The purpose of this paper was to determine aspects of the reproductive biology of captively bred Fenneropenaeus merguiensis under commercial broodstock production conditions that relate to the design and implementation of genetic improvement programs for this species. First, we tested whether there is evidence for polygamy vs monogamy by genotyping females, the material found in their thelycums, and material that leaches out of the thelycum using DNA microsatellite loci. All genotypes in all animals and tissues tested could be accounted for using a monogamy model. Second we compared the accuracy of pedigrees formed under assumptions of monogamy vs polygamy. Pedigrees were formed using microsatellite genotypes from 73 dams and 400 offspring. Sibship groups and dam-offspring groups from pedigrees developed assuming monogamy almost always had the same mtDNA haplotypes, suggesting a high accuracy of the pedigrees, but those formed under the assumption of polygamy were less accurate, and together these results also support the monogamy model. Third, we assessed the between family variance in offspring family numbers from two sets of mass spawnings of about 40 inseminated females per spawn. About half of the offspring originated from just a few percent of the dams, i.e. many dams contributed few offspring. These data can help predict optimal sample sizes required for accurate future estimates of genetic parameters.