The association between distinct male mating strategies and gonopodium size in the Poecillidae family is a topic that has been suggested in several scientific papers and studies. However, many of these works merely acknowledge that there is likely a relationship between these factors, without having collected data across species as evidence. The purpose of our study is to provide physical and conclusive data testing the connection, or lack thereof, between male reproductive traits and behavioral modes of reproduction. We will take measurements of gonopodium size using collections of Poeciliid fish species. We will then test for an association between gonopodium traits and mating strategies using several species. The main reproductive modes that we will be using to categorize each species being studied are mating attempts by means of coercive force copulations, courtship display, or both. Following the analysis of our findings, we hope to be able to come to a conclusion if there is statistically significant evidence that supports the correlation between male gonopodium size and mating strategies. By doing so, this study will provide key insights into the behavioral ecology and evolutionary adaptations of male fish within the Poecillidae family.