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Evaluating the Genetic Purity of Western Slope Native Suckers
Evaluating the Genetic Purity of Western Slope Native Suckers

​​​​​Led By

Kevin Tho​mpson​, Jenn Logan

Study Area

Colorado River Basin

Project Status


Research Objectives

  • To characterize Colorado-wide genetic diversity and purity among native sucker populations.

  • To ensure proper geographic representation of each species of sucker in brood stocks at CPW's Native Aquatic Species Restoration Facility (NASRF) in Alamosa.

  • To determine whether CPW researchers and biologists are encountering hybrid suckers that appear pure and to gauge accuracy in identifying which parental species are involved in hybrid specimens.

Project Description

Flannelmouth and bluehead sucker populations have declined in recent years, prompting CPW to focus efforts towards protecting and enhancing existing populations of these ecologically important fishes. Both flannelmouth and bluehead suckers will hybridize with non-native sucker species introduced to the Western Slope, threatening the genetic purity of the natives. To combat this problem or to re-establish populations of the native suckers, CPW needs to prepare for the use of captive-reared fish, necessitating the establishment of one or more brood stocks for each species.

Therefore, CPW initiated a study to characterize the genetic purity and diversity of suckers from river drainages across Colorado. To do so, researchers and biologists collected genetic samples from pure suckers to establish reference populations with which future genetic specimens could be compared. Afterwards, hundreds more samples were collected from numerous locations around the Western Slope to assess which populations remain the purest and also to determine how genetically diverse the various populations are. Results from this study helped determine how many brood stocks of each species CPW should maintain at NASRF in order to appropriately represent the genetic diversity of wild populations.

At the time of sampling, collectors attempted to visually identify the species of each sucker and several photographs were taken. Some fish of each species and each hybrid combination were retained as specimens for archiving and future study, as well as for future training in identification. Each genetic sample was analyzed and assigned to species or species mixes for hybrids. Genetic identifications were then compared to field identifications to assess agreement.  ​

We discovered that biologists and researchers were quite accurate in identifying pure fish versus hy​brid fish; however, identification of which parental species were represented in hybrid fish was very challenging especially when more than two ancestral species were represented in hybrid fish.

​Video: Bluehead Sucker Spawning​

​A rare view of these beautifully colored Colorado native Bluehead Suckers showing spawning behavior in the Roubideau Creek drainage near Delta, Colorado. Shot by a BLM employee in May 2012, this is a sight rarely seen in Colorado because the water is usually much less clear during the runoff when these fish spawn. You will see several brightly colored males attending to a single, less colored female.