Sailing with no wind

Copyright M.Costa/HEPCA

In the calm afternoon of Saturday June 19th, 2010, the sea was like a mirror and the observers could see well into the horizon and spot the smallest movement at the surface with their naked eye. Shortly after sighting a group of three common bottlenose dolphins (Tursiops truncatus) feeding and a pregnant female slowly making her way through the water, a researcher spotted a fin in the distance as the boat was getting back on the route. The fin she observed was not a typical dolphin fin as it was not triangular and unlike dolphin fins, it did not surface and submerge, but there was always a part visible. This made it easy for the captain to track and follow. The team was hoping for a shark sighting, but as the boat approached the surface swimmer, the shape of the dorsal fin hinted at something else, equally exciting. Once in close proximity of the fish, the dorsal fin was arisen and we could identify it. Its long snout and sail-like dorsal fin left no doubts, it was  a sailfish (Istiophorus platypterus).

Individuals of this species have been clocked at speeds of up to 110 Km/h which is the highest speed reliably reported in a fish. The sail is normally kept folded down and to the side when swimming, but it may be raised when the sailfish feels threatened or excited, making the fish appear much larger than it actually is. This tactic has also been observed during feeding, when a group of sailfish use their sails to “herd” a school of fish or squid. This sighting was incredibly breathtaking!

Ali Fahmi (HEPCA intern)

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