JOIN USRecurring fishkills in lakes across Bengaluru have literally raised a stink. But the dramatic scenes of lakhs of dead, floating fish have brought to the fore the extreme pollution of these water bodies. At stake is not just the environment but a food chain dependent on a growing market for freshwater fish sourced from within the city. This delicate ecosystem is now under serious threat.
Reports that these dead fish, obviously contaminated and decayed, found their way to the markets for sales are shocking enough. But this also raises questions about the quality standards internalised by the network of fish breeders, suppliers and retailers. Is it safe to consume the fish grown in lakes fed by untreated domestic sewage and industrial effluents?
The fishkill in Hebbal lake recently and similar episodes in the Ulsoor and Devarabisanahalli lakes earlier have been attributed to asphyxiation due to sudden and considerable fall in the Dissolved Oxygen (DO) levels. Scientists have also blamed ammonia toxicity. To make it worse, most lakes have no Sewage Treatment Plants (STPs), and the few ones that exist are not fully functional.
Exotic fish factor
Analysing the fishkill in Ulsoor lake, an Indian Institute of Science (IISc) study had drawn attention to another cause: Indiscriminate introduction of exotic fish species such as African Catfish and Tilapia, threatening the survival of the fish native to a particular lake. The exotic species, the study had found, eliminates the native biota and affects the local biodiversity.
High density of fish beyond sustainable levels is another critical factor, say fisheries experts. Greedy fish farmers try to grow more in a limited space, drastically depleting the available DO. The sensitive ones die first, before the massive fishkill strikes. “The farmers have been reportedly asked not to do this, but they don’t listen,” complains a fisheries department official.
To understand why a conducive ecosystem is essential for fish culture, a closer look at the entire breeding process is critical. As the department official explains, fish could be grown either in lakes and tanks or in irrigation tanks that are 4-5 ft deep. “Upto 15-20 tons per hectare can be grown in this form of culture. Some species could go upto 40 tonnes.”
In natural water bodies such as lakes, the fisheries department either leases out the rights or issues licences at a nominal prices. The licence is valid for a year, renewable every year upto a maximum of five. Fast growing fish seeds are sourced from different parts of the State or even Andhra Pradesh. Once harvested, most fish are sold in markets and fish outlets across Bengaluru.
By one estimate, the Rohu variety constitutes almost 60% of the freshwater fish retailed in the city. About 20% are Catla, while Mrigal Carp, Common Carp, Grass Carp and other smaller species make up the rest.
Discrete buyers
Fish harvested in the city lakes do find their way to hotels, retail outlets and some big markets. But many buyers are now discrete enough to spot the difference. “I look at the excretion point of the fish and can see the colour change. Fresh fish are reddish,” notes Rohijit Sinha, an IT executive from Murugeshpalya. He frequents the HAL fishmarket for his weekly purchase.
Fish retailer, SA Rasheed notes that freshwater species sourced from the city lakes do not retain their freshness beyond a day. “The decay starts from the intestine and quickly spreads to the entire body. We don’t stock them. Our fish comes from Nellore in Andhra Pradesh and Tamilnadu,” he explains.
Freshwater fish is much sought after by Bengalureans of Bengali, Odisha and Assamese origins. But most Keralites and Kannadigas from coastal areas such as Mangaluru prefer marine fish even if it is much more costly than the freshwater variety.
A kilogram of the marine fish Pomfret costs about Rs 650 to 700 and the marine Sear fish could get as expensive as Rs 1,200 a kg.
The cheapest marine fish, Sardine now costs about Rs 160/kg. In comparison, freshwater species such as Rohu and Catla can be bought at Rs 160. But the big picture is this: The consumer has greater choice, a factor that has boosted fish consumption in the city. All the more reason for the fish to be fresh and hygienic, not a health hazard!