The knowledge and body size estimation of a prey item through undigested remains is important for the determination of prey's sizes selectivity by predator and understand these (predator-prey) interactions. Therefore, large size bones are used to perform these estimates, in part due to their resistance to digestion. The aim of this study is to determine the existence of bones with high correlation between them and body size in Eleginops maclovinus in order to estimate those parameters. Most of the measurements showed a highly significant correlation, but we decided only to work with the following bones: quadrate, suboperculum, cleithrum and maxilla because they showed the highest correlation coefficient. The length-weight relationship was: Weight = 0.041 Lt(2.597). We proposed that the selected measurements are suitable for morphometric analysis, and will help in a better understanding the predator-prey interactions, and potentially constitutes a good tool for studies of trophic relationship.