Abstract
Breeding technology is of utmost importance for reproduction of wild fish in captivity for the reintroduction and selective breeding programs purposes. The main challenge is that when applied to wild undomesticated specimens, conventional protocols often cause breeders and/or embryo mortality and spawning failure. In this study, we evaluated the reproductive performance of wild Leporinus friderici, a great importance fish for subsistence fishing in South American rivers, applying conventional and lower-dose hormonal therapies by means of two consecutive experiments. In the first, a conventional (0.5 and 5.5 mg/kg) and a lower carp pituitary extract (CPE) dose (0.5 and 1.0 mg/kg) were applied. In the second, a conventional mammalian GnRH analogue associated with metoclopramide (mGnRHa + MET) (40 µg mGnRHa + 20 mg MET/kg) and a lower dose (4 μg mGnRHa + 2 mg MET/kg and 8 µg + 4 mg of mGnRHa + MET/kg) were applied. Ovulation was observed in all treatments, however, only lower CPE protocol provided viable embryos. High levels of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and 17β estradiol (E2) detected in conventional, but not in lower CPE dose, at ovulation, might be associated to the mortality of the embryos. The use of lower CPE dose applied here was the best way to obtain L. friderici viable embryos. These results directly contribute to the knowledge about poorly explored effects of reproductive management and hormonal therapies in wild-type breeders, showing that the use of reduced doses may be an alternative to reproductive success.
Highlights
Leporinus friderici is a medium size reophilic characiform fish native from South American rivers (Lopes and Leal, 2010)
The only one that generated viable Leporinus friderici embryos was the protocol with reduced doses of carp pituitary extract (CPE) (0.5 and 1.0 mg/kg)
Comparing to reduced doses of CPE protocol, the conventional CPE protocol (0.5 and 5.5 mg/kg) was more effective in promoting final maturation (GVBD), most of these oocytes remained retained in the ovaries, showing an imbalance between final maturation and ovulation
Summary
Leporinus friderici is a medium size reophilic characiform fish native from South American rivers (Lopes and Leal, 2010). According to the same report (IBGE, 2018), the group of fish known as piaus or piavas, which includes L. friderici, maintained a stable production between 2017 (3,801T) and 2018 (3,080 T). It is relatively recurrent in South American rivers, there are reports of reduction of natural stocks due to environmental degradation and predatory fishing (Andrade et al, 2005).
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