Incorrect dosage of quicklime may have killed fish in Lapland

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An incorrect dosage of calcium oxide or quicklime, used as a disinfectant, seems the likeliest explanation for the cause of death of 16 tons of fish at a Kemijärvi fish farm on Wednesday.
      On the strength of samples taken on Thursday, superintendent Marko Kiviniemi of the Lapland Regional Environment Centre reckons that the pH-value in the fish tank had risen to a harmful level that was ultimately lethal to the fish.
      The cause of death of the fish will be officially confirmed in the next few days.
      At the Saarenputaan Lohi fish farm around six tons of powan (whitefish) and over ten tons of rainbow trout have died. The fish had just been moved from a river breeding tank to an inland winter tank to wait to be slaughtered for sale.
     
Managing director Markku Lassila of the fish farm, which has been in operation for a couple of decades, explains that for years quicklime has been used without a hitch to disinfect the inland tanks to prevent fish deaths.
      Lassila estimates that the accident has resulted in losses running to tens of thousands of euros. The fish were not insured. "Such insurance policies are not available in Finland because of the high risks involved in the business", Lassila says.
      Lassila confirms that the loss equals around 20 per cent of the company's annual turnover. The powan were to have gone for sale later this autumn, while the rainbow trout would have been processed next year.
     
According to Marko Kiviniemi, the accident does not cause a threat to the Kemijoki watercourse. From the winter tank, where the fish deaths occurred, water cannot enter the river. The Kemijärvi fire department has used oil booms to prevent the foam that leaked from the tank's outflow pipe from entering the Kemijoki River.
      The City of Kemijärvi Food Control confirms that fish bought from Saarenputaan Lohi on Wednesday or immediately prior to the accident is perfectly safe to eat. Samples that have been taken from the fish tank will nevertheless also be tested for possible fish diseases. This is the worst-case scenario, but current estimates suggest it is unlikely, and that pH values are the probable cause.
     
On Thursday, the pH value of the river water in the breeding tanks was 7.5, which is slightly higher than average. Kiviniemi attributed this finding to the dry summer and low runoff levels. The water in the affected winter tank, in turn, was strongly alkaline. Its pH value was over 11.
      Only one of the farm's several tanks was affected.


Previously in HS International Edition:
  Mass death of fish at farm in Lapland (5.10.2006)

Links:
  Calcium oxide (Wikipedia)

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