Gonadosomatic index

{{Short description|Gonad mass as a proportion of the total body mass}}

{{Primary sources|date=April 2018}}

In biology, the gonadosomatic index (GSI) is the calculation of the gonad mass as a proportion of the total body mass. It is represented by the formula:{{cite book|last1=Anderson|first1=Richard O.|last2=Gutreuter|first2=Stephen J.|editor1-last=Nielsen|editor1-first=Larry A.|editor2-last=Johnson|editor2-first=David Lawrence|title=Fisheries techniques|date=1983|publisher=American Fisheries Society|location=Bethesda, Md.|isbn=9780913235003|pages=[https://archive.org/details/fisheriestechniq0000unse/page/283 283-300]|chapter=Chapter 15. Length, weight and associated structural indices|chapter-url-access=registration|chapter-url=https://archive.org/details/fisheriestechniq0000unse/page/283}}

GSI = [gonad weight / total tissue weight] × 100

It is a tool for measuring the sexual maturity of animals in correlation to ovary development and testicle development. The index is frequently used as reporting point in OECD test guideline, which may be used as indication or evidence of potential endocrine disruption effect of chemicals in regulatory framework (EFSA and ECHA, 2017). Guidance for the identification of endocrine disruptors in the context of Regulations (EU) no 528/2012 and (EC) 1107/2009. World Health Organization/ International Programme for Chemical Safety, 2002