6536
In Group I , based on changes in the gonadosomatic index ( GSI ) and histologic observation of the ovary , the period from October 2008 through January 2009 was estimated to be the ' previtelline - forming period ' , February through March 2009 the ' vitelline - forming period ' , April through June 2009 the ' spawning period ' , and August 2008 the ' end of spawning period ' of the preceding year .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None