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- Enhancement of spermiation in meagre (Argyrosomus regius) using two administration methods of GnRHaPublication . Santos, Renata Fleck Pontes dos; Cabrita, ElsaReared – produced meagre (Argyrosomus regius) males (n=15) with 4 years old were monitored and sampled, during the reproductive season for spermiation, collecting sperm and blood 5 times on May 2016. The fish were treated with gonadotropin-releasing hormone agonist (GnRHa) injection and implant (EVAc). The fish were randomly allocated in three treatments, named Control (n=5), Injection (n=5) and Implant (EVAc) (n=5). The experiment on the enhancement of sperm production was performed using GnRHa injection and implant at 15 and 50 μg GnRHa mean weight kgˉ¹ dose respectively. During this time the fish were sampling at days 0, 2, 5, 12 and 19 after treatment and sperm and blood were collected. Sperm samples were evaluated for the sperm condition (arbitrary scale), initial sperm motility (min), motility percentage (%), spermatozoa density (cell/ml) and survival at 4ºC using the common method of analysis for sperm quality and the Computer-Assisted Sperm Analysis (CASA), a system that analyses and track each spermatozoa movement. The collected blood was centrifuged to separate the plasma in order to identify the steroid hormones testosterone (T), 11-ketotestosterone (11-KT) and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) using ELISA protocol. One fish per treatment was killed for histologic analysis in the last day of experiment. The obtained data from the common analysis of the sperm, CASA and the hormones were evaluated using a two-way ANOVA, with time (0, 2, 5, 12, and 19 Days) and treatment (Control, Injection and Implant) as the factors. GnRHa injection showed a short period of 2 days of effect regarding sperm production enhancement in meagre, while GnRHa implant proved to enhance the sperm production for a prolonged time. The results obtained for fish treated with GnRHa did not present statistical differences regarding the sperm quality parameters analysed both using the common methods of analysis and CASA. Furthermore, testosterone was the major steroid influencing spermiation. In conclusion, GnRHa implants seemed to be more appropriate to induce spermiation in meagre. Analysis of sperm should be conducted with accurate methods such as CASA.