The Amazon air-breathing fish Arapaima gigas (Pirarucu) is a threatened emblematic species of the Osteoglossidae family, recognized for its gigantism and prized meat both in South America and abroad. Despite its commercial potential, aquaculture of A. gigas has been constrained by challenges in achieving controlled reproduction in captivity. This report presents a series of studies aimed at advancing our understanding of A. gigas reproductive biology. First, to develop tools for identifying fish sex and assessing female maturation stages, we used an ureterorenoscope to examine and understand female gonadal anatomy. This enabled, for the first time, the development of the cannulation technique for in vivo analysis of oocyte maturation in A. gigas, and histological descriptions of oocytes from primary growth to ovulation. Subsequently, we monitored (year-round) ovary development in different captive broodstocks using cannulation, finding that females paired with males in earthen ponds reach final maturation but often fail to ovulate or synchronize with males. We then applied hormonal therapies in different trials, testing slow-release GnRHa implants (Evac) in single (Trial I) and double doses (Trial II), as well as intraperitoneal (IP) applications of GnRHa (Trial III), carp pituitary extract (CPE) and prostaglandins (Trial IV), to either stimulate reproduction in ponds or to attempt collection of eggs and semen. Although direct reproduction could not be observed in these different trials, slow-release GnRHa implants proved safer for A. gigas, while IP applications showed potential risks. In these trials, we evaluated the impact of therapies on plasma sex steroid levels, oocyte development, changes in fish color pattern, and nesting behavior. Additionally, the inclusion of Spirulina sp. in broodstock diets was found to improve oocyte quality (Trial V), with effects seen in oocyte color and lipidic index. Finaly, we recently demonstrated for the first time the feasibility of in vivo semen collection in A. gigas, providing a detailed description of spermatozoa using scanning and transmission electron microscopy (SEM and TEM). These findings provided novel tools for identifying fish sex and maturation stages, enabling hormonal therapy trials and offering critical insights into A. gigas reproductive biology. This lays the foundation for more effective approaches to controlling reproduction, advancing sustainable aquaculture and conservation efforts.