Artificial induction of maturation in female silver eels, Anguilla australis: The benefits of androgen pre-treatment

11-Ketotestosterone dramatically affects ovarian physiology in previtellogenic eels, notably increasing lipid accumulation and the expression of the follicle-stimulating hormone receptor. We therefore sought to combine androgen pre-treatment of female silver eels with “traditional” hypophysation in order to assess whether androgens constitute a valuable addition to induced spawning protocols. Eels were first implanted with different doses (0-30 mg) of 17-methyltestosterone to evaluate effects on oocyte size. Females (Trial I) were subsequently subjected to repeated injections with carp pituitary homogenate to artificially induce maturation. In a subsequent trial, we used 1 mg of androgen, implanted in either aromatizable (androstenedione) or non-aromatizable form (11-ketotestosterone) and again induced eels to mature artificially by repeated injections with carp pituitary homogenate. Androgen treatment significantly increased oocyte diameters prior to commencing carp pituitary homogenate treatment. Thereafter, less time, less money and less handling were required to reach the pre-ovulatory stage, while retaining comparable amounts of lipid in ovulated eggs. We contend that androgen pre-treatment has promise as a synchronizing and cost-effective measure for the artificial induction of maturation in anguillid eels.