Eco Koh Tao and Crystal Dive have teamed up to go on a mission…and you might say its rather slow!
We currently have an outbreak of Drupella Snails in the coral reefs here in Koh Tao and while they are interesting to look at they are responsible for extensive coral reef damage, once an outbreak occurs removal must take place for the balance to be restored.
Drupella snails feed off of living coral tissue, particular favourites being the stag horn and plate coral colonies here on Koh Tao.
The snails leave white tissue scars on affected coral and can usually be found congregated at the base or deep down in-between the coral branches.
Adults have a robust looking shell, 2-3cm long, are covered in small spikes and are deep purple in colour. Juveniles are usually 0.5-1cm long and are white in colour.
These outbreaks, or overpopulations, have led to dramatic loss in living coral tissue, reduced reef resilience and recovery, population regime shifts, and possibly increased disease occurrence.
Eco Diving, Koh Tao
The outbreaks occur due to more of the larvae and juveniles surviving, just like the case of Crown of Thorns Starfish, one female can produce over 100,000 eggs, which will turn to free-swimming larvae.
But, when the fish are removed due to over fishing, or the water quality decreases due to nutrient inputs, then more larvae survive to adulthood. Once the become adults they have very few natural predators, as they are a very unattractive food source.
There are a lot of projects researching this in Thailand especially, although they have also been found causing lots of damage in places such as Kenya, Australia, Hong Kong, and the Red Sea.