GnRHa-induced spawning in cage-reared Atlantic bluefin tuna: An evaluation using stereological quantification of ovarian post-ovulatory follicles

TitleGnRHa-induced spawning in cage-reared Atlantic bluefin tuna: An evaluation using stereological quantification of ovarian post-ovulatory follicles
Publication TypeJournal Article
Year of Publication2011
AuthorsAranda, G, Aragón L, Corriero A, Mylonas CC, la Gándara FD, Belmonte A, Medina A
JournalAquaculture
Volume317
Issue1-4
Pages255 - 259
KeywordsBluefin tuna, Disector method, Fecundity, GnRHa, Induced spawning, Thunnus thynnus
Abstract

The effect of a delivery system (implant) loaded with gonadotropin-releasing hormone agonist (GnRHa) on the spawning performance in captive-reared Atlantic bluefin tuna (Thunnus thynnus) was assessed by means of stereological quantification of ovarian post-ovulatory follicles (POF). Among untreated control fish no follicles were observed at the oocyte maturation (OM) stage; in contrast, 10 of the 16 GnRHa-treated fish showed follicles containing migratory-nucleus oocytes and/or hydrating oocytes. Post-ovulatory follicles were observed only in three of the 14 untreated individuals examined, while all but one GnRHa-induced fish showed POF in the ovary. Nevertheless, when POF were present in the ovary, the amount of ovulated oocytes was not found to be significantly different among GnRHa-treated and untreated control fish, and wild spawners. The relative batch fecundity (eggs g-1 of body mass) estimated from ovarian POF counts were 109.62±28.36 (control group), 68.92±13.05 (GnRHa-treated group) and 83.47±15.63 (wild group). It was concluded that treatment with GnRHa implant stimulated OM and spawning in captivity, thus enhancing the reproductive potential of the broodstocks; however, there appears to be a limitation in the number of eggs maturing in each batch, and the spawn fecundity was not increased by the hormonal treatment. © 2011 Elsevier B.V.

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