Role of Sex Ratio and Density on Fertilization Success of Intensively Cultured Endangered Woundfin

Woundfin Plagopterus argentissimus are a small, endangered cyprinid found solely in the Virgin River across Utah, Arizona, and Nevada. As of now, only three facilities culture Woundfin for conservation propagation purposes, but there is growing concern that current extensive culture protocols are not meeting the conservation recovery goals outlined in the Virgin River Resource Management and Recovery Program. The development of alternative rearing methodology, like effective intensive culture conditions, could help increase production to more effectively meet the conservation propagation needs for this species. Our goal was to assess the effect of different sex ratios and fish densities on reproductive success at indoor facilities. We measured fertilization success at three different sex ratios (1:1, 1:3, 1:5; female:male) and three different fish densities (0.05, 0.21, and 0.47 fish/L) in a laboratory setting. Sex ratio did not significantly affect fertilization success (P = 0.73). Fertilization was completely inhibited at a density of 0.05 fish/L, but there was no difference in fertilization success between the two other density treatments (P = 0.92). Our findings suggest that a density greater than 0.05 fish/L and a sex ratio of 1:1, 1:3, or 1:5 will likely enhance fertilization success. The results and conclusions of this paper provide valuable rearing information for the Virgin River Resource Management and Recovery Program and hatchery managers attempting to increase production of Woundfin in an intensive culture setting.