Hormonal treatment for reproduction in Latin American freshwater fish aquaculture

FATSINI, E., BATLOUNI, S.R., ELISIO, M., SANCHES, E.A., VISSIO, P., NÚÑEZ, J., DUNCAN, N.J., MECHALY, A.S.

Funchal

Congreso; Aquaculture Europe 2021; 2021

european aquaculture society

The rapid population growth in the world is generating significant challenges in supplying high-quality dietary fatty acid and protein. Aquaculture is the fastest growing food production sector that is widely recognized as an important part to solve the challenge (FAO, 2020). Latin America (LA) and the Caribbean show a lower growth in aquaculture production compared to other regions, and have mainly produced exotic species, Nile tilapia, Oreochromis niloticus; carp, Cyprinus carpio and rainbow trout, Oncorhynchus mykiss. Currently, Nile tilapia culture is the flagship of production in many LA countries, however, diversification into native species is desirable to meet market demand and increase both production and consumption of fish in the region. The round fish (tambaqui Colossoma macropomum, pacu, Piaractus mesopotamicus, pirapitinga, Piaractus brachypomus) and their intergeneric hybrids represent the native freshwater species group after tilapia with the highest production in LA. An important aspect to encourage the aquaculture production of these and other native fish species is to achieve and improve their reproductive control in captivity conditions, for which the hormone induction of spawning is a key strategy. Thus, the aim of this study is to summarize and highlight the most common reproductive problems detected in LA freshwater aquaculture sector and identify solutions for the region, based on hormonal treatment. Material and MethodsThe present study was conducted by analysing the considerable knowledge base gathered not only from indexed scientific publications, but also from a large amount of grey literature and aquaculture specialist?s comments in the considered region. This assessment arose in the frame of the Project LARVAplus, which has provided a space to exchange knowledge and experience for the benefit of the LA aquaculture industry development. Particularly, this study has compiled all information currently available about the use of hormonal treatments to control LA native freshwater fish reproduction. A special emphasis was given to the specific role of each hormone across the brain-pituitary-gonad axis. Results and discussionFish reproduction has been controlled in several native LA species; however, most of them presented reproductive dysfunctions, i.e., problems in the oocyte maturation, ovulation, and spontaneous spawning in females and in spermiation with a reduced volume and quality of milt in males. The injections of carp pituitary extract (CPE), a technique developed in the 1930s (von Ihering, 1937), was the most common treatment used in the different fish assessed resulted effective to induce viable spawning. The CPE is previously diluted in saline solution and then applied intramuscularly in the dorsal region for leather fish or at the base of the fins (usually pectoral) for scales fish. The CPE dose ranged between 2.0 to 5.5 mg/kg, applied by a single injection, 2 injections at 12h interval (curimba, Prochilodus lineatus and tambaqui), or up to 3 injections at 18h intervals (Sailfin Pim, Leiarius marmoratus). These changes in CPE doses and application forms are related not only to the inter-specific differences in the technique efficiency, but also to modifications of protocols based on criteria among different laboratories. Although the subject is still little explored in these species, ovulation is achieved only in part of females induced by administration of pituitary extract (PE). In females that failure to spawn after hypophysation, final maturation occurs but not ovulation; and this process has already been described in species like lambari, Astynax altiparanae (Roza de Abreu et al., 2020), pacu (Sato et al., 2020) and Leporinus friderici (de Souza et al., 2020). On the other hand, the use of synthetic Gonadotropin-releasing hormone analogue (GnRHa), has brought also good results (high ovulation and fertility rates), for instance in tambaqui (Souza et al., 2018). Although successful ovulation and fertilization was induced by GnRHa, high embryonic mortality was reported in many species after this treatment, as described for tambaqui, Leporinus macrocephalus (Pereira et al., 2017) and Leporinus friderici (de Souza et al., 2020). Finally, other hormones less studied, have been applied in some LA species, such as human chorionic gonadotropin (hCG), kisspeptins, among others. Hence, this study shows a detailed summary of the reproductive dysfunctions observed in the main native freshwater fish species produced in LA and the effects of the use of hormonal administration to improve reproduction. Finally, future research lines are necessary to improve LA fish reproduction in captivity. Recombinant gonadotropins technologies would be a goop option that offer the possibility to both induce premature maturation and earlier stages of gametogenesis in juveniles and control the reproduction of already adult fish.References: de Souza, T.G., Kuradomi, R.Y., Rodrigues, S.M., Batlouni, S.R. (2020). Wild Leporinus friderici induced spawning with different dose of mGnRHa and metoclopramide or carp pituitary extract. Anim. Reprod., 17, 20190078.FAO, (2020). Agriculture Organization of the United Nations. doi: https://doi.org/10.4060/ca9229enPereira, T.S.B., Boscolo, C.N.P., Moreira, R.G., Batlouni, S.R. (2017). The use of mGnRHa provokes ovulation but not viable embryos in Leporinus macrocephalus. Aquac. Int., 25(2), 515-529.Roza de Abreu, M., Silva, L.M.D.J., Figueiredo-Ariki, D.G., Sato, R.T., et al. (2020). Reproductive performance of lambari (Astyanax altiparanae) in a seminatural system using different protocols. Aquac. 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