ABSTRACT. Circulating levels of estradiol, vitellogenin and prostaglandins could be references of oocytes quality in the aquaculture industry. This study evaluated the performance of 17β-estradiol (E2) and vitellogenin (Vtg) levels in plasma and prostaglandins in oocytes (PGE 2) during the reproductive period of Oreochromis niloticus in a commercial farm in Ecuador. Adults fish females were treated with estradiol-synthetic (ES) and tilapia pituitary extracts (TP) during 25 days. For quantification of E2 and PGE 2, an enzyme-linked immunosorbent assay (ELISA) was used, while for Vtg relative quantification a Western blot analysis was performed. Circulating E2 concentrations were different during the first week of follow-up (P < 0.05) resulting in different levels of Vtg per treatment (P < 0.05) affecting on gonadal growth. The ovaries had an asynchronous development, where the mature oocytes proportions were higher with ES and TP than control. Relative fecundity was different between treatments (P < 0.05), where TP generated 15.7 ± 5.8 oocytes per g of spawning female. Furthermore, concentrations of PGE 2 were different between treatments (P < 0.05). The information reported in this study will be useful to improve the reproduction methods and have some biological signals before ovulation in tilapia commercial culture.

Aquaculture is a productive activity in economic growth due to market productivity which supports many Ecuadorian communities. However, exotic species has been the basis of this activity without considering the endemic and mega-diverse component of Ecuador. On the other hand, current aquaculture systems use a lot of water, generating discharge of nitrogen and phosphorus, causing a negative impact on natural watersheds. The present investigation focused on the diversification of aquaculture production and environmental care, through the polyculture of tilapia and river prawn, in a Biofloc system, which allows reducing the use of water, space, and food, taking advantage of all the nutrients of the aquatic environment without generating pollutant residues, from a carbon-nitrogen ratio of 20:1. The research project was developed under laboratory conditions at 2.728 amsl, for 8 weeks in pre-breading stages. Two factors were established in the study: type of culture (monoculture and polyculture) and production systems (traditional and biofloc), with three replicates. In the Biofloc system, the environmental variables such as temperature, pH, and oxygen did not show any significant differences between treatments (p≤0.05), while conductivity and total suspended solids increased during the test, and the nitrification processes stabilized at day 28 with values of 0.06±0.01 and 0.35±0.09 ppm in ammonium and nitrite respectively. The bacterial load was higher in the Biofloc system (113.66x103 CFU/ml) with predominance of Bacillus sp. and Pseudomonas sp. The bioflocs showed greater volume in polyculture (17.62 ml/L) and 26% of protein. Under these considerations, the best productive performance was detected in the Biofloc polyculture with a total productivity of 142.86g/m2 (p≤0.05). Therefore, diversification of species, types and culture systems are viable for aquaculture in Ecuador, generating an interaction between the chemical and biological components, allowing productive processes to be sustainable.

Vitellogenin (Vtg) is a specific phospho glycoprotein used as an environmental and steroidogenesis biomarker in fish. The present study shows the techniques to isolated IgY anti vitellogenin (Vtg) in Cichlasoma festae fish. Vtg was purified from adult males previously treated with estradiol and isolated from blood plasma using ion-exchange chromatography. Subsequently, Lohmann Brown hens were immunized at different doses, including three antigen booster doses. At day 45 post-immunization, posture eggs were collected, and successfully optimized the extraction of anti-Vtg -IgY antibody. The purified antibodies were validated with SDS-PAGE, detecting heavy and light chains of 70 kDa and 30 kDa, respectively. Further, we developed ELISA to estimate the Vtg specificity. Commercial anti-Vtg antibodies of Dorada (Sparus aurata) were used as a control, and immunoglobulins Y were validated for native species by Western Blot. The IgY anti-Vtg obtained by local conditions can be successfully used for programs in environmental monitoring and reproduction control in native aquatic species in Ecuador.

Native cichlids in Ecuador are represented by Andionoacara rivulatus and Cichlasoma festae mainly. These aquatic species are a fundamental part of the food chain of rural communities in the western subtropical region of Ecuador. For the first time, a detailed study on the gonadal development in A. rivulatus males and females was carried out, and the characterization of sex hormones present in their blood plasma from May 2019 to January 2020. Fish samples were captured in the multipurpose Baba River dam upstream of the Guayas River, Ecuador. Gonad and blood samples were collected for histological analysis and assaying of steroidal hormones such as 17β-estradiol and 11-ketotestosterone. The sex steroids were quantified by enzyme immunoassay (ELISA). As a result, the fish samples have asynchronous characteristics and show all development stages in testes and ovaries. The serological fluctuations show statistical differences (p <0.05) between the development stages, with low concentrations of estradiol and 11-KT. These results are somewhat related to the hydrological period of capture, where the temperature, luminosity, and rainfall play a fundamental role in the oogenesis and spermatogenesis in the captured fishes. The highest concentration of E2 is detected in female vitellogenesis stages and the highest concentration of 11-KT in the male spermatogenesis stage. These results confirm the fundamental role of these hormones in the key periods of gonadal development. In future studies, it is important to monitor the maturational hormone 17α, 20β-DHP, and the vitellogenin concentrations and thus understand the reproductive physiology of A. rivulatus.