Cerchio, S.,Willson, A.,Muirhead, C.,Al Harthi, S.,Baldwin, R.,Bonato, M,Collins, T.,Di Clemente, J.,Dulau, Violaine,Estrade, Vanessa,Latha, G,Minton, A. Gianna.,Sarrouf Willson, M.
Geographic variation in song indicates both isolation of Arabian Sea humpback whales and presence of Southern Hemisphere whales off Oman Technical Report
no. 342, 2018, ISSN: IWC/SC67B/CMP19.
Abstract | Links | BibTeX | Tags: Humpback Whale, India, Indian Ocean, megaptera novaeangliae, Oman, population structure, Reunion, song
@techreport{,
title = {Geographic variation in song indicates both isolation of Arabian Sea humpback whales and presence of Southern Hemisphere whales off Oman},
author = {Cerchio, S.,Willson, A.,Muirhead, C.,Al Harthi, S.,Baldwin, R.,Bonato, M,Collins, T.,Di Clemente, J.,Dulau, Violaine,Estrade, Vanessa,Latha, G,Minton, A. Gianna.,Sarrouf Willson, M.},
url = {https://arabianseawhalenetwork.org/wp-content/uploads/2018/05/sc_67b_cmp_19_oman-humpback-whale-song-analysis-and-comparison-1.pdf},
issn = {IWC/SC67B/CMP19},
year = {2018},
date = {2018-01-01},
journal = {Document presented to the Scientific Committee of the International Whaling Commission},
number = {342},
pages = {31},
publisher = {International Whaling Commission},
abstract = {Existing genetic, demographic and behavioral evidence indicates that Arabian Sea humpback whales
represent an isolated and unique population. The population exhibits a Northern Hemisphere breeding
cycle, is believed to feed year-round, and lacks the typical latitudinal migrations and seasonal separation
of breeding and feeding ecology exhibited by other populations of humpback whales globally. A key
feature of humpback whale breeding behavior is the male acoustic breeding display, song, studied
extensively around the world. Key characteristics of humpback whale song include: all males within a
population share the same song patterns (phrases); a population’s song changes progressively over time;
and populations that do not overlap or exchange individuals have distinctly different songs, whereas
populations in contact share some or all phrases. Here we use long-term acoustic monitoring off the coast
of Oman to further assess the isolation of the Arabian Sea population. A total of 76 samples (amounting
to 4,434 minutes of recording) of Arabian Sea song collected between 2011 and 2013 were examined, and
phrase content was characterized and compared to 23 samples (totaling 202 min of recording) collected
during the same years in the Southwest Indian Ocean from Reunion Island and the Comoros Islands. Song
from the Arabian Sea and the Southwest Indian Ocean was distinct across the entire study period, with no
evidence for shared phrases in any year. In addition, song fragments recorded off western India in 2011
were composed of two phrases present in the Oman song, suggesting continuity across the Arabian Sea.
Moreover, the Arabian Sea song exhibited a markedly atypical low level of temporal variation, with song
phrases remaining virtually unchanged during the three examined breeding seasons. Notably, Southwest
Indian Ocean song was recorded off the coast of Oman in August 2012 (Boreal summer, Austral winter).
This song was recorded on multiple days and included multiple simultaneous singers over a 25 day period
indicating the presence of more than a single accidental vagrant Southern Hemisphere animal. We suggest
that these Southern songs were produced by Southwest Indian Ocean animals moving into the Arabian
Sea, and that this may be more common than is currently thought. The low level of temporal variation
shown by the Arabian Sea males along with the lack of adoption of the Southwest Indian Ocean song
material, further indicate the uniqueness and distinct nature of this population. It seems possible that
isolation mechanisms exist that may inhibit the mixing of the Arabian Sea population with Southern
Hemisphere animals, and that this may be reflected in the observed atypical song behavior.},
keywords = {Humpback Whale, India, Indian Ocean, megaptera novaeangliae, Oman, population structure, Reunion, song},
pubstate = {published},
tppubtype = {techreport}
}
Existing genetic, demographic and behavioral evidence indicates that Arabian Sea humpback whales
represent an isolated and unique population. The population exhibits a Northern Hemisphere breeding
cycle, is believed to feed year-round, and lacks the typical latitudinal migrations and seasonal separation
of breeding and feeding ecology exhibited by other populations of humpback whales globally. A key
feature of humpback whale breeding behavior is the male acoustic breeding display, song, studied
extensively around the world. Key characteristics of humpback whale song include: all males within a
population share the same song patterns (phrases); a population’s song changes progressively over time;
and populations that do not overlap or exchange individuals have distinctly different songs, whereas
populations in contact share some or all phrases. Here we use long-term acoustic monitoring off the coast
of Oman to further assess the isolation of the Arabian Sea population. A total of 76 samples (amounting
to 4,434 minutes of recording) of Arabian Sea song collected between 2011 and 2013 were examined, and
phrase content was characterized and compared to 23 samples (totaling 202 min of recording) collected
during the same years in the Southwest Indian Ocean from Reunion Island and the Comoros Islands. Song
from the Arabian Sea and the Southwest Indian Ocean was distinct across the entire study period, with no
evidence for shared phrases in any year. In addition, song fragments recorded off western India in 2011
were composed of two phrases present in the Oman song, suggesting continuity across the Arabian Sea.
Moreover, the Arabian Sea song exhibited a markedly atypical low level of temporal variation, with song
phrases remaining virtually unchanged during the three examined breeding seasons. Notably, Southwest
Indian Ocean song was recorded off the coast of Oman in August 2012 (Boreal summer, Austral winter).
This song was recorded on multiple days and included multiple simultaneous singers over a 25 day period
indicating the presence of more than a single accidental vagrant Southern Hemisphere animal. We suggest
that these Southern songs were produced by Southwest Indian Ocean animals moving into the Arabian
Sea, and that this may be more common than is currently thought. The low level of temporal variation
shown by the Arabian Sea males along with the lack of adoption of the Southwest Indian Ocean song
material, further indicate the uniqueness and distinct nature of this population. It seems possible that
isolation mechanisms exist that may inhibit the mixing of the Arabian Sea population with Southern
Hemisphere animals, and that this may be reflected in the observed atypical song behavior.
represent an isolated and unique population. The population exhibits a Northern Hemisphere breeding
cycle, is believed to feed year-round, and lacks the typical latitudinal migrations and seasonal separation
of breeding and feeding ecology exhibited by other populations of humpback whales globally. A key
feature of humpback whale breeding behavior is the male acoustic breeding display, song, studied
extensively around the world. Key characteristics of humpback whale song include: all males within a
population share the same song patterns (phrases); a population’s song changes progressively over time;
and populations that do not overlap or exchange individuals have distinctly different songs, whereas
populations in contact share some or all phrases. Here we use long-term acoustic monitoring off the coast
of Oman to further assess the isolation of the Arabian Sea population. A total of 76 samples (amounting
to 4,434 minutes of recording) of Arabian Sea song collected between 2011 and 2013 were examined, and
phrase content was characterized and compared to 23 samples (totaling 202 min of recording) collected
during the same years in the Southwest Indian Ocean from Reunion Island and the Comoros Islands. Song
from the Arabian Sea and the Southwest Indian Ocean was distinct across the entire study period, with no
evidence for shared phrases in any year. In addition, song fragments recorded off western India in 2011
were composed of two phrases present in the Oman song, suggesting continuity across the Arabian Sea.
Moreover, the Arabian Sea song exhibited a markedly atypical low level of temporal variation, with song
phrases remaining virtually unchanged during the three examined breeding seasons. Notably, Southwest
Indian Ocean song was recorded off the coast of Oman in August 2012 (Boreal summer, Austral winter).
This song was recorded on multiple days and included multiple simultaneous singers over a 25 day period
indicating the presence of more than a single accidental vagrant Southern Hemisphere animal. We suggest
that these Southern songs were produced by Southwest Indian Ocean animals moving into the Arabian
Sea, and that this may be more common than is currently thought. The low level of temporal variation
shown by the Arabian Sea males along with the lack of adoption of the Southwest Indian Ocean song
material, further indicate the uniqueness and distinct nature of this population. It seems possible that
isolation mechanisms exist that may inhibit the mixing of the Arabian Sea population with Southern
Hemisphere animals, and that this may be reflected in the observed atypical song behavior.
Rabearisoa, Njaratiana,Sabarros, Philippe S.,Romanov, Evgeny V.,Lucas, Vincent,Bach, Pascal
Toothed whale and shark depredation indicators: A case study from the Reunion Island and Seychelles pelagic longline fisheries Journal Article
In: PLOS ONE, vol. 13, no. 440, pp. e0202037, 2018.
Abstract | Links | BibTeX | Tags: Bycatch, depredation, Indian Ocean, longline, Reunion, Seychelles
@article{,
title = {Toothed whale and shark depredation indicators: A case study from the Reunion Island and Seychelles pelagic longline fisheries},
author = {Rabearisoa, Njaratiana,Sabarros, Philippe S.,Romanov, Evgeny V.,Lucas, Vincent,Bach, Pascal},
url = {https://doi.org/10.1371/journal.pone.0202037},
year = {2018},
date = {2018-01-01},
journal = {PLOS ONE},
volume = {13},
number = {440},
pages = {e0202037},
publisher = {Public Library of Science},
abstract = {Depredation in marine ecosystems is defined as the damage or removal of fish or bait from fishing gear by predators. Depredation raises concerns about the conservation of species involved, fisheries yield and profitability, and reference points based on stock assessment of depredated species. Therefore, the development of accurate indicators to assess the impact of depredation is needed. Both the Reunion Island and the Seychelles archipelago pelagic longline fisheries targeting swordfish (Xiphias gladius) and tuna (Thunnus spp.) are affected by depredation from toothed whales and pelagic sharks. In this study, we used fishery data collected between 2004 and 2015 to propose depredation indicators and to assess depredation levels in both fisheries. For both fisheries, the interaction rate (depredation occurrence) was significantly higher for shark compared to toothed whale depredation. However, when depredation occurred, toothed whale depredation impact was significantly higher than shark depredation impact, with higher depredation per unit effort (number of fish depredated per 1000 hooks) and damage rate (proportion of fish depredated per depredated set). The gross depredation rate in the Seychelles was 18.3%. A slight increase of the gross depredation rate was observed for the Reunion Island longline fleet from 2011 (4.1% in 2007–2010 and 4.4% in 2011–2015). Economic losses due to depredation were estimated by using these indicators and published official statistics. A loss of 0.09 EUR/hook due to depredation was estimated for the Reunion Island longline fleet, and 0.86 EUR/hook for the Seychelles. These results suggest a southward decreasing toothed whale and shark depredation gradient in the southwest Indian Ocean. Seychelles depredation levels are among the highest observed in the world revealing this area as a “hotspot” of interaction between pelagic longline fisheries and toothed whales. This study also highlights the need for a set of depredation indicators to allow for a global comparison of depredation rates among various fishing grounds worldwide.},
keywords = {Bycatch, depredation, Indian Ocean, longline, Reunion, Seychelles},
pubstate = {published},
tppubtype = {article}
}
Depredation in marine ecosystems is defined as the damage or removal of fish or bait from fishing gear by predators. Depredation raises concerns about the conservation of species involved, fisheries yield and profitability, and reference points based on stock assessment of depredated species. Therefore, the development of accurate indicators to assess the impact of depredation is needed. Both the Reunion Island and the Seychelles archipelago pelagic longline fisheries targeting swordfish (Xiphias gladius) and tuna (Thunnus spp.) are affected by depredation from toothed whales and pelagic sharks. In this study, we used fishery data collected between 2004 and 2015 to propose depredation indicators and to assess depredation levels in both fisheries. For both fisheries, the interaction rate (depredation occurrence) was significantly higher for shark compared to toothed whale depredation. However, when depredation occurred, toothed whale depredation impact was significantly higher than shark depredation impact, with higher depredation per unit effort (number of fish depredated per 1000 hooks) and damage rate (proportion of fish depredated per depredated set). The gross depredation rate in the Seychelles was 18.3%. A slight increase of the gross depredation rate was observed for the Reunion Island longline fleet from 2011 (4.1% in 2007–2010 and 4.4% in 2011–2015). Economic losses due to depredation were estimated by using these indicators and published official statistics. A loss of 0.09 EUR/hook due to depredation was estimated for the Reunion Island longline fleet, and 0.86 EUR/hook for the Seychelles. These results suggest a southward decreasing toothed whale and shark depredation gradient in the southwest Indian Ocean. Seychelles depredation levels are among the highest observed in the world revealing this area as a “hotspot” of interaction between pelagic longline fisheries and toothed whales. This study also highlights the need for a set of depredation indicators to allow for a global comparison of depredation rates among various fishing grounds worldwide.