Effect of immersion treatment of soybean isoflavones extract on sex reversal in the Rainbow Trout (Oncorhynchus mykiss, Walbaum, 1792)

Abstract

This study explores the possible utilization of soybean isoflavones extract as potent alternatives for induction of sex reversal in the rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) with immersion treatment. Different concentrations (0, 0.10 and 0.20 g/L) of soybean isoflavones extract were tested for their effect on sex reversal in rainbow trout by immersing on newly hatched larvae twice for 1 months. The 14 days-old rainbow trout larvae (mean weight 0.123±0.03 g) were randomly removed from the hatching tank, and placed in 1000 L fiberglass tanks (200x100x75 cm). Each tanks comprised 1500 larvae and a total 4500 larvae were used for the experiment. When the fish reached four months, 50 randomly sampled fish from each group were sacrificed. For histological examination, the gonads were fixed in 10% neutral formalin and processed by routine dehydration and paraffin embedding procedures. At the end of experiment, the highest feminization (69.00±0.82%) was observed at 0.20 g/L soybean isoflavones extract treatment group. Morphological and histological examinations of the gonads in all groups revealed no intersex fish. Histological examination of fish treated with soy bean isoflavones extract revealed no damage to the testes or ovaries. In conclusion, these result indicate that the use of the higher doses of soybean isoflavones extract with immersion treatment can be effective for monosex rainbow trout population. ©Biharean Biologist, Oradea, Romania, 2019