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October Update: Orcas, Hammerheads, Humpback Whales and upcoming Papers

Group of Orcas Spotted Northeast Off Benguerra Island
On the 25th of September, a pod of killer whales (Orcinus orca) were encountered. Four individuals were identified a few miles northeast from Benguerra Island. The orcas surfaced several times, but moved mostly at a depth of 10 to 20 meters, heading south.

Orcas belong to the sub-order of toothed whales (odontocetes) and can grow to up to 10 meters. They are the most widely distributed of all dolphins and whales and can be found in every ocean. Orcas are commonly called ‘killer whales’ because of ancient sailors’ observations of orcas hunting larger whale species.

Upcoming Papers & Publications
We are excited to share three new articles which BCSS has contributed to be published mid-2022. The articles cover various subjects: elasmobranch species (sharks and rays) in Mozambique, jellyfish carbon export patterns in West Africa and underwater volcano seabed animals. See an overview of the scopes below.

“Patterns in elasmobranch species from southern Mozambique using scuba diving surveys, in partnership with Underwater Africa (PhD student Mr. Calum Murie)”

“Jellyfish carbon export patterns and their effects on seabed benthic animals ecology in West Africa continental margin”

“Underwater volcano seabed animals isotope changes after an earthquake and a typhoon”

September Wildlife Highlights
The BCSS team has recorded incredible marine species, from a pod of orcas to hammerheads surfacing, but it seems that there are not as many humpback whales in the BANP compared to previous seasons, despite an early start. The seawater is relatively cold for this time of the year at 24 ºC, which results in fewer surface activity(e.g. tuna), less bait balls and many animals being scattered offshore to save energy.

We recorded sightings of humpback whales on 13 days in the last month, all moving south and mostly found in the wider area on the east of the Bazaruto Archipelago.

  • September 1: Multiple humpback whales (Megaptera novaeangliae), moving south, sighted offshore the Bazaruto Archipelago.
  • September 5: Two loggerhead turtles (Caretta caretta) were spotted offshore the Bazaruto Archipelago.
  • September 12: A bull shark (Carcharhinus leucas) was sighted swimming midwater at St Sebastian, south of Benguerra Island.
  • September 16: A scalloped hammerhead (Sphyrna lewini) was recorded surfacing offshore.
  • September 20: A group of three bull sharks (Carcharhinus leucas) was spotted offshore. 
  • September 27: A group of three bull sharks (Carcharhinus leucas) was spotted offshore.
  • September 28: A very large group of spinner dolphins (Stenella longirostris) was seen feeding offshore, northeast from Benguerra Island.
  • October 1: A black marlin (Istiompax indica) was spotted jumping out of the water just east off Bazaruto Island (which is rare), together with a scalloped hammerhead (Sphyrna lewini) surfacing. A dorado (or mahi-mahi) (Coryphaena hippurus) was also sighted northwest off Benguerra Island.
Interesting Wildlife Behaviour: Hammerheads Surfacing We observed interesting behaviour of scalloped hammerheads (Sphyrna lewini) last month, identifying 20 individuals on the ocean surface in the Bazaruto Archipelago. Typically, hammerheads stay at depths between 100 and 200 meters, so the team was surprised to see so many on the euphotic zone. They were patrolling the area with their dorsal fins above sea level, looking for prey. Though scientists still debate the purpose of the shape of the hammerheads head, it is a commonly accepted theory that it allows the shark to scan a wider area of the ocean through their sensory organs.

Marine Debris Monitoring Update 
The BCSS team visits several locations around Benguerra Island to collect marine debris continuously, including seagrass meadows, mangrove forests and beaches. The collection of debris translates to valuable data, and we can see a clear distinction in types of waste found per site. Over time, we notice a decline in plastic material entering the ecosystems. All collections were sorted in our Waste Facility on site. See below for an overview of this month’s marine debris collections.

Volunteers Contributing to Data Collection and Conservation Work 
We had two interns and one volunteer at the research station last month, contributing to technical tasks like scouting places to release mooring for sensors and swapping sensors in moorings to inputting data into the databases. They also helped with field mapping for megafauna, checking new reefs to study fish diversity via surveys and assisting in the ocean with filming work. Having the extra hands of volunteers and interns is very helpful for our Marine Debris Monitoring program (theme 4), as they assisted with beach clean ups, marine debris monitoring management and preparation of the indirect plastic in the carbon cycle. Read more about interning or volunteering at BCSS here.

Permaculture Update 
As Mozambique is transitioning into spring, the gardening team has harvested sweet potatoes, and the last leafy greens and tomatoes. The spring crops have been planted, including aubergine, peppers, chilis and hibiscus. The pineapple plants are starting to fruit, and in preparation for summer we will plant more hardy crops such as peanuts, cowpea and maize at the start of rainy season in October.

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