Marine Mammal Surveys on the JCR

The team of scientists on board including Ryan, the Marine Assistant, and I have been keeping a pretty constant watch for any signs of movement in the vast Atlantic Ocean. We want to document the marine mammals that we pass during our transit South. In order to record this data, we modified a GPS application to suit our survey. We've had great success so far.

  

                                             Keeping a close watch for marine mammals

After we left the port of Harwich, we spotted 33 Harbour Porpoises in the English Channel which was a surprise to us given that is operates as a busy shipping channel. Mark Whiffin, a researcher on board, who will be studying penguins at Bird Island captured this fantastic photo of a juvenile porpoise peaking his head above the surface. Porpoises are in the same taxonomic order as dolphins: Odontocetes, but belong to different families. Compared to dolphins, porpoises are chunky yet compact, they have a short, triangular dorsal fin and have a stubbed face compared to pronounced dolphin beaks. These small mammals are often overlooked because they rarely perform the acrobatic characteristics displays of many oceanic dolphins. Porpoises are generally shy and a brief glimpse of the dorsal fin and a small portion of the back is all that is normally seen so this is indeed a very special photo.

Harbour porpoises- Photo credit: Mark Whiffin

Short-beaked common dolphins also spotted in the English Channel- Photo credit: Ryan Mathews

During our transit, we've had large inquisitive groups of Atlantic spotted dolphins that have come towards the ship to bow ride in the waves generated from the ship as it slices through the water. These species are highly acrobatic and we've captured some great shots of them leaping out of the water. Interestingly, as these species age, dark spots form on their white belly and white spots increase on the dorsal (top) side of the dolphins. There is also a variant form of these species that does not have spots so the ID can be tricky for lone individuals. Thankfully, some of the researchers on board are equipped with epic 600 m zoom lenses and our evenings are often filled with lively discussions about what species we think we photographed that day.

Atlantic spotted dolphins- Stenella frontalis- bow riding

  

Atlantic spotted dolphin travelling- Photo credit: Mark Whiffin

Across the first 14 days of the survey, just before reaching the Equator, we recorded 464 dolphin individuals along with 65 whales and 14 seals. The map below shows the ship's track line as we by-passed the Bay of Biscay (a known hotspot for whale activity), then passed within 13 nautical miles (nm) of the Canary Islands and 130 nm East of Cape Verde.

The track-line of the JCR vessel just before we reached the Equator

We have plotted dolphin sightings on this map according to group size. We saw some sizable groups west of the English Channel and off Western Africa. Our dolphin sightings have tailed off as we move further from the coast (at a constant bearing of 191°) and into the heart of the Atlantic Ocean. 

A map of dolphin sightings according to group size

The first whale individual we saw was a fin whale in the Bay of Biscay. This was my first whale sighting so I was delighted that my first encounter was up-close; within 100 m off the starboard (right) side of the boat. Fin whales are in the Balaenopteridae family, commonly known as Rorqual, which comprises the largest group of baleen whales. They are characterised by ventral pleats which run from the chin towards the navel in all members of this family. The purpose of the pleats is to expand during feeding to allow whales to open their jaws widely and 'lunge feed', taking in huge mouthfuls of water to sift through the plankton. 

A fin whale arching its tail stock- Photo credit: Ryan Mathews

  A map of whale sightings according to group size

We also had a recent incredible sei whale encounter at 07:30 one morning. The bridge called over the tannoy that whales were ahead of the bow and within minutes a huge sei whale breached not once but eight times. I could have cried with joy! This is extremely rare behaviour from these species and has hardly been documented in the wild.

 

Sei whales breaching- Photo credit: Mark Whiffin

Moving further south and in the same parallel latitude as Mauritania, four sperm whales were sighted within 800 m of the boat. This was spectacular. Sperm whales are toothed whales so they do not have baleen plates and use echolocation for locating their prey. Incredibly, they can dive for up to 2 hours to 3km depths! Sperm whales' blow is very characteristic, often diffuse and puffy directed forward and to the left. For the subsequent next few days, after our first sperm whale sightings, we continued to spot sperm whale blows in the distance and even saw one breach- the sound reverberated through the water as it hit the surface. Killer whales predate juvenile sperm whales and as you may have seen from documentaries, sperm whales adopt an anti-predatory defence by sleeping in a Marguerite formation whereby the adult whales are upright in the water column protecting the juveniles.

Sperm whales blowing- Photo credit: Claire Fraser

Given this is not a proper scientific survey with dedicated transects, as many marine mammal surveys would normally conduct, we are engaging colleagues and crew on board and are collecting data through citizen science. Opportunistic sightings outside of our regular survey hours are recorded from reports given to us by our peers in the bar at night. 

While our motivation here is more public interest than scientific rigour, our surveys may be of benefit to both scientists and members of the public with a curiosity in marine mammals. And for us on board, they provides hours of excitement and a sense of near-disbelief...