Bengaluru: Refreshed lakes, dying fish

Bengaluru urban lakes have been seeing a spate of fish-kills in recent times, and these have raised many eyebrows, sparking discussions regarding the quality of water in our lakes. Obviously, fish-kills are an indicator of both the water quality and lake health. However, the cause of the kills can be many, and an immediate post-mortem is essential.

During a major fish-kill of Ulsoor lake in 2016, the cause identified was depleting dissolved oxygen levels in the water, especially during the night hours between 11 pm and 5 am when the level had dropped to zero.

The primary cause identified was algae, which was in abundance due to the very high share of nutrients, especially phosphate and nitrate available in the lake. The lake was, technically, hyper eutrophicated with phosphates being 9 PPM (Part Per Million) instead of below 1 PPM.

Raw sewage

The influx of raw sewage or treated water where the nutrients are not removed to the Central Pollution Control Board (CPCB) standards was seen as the primary cause. It was also seen that the fishermen were misguided to add extra nutrient for better fish growth, which also added to the kills.

Read | ‘Stop sewage inflow, watch fish thrive’

Fish-kills are indicators of mismanagement of urban lake maintenance after rejuvenation that cost crores of rupees. Fishing rights contracts are given out by the Fisheries Department which do not do any coordination with the owner, the regulator or custodian of the lake.

The department, despite having a water lab at Hebbal lake (Fisheries Research and Information Centre) does not publish or do any regular water quality monitoring of the lakes. Even minimal guidance to the fisherman regarding the species and ecological balancing is rarely seen.

Exploitative fishing

Exploitative commercial fishing with only two or three varieties of commercially valued fish, with total disregard to ecological balancing and lake water biodiversity, are also primary causes for the fish kills.

Ornithologists have been warning about the loss of bird biodiversity due to rampant, exploitative commercial fishing with only two to three species. The smaller species are totally missing in some of the city lakes, especially the silver and grass carps.

Lakes that are denoted as E category by the Karnataka State Pollution Control Board (KSPCB) are being contracted for fishing rights. So, obviously there will be fish-kills in these lakes and we should not be astonished.

Rejuvenation issues

The other factors that contribute to fish-kills is lake rejuvenation itself. Although there are High Court orders regarding proper rejuvenation process, it is not being followed. The lakes are rejuvenated in the Soup Bowl design instead of the natural tapering design with inlets being shallow and the main bund being deep.

The natural tapering lake-bed design allows fish and plant biodiversity to flourish and increases the aquatic birds biodiversity too, thus ushering in ecological balancing. Lake rejuvenation have to be purpose-oriented. The purpose / functionality of the lake could be flood mitigation, rainwater harvesting, irrigation, recreation or sports, but the underlining foundation should be environmental and ecological balancing.

Coordination, a must

The government departments that are duty-bound for maintenance of the water quality of lakes should consult and coordinate with one another. KSPCB cannot be a pollution identification board but pinpoint the source of pollution and take punitive actions, which is rarely done.

The Fisheries Department should also take responsibility beyond just awarding rights contracts for maintenance of lake water quality, and regularly guide fisherman on multiple factors, including maintenance of biodiversity and its importance in sustainable fishing.

The regulatory Karnataka Tank Conservation and Development Authority (KTCDA) should at least convene coordination meetings between the lake custodian, KSPCB and Fisheries Department before awarding fishing rights.

Regulator’s duty

KTCDA is also duty bound to approve the rejuvenation detailed project reports. Hence, the onus of scientific, ecological and environmental rejuvenation in accordance to the engineering standards and court orders totally lies on KTCDA.

The Custodians (Urban Local Bodies / Panchayaths /Forest Department, etc.,) have more responsibilities as they are in-charge of day-to-day activities and maintenance. Hence, it is even more important for coordinating with other governmental agencies, including the fishermen community.

Last, but not the least, the citizens are also responsible for the fish-kills by throwing garbage into the feeder channels (drains) or letting raw sewage or partially treated water into the drains that eventually end up in lakes.

(The writer is Co-Founder, Friends of Lakes)