Minke whale

A new collaborative study provides new insight into how two species of minke whales utilize the Caribbean and neighboring Atlantic waters throughout their life cycle. The findings add further conservation value and significance to the relatively new Yarari marine sanctuary of the Netherlands. By combining scientific, citizen science and public information, this study provides key information which will help guide conservation efforts moving forward.

Minke whales are the smallest of the “great whales” and can be found in waters world-wide. There are actually two different species of Minke whale, the common minke whale, or northern minke whale (Balaenoptera acutorostrata) and the Antarctic minke whale, or southern minke whale (Balaenoptera bonaerensis).

Yarari Sanctuary

Minke whales are known to migrate over long distances, with both species using the warm waters of the Caribbean to breed and calf during the winter months. Within the Caribbean, there are a number of marine protected areas, such as the Yarari Marine Mammal and Shark Sanctuary, which includes the territorial waters around Bonaire, Saba, and St. Eustatius. In addition to providing vital protection of the marine ecosystem, the Yarari Sanctuary is used to help focus research for greater insight into the life cycles and migration patterns of both resident and migratory species. Understanding how these species travel during the year and use Caribbean waters is critical in designing effective conservation plans in the future.

New Study

A recent study brought together a wide array of researchers and conservation groups including the Institute of Environmental Sciences from Leiden University and the Aruba Marine Mammal Foundation. This study reviewed literature, citizen science and scientific records to compile spatial and temporal data for both species of minke whales. The goal of the study was to learn more about how these species use the Wider Caribbean Area throughout their life cycles.

In total, 130 records were collected, most of which were from scientific studies (100) and the rest from citizen science (30). Minke whales are notoriously inquisitive, frequently approaching boats, which makes them the perfect species to be spotted by citizen scientists. Improvements in civilian camera equipment, and increased initiatives to record and share biodiversity observations on social networks and public databases have led to a recent surge in citizen science reports for all species.

Findings

Photo credit: Hans Verdaat

This study was able to integrate scattered species records to provide new insights that point to the importance of the Yarari Sanctuary which lies in the center of an Eastern Caribbean wintering area for the common minke whale and thus add conservation value and significance to this relatively new marine sanctuary of the Netherlands. These new insights are in large part thanks to two previous studies conducted by Wageningen University & Research together with the Saba Bank Managing Unit and were generously funded by the Ministry of Agriculture, Nature and Food Quality (LNV). These latter results were aligned with similar studies and were found to be consistent with large-scale seasonal migration routes of the Minke whales.

Interestingly, this study highlighted that although it was previously believed that only the northern minke whale used the Gulf of Mexico, there were confirmed stranding incidents involving both species. Furthermore, the fact that there were strandings of minke whales throughout the year suggested that some whales stay year-round within the Gulf.

Report your Sightings

Every sighting can provide useful data that can contribute to the understanding needed to protect these species. Help further conservation efforts by reporting your (minke) whale (or other species) sightings and photos on the website Observation.org or download the free app (iPhone (iObs) & Android (ObsMapp)). These tools are available in over 40 languages and can be used by biologists, citizens and tourists alike.

For more information you can find the full report on the Dutch Caribbean Biodiversity Database by clicking the button below.

https://www.dcbd.nl/document/spatial-temporal-distribution-minke-whales-...

Article published in BioNews 46

Abstract
Until recently, minke whale sightings in the northern Atlantic Ocean (NA) were thought to belong
exclusively to the common species Balaenoptera acutorostrata (CMW). Historical records confirm
the presence of the CMW in the north-eastern Caribbean Sea during the winter months. However,
the Antarctic minke whale (B. bonaerensis) (AMW) has been recently confirmed in the NA and
Gulf of Mexico. We review and summarize the available records of both species to shed light on
their spatial–temporal occurrence in the Wider Caribbean Region and adjacent NA (WCR-NA).
We revised the literature, searched the internet (social networks and video-hosting websites),
downloaded records available in biodiversity platforms, and added visual and acoustical records
from the authors’ files. Finally, we used oceanographic model databases to search for patterns in
spatial–temporal distribution. We collected 130 records, where 128 (98.4%) were classified as
CMW, and 2 (1.6%) as AMW. Most (100, 76.9 %) records were contributed by scientists or
scientific studies, while 30 (23.1%) stemmed from citizen-science. Records included visual
sightings (71.5%), acoustic detections (16.2%), strandings (11.5%), and direct takes (0.8%). Most
records belong to the northern Caribbean (50.0%), eastern Caribbean north of Martinique (30.8%),
the Gulf of Mexico (10.0%), and the NA (9.2%), and were collected during the winter (66.2%) and
(early) spring (28.5%) months, especially over the Caribbean upwelling season (December-March,
83.8%). Most of the CMW records correspond to three types of water masses, and also seemed to
associate with extreme climatic events such as El Niño/La Niña. Calves/juveniles were recorded
only on 6 occasions (4.6%). Low primary productivity during migration may limit feeding
opportunities for these whales. Increases in large-scale visual and acoustical surveys, and citizenbased
initiatives has resulted in better availability of minke whale records within the study area.
Our review confirms the WCR-NA as a wintering ground of North Atlantic CMW.

The Antillean Island chain is a known breeding and calving ground for North Atlantic humpback whales (Megaptera novaeangliae). However, while most research efforts for this species have focused on the largest aggregation of whales, located on Silver Bank, off the northern coast of the Dominican Republic, there are still significant knowledge gaps with respect to humpback whale movements along the Antillean Island chain. Even less is known about the spatio-temporal distribution of other marine mammal and fish species in the region. This report summarizes analysis results of acoustic data (10-8000 Hz effective analysis bandwidth recorded at a 25% duty cycle), recorded on the north east of Saba Bank from October 2011 to April 2012. The results show the consistent presence of humpback whales in the vicinity of Saba Bank during their winter breeding season, occasional presence of minke whales and the presence of sound producing fish assemblages. Humpback whale song occurred from the end of December to the end of the recording period in April. From February to April humpback whale song was recorded on more than 89 % of all recording days, though it occurred most frequently in March. All recording days in March showed song presence, with an average of 8.5 ± 2.8 (mean ± SE) hours of recorded song per day. In contrast, for minke whale (Balaenoptera acutorostrata) 48 pulse trains (n = 32) were detected less frequently between February to April 2012. A variety of unidentified fish sounds were present throughout the recordings. Although the occurrence of these sounds was not quantified, notable fish choruses (e.g. grouper spp. Epinephelinae) consisting of one to two distinct pulsed calls in the frequency range of 100 - 600 Hz were documented from October to December 2011 in particular. The results of this pilot project highlight the feasibility of using passive acoustic monitoring (PAM) to explore year-round marine mammal and fish presence and distribution in otherwise understudied and remote field sites.