HOWRAH: Hundreds of dead fish surfaced in Howrah’s Santragachi Jheel on Monday morning, leading to tension between residents of the area and police over the rights to the abundant catch. Even as the situation threatened to spill over, Jagachha police station deployed Rapid Action Force to disperse the 500-plus crowd that had gathered on the banks to grab the dead rohu , katla , tilapia and silver carp floating in the lake. Around 80 buckets of dead fish were finally buried in a pit to prevent being consumed or sold.While the conflict dominated the discourse on the incident, scientists, fish experts and a section of the administration pondered over what could have caused the deaths at the lake that draws a large number of migratory birds. Speculation that did the rounds ranged from poisoning by mischief-mongers to a drastic drop in the lake’s oxygen content due to a variety of reasons. Local environmentalists said they had never recorded deaths in such large scale at Santragachhi Jheel , though such incidents had been recorded at Rabindra Sarobar and the Botanic Garden lake.Ashish Bera, an electronics engineer who lives nearby, said he had spotted the odd dead fish floating in the lake for the past couple of days and had informed the Howrah Municipal Corporation (HMC) about it. Kartik Santra, another resident employed with the civic body, also claimed to have seen a few dead fish and alerted South-Eastern Railway (SER). But both the authorities were apparently reluctant to act. Though SER owns the land, the National Green Tribunal had asked the state forest department to oversee the maintenance of the lake. The forest department had reportedly passed the responsibility to the Howrah civic body.HMC added area development advisor Masood Alam Khan said water sample had been collected for examination. “This could be an act of mischief. The water appeared rather brackish. We will analyse it for contamination,” he said.Some also blamed SER, alleging water and oil from the carshed as well as a toilet block opposite the Santragachhi station ticket counter flowed into the lake, polluting it. However, SER chief public relations officer Sanjay Ghosh said the allegations were baseless as the railway, in compliance with the NGT ruling, treated the water and released it elsewhere. Fish expert Utpal Bhowmick felt the deaths could be due to methane and hydrogen sulphide released naturally or contamination by chemicals from detergents or other household cleaning agents. “Methane and hydrogen sulphide released from mass of submerged water hyacinth can lead to oxygen depletion. Excess carbon dioxide released by phytoplanktons on overcast mornings can also cause oxygen deficiency and deaths,” he said. Environmentalist Bonani Kakkar suspects pollution overload due to discharge of toxic chemicals from nearby buildings without proper treatment was responsible for the incident.HMC commissioner Bijin Krishna said the civic body was concerned about the fish deaths and looking into the matter. “The jheel was cleaned a few months ago. Some hyacinth was retained so that birds could perch and rest. The hyacinth has since grown. We may have to consider a comprehensive management plan,” he said.