to deeper offshore areas beyond the continental shelf. Despite this fact, the analysis of data collected over the past 5 years indicates unusual site fidelity of a single individual in the relatively shallow Vinodol Channel of the northern Croatian Adriatic Sea. Summarizing the available data on its recent occurrence, this paper contributes to the current limited knowledge on striped dolphin presence and associations not only in this region.
The Marine Strategy Framework Directive (MSFD), formally adopted by the European Union in July 20... more The Marine Strategy Framework Directive (MSFD), formally adopted by the European Union in July 2008, outlines 11 high level descriptors of Good Environmental Status (GES); descriptor 11 requires "monitoring the introduction of energy, including underwater noise” into the marine environment. A 3-year study monitoring sea ambient noise (SAN) (2007–2009) was carried out in the Cres–Lošinj archipelago, where local dolphin and fish communities are threatened by unregulated mass tourism and coastal construction. The survey was run monthly on ten predefined acoustic stations, grouped into three areas of different anthropogenic impact. A total of 418 five minute SAN samples (frequency range: 25 - 40000 Hz) were collected and analyzed. In the light of Indicator 11.2.1 of the MSFD “Continuous low frequency sound”, the 1/3 octave bands of 63 Hz and 125 Hz (re 1uPa RMS) were considered. During recordings the presence of leisure boats within 2 km of the sampling station and the bottlenose d...
Aquatic Conservation: Marine and Freshwater Ecosystems, 2013
1. Habitat diversity plays a significant role in shaping the genetic structure of cetacean popula... more 1. Habitat diversity plays a significant role in shaping the genetic structure of cetacean populations. However, the processes involved in defining the genetic differentiation of these highly mobile marine mammals are still largely unknown.
Journal of the Marine Biological Association of the United Kingdom, 2013
This study monitors the spatial and temporal variability of sea ambient noise (SAN) in the Cres-L... more This study monitors the spatial and temporal variability of sea ambient noise (SAN) in the Cres-Lošinj archipelago from 2007 to 2009 (north-eastern Adriatic Sea, Croatia). The archipelago is an important marine habitat for many protected species, including the bottlenose dolphin (Tursiops truncatus) that is considered as vulnerable to disturbance from intense local vessel traffic. Systematic monthly sampling of SAN was carried out at ten predefined acoustic stations. Data on the presence, type and distance of vessels from these stations was also collected during sampling and vessels were allocated into four main classes. A sample of noise produced by a representative vessel of each vessel class was collected and the noise levels were extracted on the 1/3 octave band standard centre frequencies. All the recordings were analysed in terms of instantaneous sound pressure level (L LSP , L-weighted, 63 Hz -20 kHz, root mean square fast). The equivalent continuous sound pressure levels (L Leq ) for vessel and SAN were calculated averaging the L LSP of vessel and SAN samples. Results indicate an increase of SAN levels particularly in the range of low frequencies (63 Hz-1 kHz) during the tourist season. A positive relationship was found between the spatial and temporal distribution of SAN and seasonal changes in anthropogenic pressure, in terms of vessel traffic. Potential implications for local marine life, with particular reference to bottlenose dolphins, are discussed.
The Journal of the Acoustical Society of America, 2013
This study aims to provide an objective mapping of the underwater noise and its sources over an A... more This study aims to provide an objective mapping of the underwater noise and its sources over an Adriatic coastal marine habitat by applying the self-organizing maps (SOM) method. Systematic sampling of sea ambient noise (SAN) was carried out at ten predefined acoustic stations between 2007 and 2009. Analyses of noise levels were performed for 1/3 octave band standard centered frequencies in terms of instantaneous sound pressure levels averaged over 300 s to calculate the equivalent continuous sound pressure levels. Data on vessels' presence, type, and distance from the monitoring stations were also collected at each acoustic station during the acoustic sampling. Altogether 69 noise surveys were introduced to the SOM predefined 2 Â 2 array. The overall results of the analysis distinguished two dominant underwater soundscapes, associating them mainly to the seasonal changes in the nautical tourism and fishing activities within the study area and to the wind and wave action. The analysis identified recreational vessels as the dominant anthropogenic source of underwater noise, particularly during the tourist season. The method demonstrated to be an efficient tool in predicting the SAN levels based on the vessel distribution, indicating also the possibility of its wider implication for marine conservation.
The striped dolphin (Stenella coeruleoalba) is not a common cetacean species in the northern Adri... more The striped dolphin (Stenella coeruleoalba) is not a common cetacean species in the northern Adriatic Sea. Its presence is generally related to deeper offshore areas beyond the continental shelf. Despite this fact, the analysis of data collected over the past 5 years indicates unusual site fidelity of a single individual in the relatively shallow Vinodol Channel of the northern Croatian Adriatic Sea. Summarizing the available data on its recent occurrence, this paper contributes to the current limited knowledge on striped dolphin presence and associations not only in this region. Prugasti dupin (Stenella coeruleoalba) ne predstavlja uobi~ajenu vrstu za hrvatski dio sjevernog Jadrana. Obi~no nastanjuje duboka i otvorena mora iza kontinentalnog {elfa. Unato~tome, analiza podataka sakupljenih tijekom proteklih 5 godina ukazuje na neuobi~ajenu privr`enost jedinke prugastog dupina relativno plitkom podru~ju Vinodolskog kanala u hrvatskom dijelu sjevernog Jadrana. Sveukupni podaci o njegovom pojavljivanju predstavljeni su u ovom radu, pridonose}i time dosada{njm ograni~enim saznanjima o prisutnosti prugastih dupina, i to ne samo na ovom podru~ju.
The waters of the Cres-Lošinj archipelago are subject to intense boat traffic related to the high... more The waters of the Cres-Lošinj archipelago are subject to intense boat traffic related to the high number of leisure boats frequenting this area during the summer tourist season. Boat noise dominates the acoustic environment of the local bottlenose dolphin (Tursiops truncatus) population. This study investigates the spatial and temporal change in the underwater noise levels due to intense boating, and its effect on the distribution of the bottlenose dolphins. In the period 2007-2009 sea ambient noise (SAN) was sampled across ten acoustic stations. During data collection the presence of leisure boats was recorded if they were within 2 km of the sampling station. Bottlenose dolphin spatial distribution was monitored in the same period. Results showed a strong positive correlation between high SAN levels and boat presence, particularly in the tourist season. Dolphin distribution indicated significant seasonal displacements from noisy areas characterized by the intense leisure boating.
The habitat of the resident bottlenose dolphins (Tursiops truncatus) of the Cres-Lošinj archipela... more The habitat of the resident bottlenose dolphins (Tursiops truncatus) of the Cres-Lošinj archipelago overlaps with routes of intense boat traffic. Within these waters, Sea Ambient Noise (SAN) was sampled across ten acoustic stations between 2007 and 2009. Data on boat presence was concurrently collected and when dolphins were sighted group behaviour was also recorded. Acoustic recordings were analysed for 1/3 octave bands. Samples containing dolphin whistles were analysed and compared with boat presence and SAN levels. Results indicate that dolphins whistle at higher frequencies in conditions of elevated low frequency noise. Conversely, they reduce maximum, delta and start frequencies and frequency modulations when noise levels increase significantly across higher frequencies. The study shows that high levels of SAN causes significant changes in the acoustic structure of dolphin whistles. Additionally, changes in whistle parameters, in the presence of boats, appear to be related to the behavioural state of the dolphin group.
Abstract: L'area marina protetta di Lussino, istituita nell'estate del 2006, è un'imp... more Abstract: L'area marina protetta di Lussino, istituita nell'estate del 2006, è un'importante area dell'Adriatico settentrionale (Quarnerolo) in quanto ospita una popolazione locale residente di tursiopi (Tursiops truncatus). Tuttavia quest'area è caratterizzata anche da un forte ...
The striped dolphin (Stenella coeruleoalba) is not a common cetacean species in the northern Adri... more The striped dolphin (Stenella coeruleoalba) is not a common cetacean species in the northern Adriatic Sea. Its presence is generally related to deeper offshore areas beyond the continental shelf. Despite this fact, the analysis of data collected over the past 5 years indicates unusual site fidelity of a single individual in the relatively shallow Vinodol Channel of the northern Croatian Adriatic Sea. Summarizing the available data on its recent occurrence, this paper contributes to the current limited knowledge on striped dolphin presence and associations not only in this region.
The Marine Strategy Framework Directive (MSFD), formally adopted by the European Union in July 20... more The Marine Strategy Framework Directive (MSFD), formally adopted by the European Union in July 2008, outlines 11 high level descriptors of Good Environmental Status (GES); descriptor 11 requires "monitoring the introduction of energy, including underwater noise” into the marine environment. A 3-year study monitoring sea ambient noise (SAN) (2007–2009) was carried out in the Cres–Lošinj archipelago, where local dolphin and fish communities are threatened by unregulated mass tourism and coastal construction. The survey was run monthly on ten predefined acoustic stations, grouped into three areas of different anthropogenic impact. A total of 418 five minute SAN samples (frequency range: 25 - 40000 Hz) were collected and analyzed. In the light of Indicator 11.2.1 of the MSFD “Continuous low frequency sound”, the 1/3 octave bands of 63 Hz and 125 Hz (re 1uPa RMS) were considered. During recordings the presence of leisure boats within 2 km of the sampling station and the bottlenose d...
Aquatic Conservation: Marine and Freshwater Ecosystems, 2013
1. Habitat diversity plays a significant role in shaping the genetic structure of cetacean popula... more 1. Habitat diversity plays a significant role in shaping the genetic structure of cetacean populations. However, the processes involved in defining the genetic differentiation of these highly mobile marine mammals are still largely unknown.
Journal of the Marine Biological Association of the United Kingdom, 2013
This study monitors the spatial and temporal variability of sea ambient noise (SAN) in the Cres-L... more This study monitors the spatial and temporal variability of sea ambient noise (SAN) in the Cres-Lošinj archipelago from 2007 to 2009 (north-eastern Adriatic Sea, Croatia). The archipelago is an important marine habitat for many protected species, including the bottlenose dolphin (Tursiops truncatus) that is considered as vulnerable to disturbance from intense local vessel traffic. Systematic monthly sampling of SAN was carried out at ten predefined acoustic stations. Data on the presence, type and distance of vessels from these stations was also collected during sampling and vessels were allocated into four main classes. A sample of noise produced by a representative vessel of each vessel class was collected and the noise levels were extracted on the 1/3 octave band standard centre frequencies. All the recordings were analysed in terms of instantaneous sound pressure level (L LSP , L-weighted, 63 Hz -20 kHz, root mean square fast). The equivalent continuous sound pressure levels (L Leq ) for vessel and SAN were calculated averaging the L LSP of vessel and SAN samples. Results indicate an increase of SAN levels particularly in the range of low frequencies (63 Hz-1 kHz) during the tourist season. A positive relationship was found between the spatial and temporal distribution of SAN and seasonal changes in anthropogenic pressure, in terms of vessel traffic. Potential implications for local marine life, with particular reference to bottlenose dolphins, are discussed.
The Journal of the Acoustical Society of America, 2013
This study aims to provide an objective mapping of the underwater noise and its sources over an A... more This study aims to provide an objective mapping of the underwater noise and its sources over an Adriatic coastal marine habitat by applying the self-organizing maps (SOM) method. Systematic sampling of sea ambient noise (SAN) was carried out at ten predefined acoustic stations between 2007 and 2009. Analyses of noise levels were performed for 1/3 octave band standard centered frequencies in terms of instantaneous sound pressure levels averaged over 300 s to calculate the equivalent continuous sound pressure levels. Data on vessels' presence, type, and distance from the monitoring stations were also collected at each acoustic station during the acoustic sampling. Altogether 69 noise surveys were introduced to the SOM predefined 2 Â 2 array. The overall results of the analysis distinguished two dominant underwater soundscapes, associating them mainly to the seasonal changes in the nautical tourism and fishing activities within the study area and to the wind and wave action. The analysis identified recreational vessels as the dominant anthropogenic source of underwater noise, particularly during the tourist season. The method demonstrated to be an efficient tool in predicting the SAN levels based on the vessel distribution, indicating also the possibility of its wider implication for marine conservation.
The striped dolphin (Stenella coeruleoalba) is not a common cetacean species in the northern Adri... more The striped dolphin (Stenella coeruleoalba) is not a common cetacean species in the northern Adriatic Sea. Its presence is generally related to deeper offshore areas beyond the continental shelf. Despite this fact, the analysis of data collected over the past 5 years indicates unusual site fidelity of a single individual in the relatively shallow Vinodol Channel of the northern Croatian Adriatic Sea. Summarizing the available data on its recent occurrence, this paper contributes to the current limited knowledge on striped dolphin presence and associations not only in this region. Prugasti dupin (Stenella coeruleoalba) ne predstavlja uobi~ajenu vrstu za hrvatski dio sjevernog Jadrana. Obi~no nastanjuje duboka i otvorena mora iza kontinentalnog {elfa. Unato~tome, analiza podataka sakupljenih tijekom proteklih 5 godina ukazuje na neuobi~ajenu privr`enost jedinke prugastog dupina relativno plitkom podru~ju Vinodolskog kanala u hrvatskom dijelu sjevernog Jadrana. Sveukupni podaci o njegovom pojavljivanju predstavljeni su u ovom radu, pridonose}i time dosada{njm ograni~enim saznanjima o prisutnosti prugastih dupina, i to ne samo na ovom podru~ju.
The waters of the Cres-Lošinj archipelago are subject to intense boat traffic related to the high... more The waters of the Cres-Lošinj archipelago are subject to intense boat traffic related to the high number of leisure boats frequenting this area during the summer tourist season. Boat noise dominates the acoustic environment of the local bottlenose dolphin (Tursiops truncatus) population. This study investigates the spatial and temporal change in the underwater noise levels due to intense boating, and its effect on the distribution of the bottlenose dolphins. In the period 2007-2009 sea ambient noise (SAN) was sampled across ten acoustic stations. During data collection the presence of leisure boats was recorded if they were within 2 km of the sampling station. Bottlenose dolphin spatial distribution was monitored in the same period. Results showed a strong positive correlation between high SAN levels and boat presence, particularly in the tourist season. Dolphin distribution indicated significant seasonal displacements from noisy areas characterized by the intense leisure boating.
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Papers by Nikolina Rako