Reproductive success of Bonytail chub in isolated off-channel habitats

Authors: Megan* Osborne, Alyssa Sanchez, Thomas Turner

Year: 2015 (xlvii)

Abstract

Bonytail is one of four species of large, long-lived, endemic fishes that were once abundant and broadly distributed throughout the Colorado River basin. Wild, naturally produced bonytail are now so rare that the species is considered functionally extirpated in the wild. Minckley et al. proposed using off-channel habitats to facilitate preservation of bonytail. In this program, native species would breed and their progeny would be allowed to grow in isolated, protected, off-channel ponds in the absence of non-native fishes. In 2014 and 2015 adult bonytail were stocked into three of the ‘Mohave backwaters’ and allowed to reproduce naturally. Microsatellites were used to identify the parents of larvae and age-0 bonytail produced in these backwaters, and to assess the change in genetic variability between the parental and progeny generations. Reproductive success was high for both sires and dams in both backwaters and both sexes mated multiply. In 2014, variance in reproductive success (VRS) differed dramatically between backwaters and this result was remarkably consistent between sires and dams, and where VRS was high, genetic effective size was reduced. In 2015, VRS did not differ between backwaters and hence effective size was similar between them.