Lake Toba in Sumatra, Indonesia is the world’s largest volcanic lake. The water occupies the enormous caldera of a super volcano which erupted approximately 75,000 years ago. It was one of the most violent geological events in history. Today the lake is home to millions of fish with many being reared by local fish farmers. This month literally millions of the fish were discovered dead in the farmer’s cages. Aquafarmers lost all of their stock in just a couple of days.
Were Carp Pellets to Blame?
The fish concerned were principally Carp and Nile Tilapia. As a result of this mystery the farmers have sustained huge losses and many say they have been ruined by the unexpected event. What has yet to be established is the cause of death. Some local people have blamed the fish farmers themselves saying that they polluted the water with large volumes of uneaten carp pellets. However, carp pellets are not thought to be the only cause of the destruction. Low dissolved oxygen levels have been recorded in the lake and this is believed to be the result of both man-made and natural causes.
No Single Cause?
The region surrounding lake Toba has been suffering from a lengthy drought and overcast conditions and it is thought that this has played a significant role in the recent low oxygen levels of the lake water. The lack of sun has reduced oxygen production in deep water and the affected water may have then risen closer to the surface. The volume of uneaten carp pellets and excessive fish waste may also be at fault. The waste would have had a greater impact that usual because of the low water level. Recriminations have been thrown around and these have also included accusations that the farmers have been rearing too many fish in their cages.
Extensive tests are now being carried out by Indonesian government researchers to establish exactly what happened to the fish. There is a chance that volcanic activity has played a role because this type of extreme event with so many fish dying has never happened before.
Hundreds of local volunteers are now helping to clear the lake of carcasses and to dispose of them. Using heavy lifting equipment and plastic bags, the fish are being hauled onto dry land and a giant hole has been dug for their burial.
The End of Days
Some harbingers of doom are suggesting that the event could be a sign that the apocalypse is approaching. The Bible warned that the end of days would be preceded by large scale deaths of animals and sea life. We think that the low oxygen levels are a more likely explanation but as to the cause of it, well it’s still an unknown!
The episode does appear to be a salutary lesson in the importance of good feeding practices and maintaining the right water quality. Too many fish, too much uneaten food and too little sunshine appear to have combined to create the perfect storm in this case. If you visit your local fishing lake then try not to pollute it with carp pellets and other waste and debris. It may not be the caldera of a super volcano but the water still needs to be looked after.