Carrying Capacity Of Lake Toba In North Sumatra Is Being Determined

The Indonesian Aquaculture Society (IAS) held a discussion in early July with stakeholders representing national and local fisheries to determine the carrying capacity of Lake Toba in Medan, North Sumatra. The meeting was expected to agree on a common issue, as there have been various carrying capacity numbers with different perceptions such as 10,000, 30,000, 35,000, 50,000 and 55,000 metric tons (MT) per year of fish production. Carrying capacity is the maximum number of organisms of a particular species that can be supported indefinitely in a given environment.
The lake is currently in mesotroph condition due to excessive pollutants, particularly phosphorous waste, which is being blamed on the aquaculture industry and some want the lake to be returned back to its original oligotroph condition. Academicians, however, stated that carrying capacity would be dynamic by time and that the phosphorous waste comes mainly from municipalities’ detergents around the lake. They also asserted that it is impossible to return the lake to its original pristine condition. They suggested that all of these factors be well managed based on scientific findings and regulations.
Aquafarm Nusantara of Regal Springs) and PT. STP Farm of JAPFA, representing the tilapia aquaculture industry and certified by Global GAP, BAP, BRC, Friends of the Sea, and ASC, claimed that, based on regular and strict environmental monitoring, the lake’s carrying capacity would be between 50,000 to 70,000 MT/year of fish production (current annual productions of those farms are 50,000 and 2,000 MT, respectively) and further stated that they would not destroy their “own home” by not implementing responsible production systems as required by both their consumers and nature. In addition, they maintained that they have been using high digestible fish feeds with very low phosphorous levels to reduce unnecessary wastes. It was agreed that carrying capacity level is being determined by those parties and is expected to be issued this year.
USSEC Southeast Asia Aquaculture Indonesia has been conducting feed-based aquaculture demonstration on tilapia aquaculture in floating net cage culture system in Lake Toba, North Sumatra using U.S. Soy in feed ingredients to sustain the aquaculture production system in the lake.

Tilapia culture in floating net cages in Lake Toba, North Sumatra, Indonesia