Razorback and Flannelmouth Sucker Hybirdization

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Both hybridization and competition with non-native species pose a threat to the viability of the endangered razorback sucker. Ranges for both razorback sucker and flannelmouth sucker have been greatly reduced and both species are now confined to relatively small sections of the Colorado River resulting in overlap in timing and location of spawning. This has lead to hybridization between these two species. Understanding how hybridization may impact existing populations of razorback sucker will require information on egg viability and juvenile survival of hybrid individuals. Reliable means for differentiating hybrids from pure individuals in the field is needed. Hybridization has important ramifications for species definitions, listing status, and recovery of razorback suckers. We are proposing to investigate the egg viability, juvenile survival, and swimming ability of hybrids, as well as develop tools for field identification of young flannelmouth/razorback hybrids. Another threat to razorback suckers is low juvenile survival. Juvenile razorback suckers are found in shallow backwater environments of the Colorado River, where carp are the dominant fish. Razorback sucker and common carp occupy similar trophic positions and are often found in the same habitat. This suggests that competition with carp maybe negatively affecting razorback sucker growth and survival. We propose to investigate the effects of competition on the razorback sucker growth and survival in the laboratory using replicated artificial streams.

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