Blacktip Reef Sharks (Carcharhinus melanopterus)
Blacktip reef sharks are a very frequent sighting on our Phi Phi diving tour, often with many sharks in your field of vision. We get all different sizes from the almost 2m adult females to the tiny pups. We generally schedule Koh Bida Nok for our first dive on the trip so blacktip reef sharks are one of the first animals you’ll see. A great start to your days diving.
They’re not a guaranteed sighting by any means but it’s very unusual not to see at least a couple. There are three main areas that the sharks like to cruise around in. The drop off point for the dive is a shallow bay and the most likely area to see them but sometimes they’re in the shallow areas on the east or west side.
If you don’t see them on the first dive, don’t panic, there is still a chance at Turtle Rock or Koh Bida Nai. Occasionally we’ll also divert to Palong Wall, the visibility can be lower at this dive site but if the sharks are around there can be many.
They Don’t Stay Still
Blacktip reef sharks are a requiem shark so like some but not all from this group they have to keep moving. It’s called obligate ram ventilation. Swimming with their mouths open passes the oxygen they require over their gills. It sounds very exhausting but thought to be just as energy efficient as other sharks than can rest on the bottom and pump water over their gills with their mouth muscles (buccal pumping). Our leopard sharks are a great example of the latter.
It’s not known if they can actually rest or sleep. Studies have suggested that the spinal cord sorts out the swimming so the brain can rest a little while the shark keeps moving. So when we see them in the day, probably it’s some kind of rest period.
We don’t see any hunting behaviour from our sharks so it’s safe to assume they feed mainly at night. Sharks incredible sensory adaptations give them an edge in low light conditions. The tiniest movement or even heartbeat can reveal the location of its prey to a shark. Reef fish, squid, cuttlefish, octopus and lobster are all on the menu and all abundant at Phi Phi. Blacktips work together when hunting and populations are thought to recognise each other and even have a hierarchy system.
Phi Phi is definitely a breeding area, as mentioned before we see sharks of all sizes. Blacktip reef sharks are viviparous meaning pups are born live and not from an egg case. The pups are 40 – 50cm long at birth and perfect little predators as soon as they are born. Depending on water temperature, the females are pregnant for 10 to 16 months and birth 2 – 10 pups at a time.
They’re a widespread shark with populations reported from the east coast of Africa, through Asia and all the way to the Hawaiian Islands. They’re exploited for their fins as are all shark species and need protecting. Although we’ve seen no evidence of shark finning locally. We have unfortunately seen photos of dozens of dead sharks at the fish market in Phuket Town.
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