Induction of Fish Spawning Using Pituitary Extract from Lambari (<em>Astyanax altiparanae</em>)

This study evaluated the potential of lambari (Astyanax altiparanae) as a pituitary donor for hormone-induced spawning in fish. The effectiveness of the extracted hormone was demonstrated over four consecutive years, successfully inducing spawning in captive lambari as well as in two other rheophilic species, curimbatá (Prochilodus lineatus) and tambaqui (Colossoma macropomum). When administered in the same manner as crude carp pituitary extract, a total dose of 6 mg·kg⁻¹, divided into two applications (10% + 90%), proved to be effective, since spawning was obtained in the three tested species. Under the applied management conditions, donor fish maintained a gonadosomatic index of approximately 15%, with ovaries predominantly composed of mature vitellogenic oocytes. These females exhibited basal levels of estradiol (around 0.9 ng.ml-1) and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) (around 0.2 ng.ml-1), along with stable lhβ expression levels among different baths and between males and females. The lambari pituitary extract, when injected into females of the same species, induced a significant increase in 17,20β-P levels from approximately 0.2 to 1.0 ng·ml⁻¹. The use of lambari pituitary extract confirms that donor fish, both males and females, must be reproductively mature and in the breeding season. To our knowledge, most previous studies on extract donors are based on wild donors, making this one of the few that describe their physiological characteristics under aquaculture conditions. Low rearing densities seem to be crucial for obtaining a potent extract, although fish from the grow-out phase may also be suitable, a possibility that still requires evaluation. Our findings highlight the potential of lambari pituitary glands as a valuable alternative for hormone-induced spawning in small and medium-sized fish species, supported by their rapid maturation (4 months), low trophic level, increasing commercial production, and the prospect of using canned lambari to efficiently recover pituitary glands from fish heads.