Humpback Whales (Megaptera novaeangliae) in the Cape Verde Islands: Migratory Patterns, Resightings, and Abundance

Wenzel, Frederick W.; Broms, Fredrick; López-Suárez, Pedro; Lopes, Kátia Gianlupi; Veiga, Nádia Cristina Ferreira; Yeoman, Kate; Rodrigues, Manuel Simão Delgado; Allen, Judith; Fernald, Thomas W.; Stevick, Peter T.; Jones, Lindsey; Jann, Beatrice; Bouveret, Laurent; Ryan, Conor; Berrow, Simon; Corkeron, Peter J.

doi:10.1578/am.46.1.2020.21

Cited by 22 publications

(21 citation statements)

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“…Comprising just 0.7% of the entire catch, fewer humpback whales were landed than any other baleen whale species (Table 1), indicating that populations were already heavily depleted by whaling when the industry commenced in Scotland. As of 1993, humpback whale abundance has been increasing at 3.1% per annum in the western North Atlantic (Stevick et al, 2003); however, a distinct breeding population in Cape Verde remains precariously small (less than 300 individuals) with no discernable post‐whaling recovery (Ryan et al, 2014b; Wenzel et al, 2020). Numbers of humpback whales in Scottish waters remain very low (Hammond et al, 2017); however, opportunistic sightings suggest an increase in occurrence in inshore waters since 2010 (O'Neil, Cunningham & Moore, 2019; Leaper et al, in review).…”

Section: Discussionmentioning

confidence: 99%

Historical occurrence of whales in Scottish Waters inferred from whaling records

Ryan¹,

Calderan

Allison³

et al. 2022

Aquatic Conservation

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1. Archived logbooks detailing landings at Scottish shore-based whaling stations between 1903 and 1951 were used to map whale catch locations. Historical distribution and occurrence are inferred and summary statistics on total landings are updated for blue (Balaenoptera musculus), fin (Balaenoptera physalus), humpback (Megaptera novaeangliae), North Atlantic right (Eubalaena glacialis), sei (Balaenoptera borealis) and sperm (Physeter macrocephalus) whales: a total of 9,996 whales were caught during this period, which is 3.7% higher than previously reported and 25% higher for blue whales.2. The most frequently caught species were fin and sei whales. Whaling off Scotland in the 1920s contributed to the likely extinction of right whales in the eastern North Atlantic. Blue whales, once regularly hunted to the west of Scotland, are now rarely documented there and North-east Atlantic whaling appears to have had a significant and lasting impact on sei whales.3. Analysis of whaling effort indicates that catch rates remained high despite the depletion of some species. This, may be a consequence of two features of Scottish shore-based whaling: (1) the mixed species catch composition; and(2) the catching of whales as they migrated through Scottish waters.4. The findings of this study highlight the historical significance of the shelf-seas around Scotland as a habitat for some species, which was not apparent from previous studies. These results can inform where there may be potential for the recovery of some species in the future. 5. Current major threats in the North Atlantic include entanglement, ship strike and displacement owing to the effects of climate change. The baseline and historical information on distribution and seasonal occurrence examined here is important for informing spatial and temporal measures to reduce these threats. If populations are to recover post-whaling there is an increasing need to reduce threats such as ship strikes and entanglement, whose magnitude is proportional to whale density.

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Section: Discussionmentioning

confidence: 99%

Historical occurrence of whales in Scottish Waters inferred from whaling records

Ryan¹,

Calderan

Allison³

et al. 2022

Aquatic Conservation

Self Cite

251

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“…However, some individuals have been matched between Cape Verde and the southeastern Caribbean, as well as between the southeastern and northwestern Caribbean, demonstrating that the population units and boundaries are not as clear as previously thought (Stevick et al, 2016;MacKay et al, 2019). While the western North Atlantic humpback whale population has been increasing in recent years after the cessation of whaling, the Cape Verde population is still of considerable concern (Wenzel et al, 2020).…”

Section: Introductionmentioning

confidence: 92%

Seasonal and diel patterns in singing activity of humpback whales migrating through Bermuda

et al. 2022

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Humpback whales (Megaptera novaeangliae) produce song and non-song vocalisations, which allows their presence to be detected through passive acoustic monitoring. To determine the seasonal and diel acoustic presence and acoustic behaviour of humpback whales at the migratory stopover site off Bermuda, three hydrophones were deployed between March 2018 and April 2019 on Challenger Bank and the Bermuda platform. Song was the predominant vocalisation type encountered, with 65% of song recordings containing whale chorus and a clear seasonal trend of humpback whale occurrence in the spring and winter months from late December to mid-May. A strong diel pattern in singing activity was detected. Singing activity significantly increased at night relative to the daytime (p<0.01), whilst twilight periods were characterised by intermediate levels of singing. The song structure encountered in spring 2018 consisted of 18 units, 6 themes and 5 transitional phrases. The high occurrence of whale chorus and the strong seasonal and diel patterns of male humpback whale singing activity highlights the importance of Bermuda not just on their northward migration during spring, as described historically, but also on their southward migration during winter. Bermuda therefore constitutes a two-way migratory stopover site for humpback whales. The present study also provides Bermuda’s planning authorities with better constraints on the duration and intensity of anthropogenic activities in these waters.

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“…Recognised humpback whale breeding areas in the North Atlantic are Silver Bank in the Dominican Republic, the southeastern Caribbean around Guadeloupe and a small remnant of a once larger population around Cape Verde (Stevick et al, 2018;Wenzel et al, 2020). While the western North Atlantic humpback whale population has been increasing post-whaling, the Cape Verde population is still of concern (Wenzel et al, 2020). Using photoidentification, three individual humpback whales from Cape Verde were recently identified in Irish waters, but no matches were found with the Caribbean (Berrow et al, 2021).…”

Section: Figurementioning

confidence: 99%

Monitoring cetacean occurrence and variability in ambient sound in Scottish offshore waters

Geel¹,

Risch²,

Benjamins³

et al. 2022

Front. Remote Sens.

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The characterisation of marine soundscapes allows observation of spatiotemporal distribution of vocalising species and human activities, which can inform an assessment of their interactions. Such data are important for monitoring the ecological status of marine habitats. The Scottish Atlantic Frontier is an important habitat for a variety of cetacean species. Historic whaling has heavily impacted several species inhabiting these waters and current comprehensive information about seasonal occurrence and distribution is lacking for all species. This study presents year-round passive acoustic monitoring data from ten sites in this understudied region. The three most offshore sites were examined for baleen whale vocalisations, and four species were regularly detected. Fin whale detections peaked from October to January and were at their lowest during May and June. Humpback whale song was detected as early as January but showed a strong seasonal peak in March and April. In contrast, minke whales were detected regularly throughout the year but with a peak in detections from October to November, when sei whales were also detected. All monitoring sites showed frequent occurrence of odontocete echolocation clicks and whistles. Comprised mainly of delphinid vocalisations, whistles and clicks were detected on an almost-daily basis among the offshore sites, with a slight reduction in detections from May to July particularly among the more inshore sites. Ambient sound levels (root-mean-square sounds pressure level; SPL) varied by site and season in relation to species presence, anthropogenic contributions, and environmental conditions. Monthly median SPL across the array varied up to 18 dB within 1/3-octave bands. Throughout the year, variability in median SPL was lowest in the higher frequency bands (>10 kHz), while highest variability was found between January to July in specific lower frequency bands (<1 kHz). Results from this study demonstrate the value of passive acoustic data in providing novel baseline information about cetacean occurrence and distribution in Scottish offshore habitats where data are limited and outdated. The results will feed into statutory reporting on underwater noise, support the identification and designation of future marine protected areas for cetaceans, and help guide management of future human-marine mammal interactions in Scottish offshore waters.

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Humpback Whales (Megaptera novaeangliae) in the Cape Verde Islands: Migratory Patterns, Resightings, and Abundance

Cited by 22 publications

References 0 publications

Historical occurrence of whales in Scottish Waters inferred from whaling records

Historical occurrence of whales in Scottish Waters inferred from whaling records

Seasonal and diel patterns in singing activity of humpback whales migrating through Bermuda

Monitoring cetacean occurrence and variability in ambient sound in Scottish offshore waters

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