21053
Once the method had been validated , free MCs were determined in fish ( tench , T . tinca ) and crayfish from different ponds in order to understand how they are bioaccumulated through the food web .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None