40188
The Thames Estuary becomes brackish between Battersea and Gravesend , and the diversity of freshwater fish species present is smaller , primarily roach and dace ; euryhaline marine species such as flounder , European seabass , mullet , and smelt become much more common .
 Thames Estuary, Battersea, Gravesend
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Thames Estuary, Battersea, Gravesend