Dykning med Requiem-hajer

Koh Lantas Marineliv | Carcharhinidae

Requiem-hajer er vandrende, levende hajer i varme have (nogle gange i brakvand eller ferskvand) og omfatter sortspids-revhajen, som man finder, når man dykker omkring Koh Lanta ved både Bida-øerne og Koh Haa.

Der er 54 arter i familien Carcharhinidae, klassificeret i 12 slægter. Farvandet omkring Koh Lanta er hjemsted for flere af disse kritisk truede arter.

Ud over den almindeligt forekommende sortspidsrevhaj er der andre arter af requiemhajer, som man ved lever i området, men som man sjældent ser, nemlig sygeplejerskehajen, grå revhaj, tyrehaj og grå bambushaj.

Requiem-hajer har torpedolignende kroppe, som gør dem til hurtige og adrætte jægere. De har en række byttedyr, herunder benfisk, blæksprutter, hummer, skildpadder, havpattedyr, havfugle og andre hajer og rokker.

De betragtes ofte som havets »skraldespande« og spiser næsten hvad som helst, inklusive plastikaffald. Requiem-hajer er typisk 1-3 m lange, men nogle arter kan blive op til 7 m lange.

Vi ser for det meste revhajer, når vi dykker ved Bida-øerne og nogle gange ved Koh Haa og Koh Phi Phi.

1 arter fundet på denne side:

Blacktip Reef Shark (Carcharhinus melanopterus)

Blacktip Reef Shark

(Carcharhinus melanopterus)

The Blacktip Reef Shark (Carcharhinus melanopterus) is easily identified by the prominent black tips on its fins (especially on the first dorsal fin and its tail fin). The black tips are highlighted by lighter-colored borders, which are especially noticeable on the first dorsal fin and lower tail fin.

The Blacktip Reef Shark has a short, wide, rounded snout and slightly large, oval eyes and saw-like teeth. Its white belly and dark back allow it to camouflage with the darker seafloor and the brighter ocean surface.

Carcharhinus melanopterus @ Koh Bida

The Blacktip Reef Shark prefers swimming in shallow waters just a few meters deep, and most Blacktip Reef Sharks are found over reef ledges and sandy flats. Blacktip Reef Sharks have extremely small home ranges and exhibit strong site attachment, remaining within the same local area for up to several years at a time.

Blacktip Reef Shark @ Koh Bida

Blacktip Reef Sharks @ Koh Haa

Blacktip Reef Sharks are active predators of small bony fishes, including Mullet, Groupers, Jacks, Wrasses, Surgeonfish, etc. Their diet also includes Cephalopods such as squid, octopus and cuttlefish, and crustaceans such as Mantis Shrimp. Blacktip Reef Sharks have sometimes been observed hunting cooperatively by 'herding' small schools of fish.

Females give birth to two to five young, and newborn sharks are usually found in shallower water than adults, possibly roaming in large groups, to avoid being eaten by groupers and other sharks.

Blacktip Reef Sharks reach maturity at an average age of about 4 years old for males and 7 years old for females and can live to 13 years of age, sometimes longer. These sharks may typically reach 1.5 - 1.6 m, though on rare occasions, individuals may reach up to 1.8 m. Blacktip Reef Sharks show high capacity for wound healing and recovery following injury.

Timid and skittish, the Blacktip Reef Shark is difficult to approach and seldom poses a danger to humans unless roused by food. People wading through shallow water are however at risk of having their legs bitten by mistake, though this does not usually result in serious injury.

Interestingly, the Blacktip Reef Shark can fully jump out of the water, one of the few sharks that can display this behaviour.