Imperial ponds: A case study

Authors: Chase Ehlo

Year: 2012 (xliv)

Abstract

The Lower Colorado River Multi-Species Conservation Program (LCR MSCP) is a 50-year conservation program intended to address the biological needs of at least 26 species through implementation of its Habitat Conservation Plan. A component of the program is to develop off-channel locations focused on maintaining razorback sucker, Xyrauchen texanus and bonytail, Gila elegans genetic stock. In 2007, six ponds were established on Imperial National Wildlife Refuge, Arizona, and stocked with razorback sucker and bonytail. We carried out pond monitoring from 2007 to 2012 and focused on bonytail and razorback sucker abundance, growth, reproduction, and recruitment, and on habitat associations of resident razorback sucker. The project has had failures and successes. An adequate clean water supply and ponds devoid of non-native fishes have yet to be established. Despite this, both razorback sucker and bonytail survived, reproduced, and recruited in 2008 and 2011 in two of the six ponds. Although recruitment in 2008 was not properly estimated, one juvenile razorback sucker and more than 100 juvenile bonytail were captured between late 2008 and early 2009. An estimated 135 razorback sucker and at least one bonytail recruited in 2011 in the adjacent pond. These events followed consolidation of all native fish into a single pond with no non-native fish except western mosquitofish. The two ponds with recruitment also had the highest annual adult razorback sucker survival rates estimated at 83% and 87%. In contrast, post-stocking survival for razorback sucker in two other ponds ranged from 9% to 22%. With infrastructure changes and proper management actions Imperial Ponds will become an important conservation area that contributes to the persistence and recovery of razorback sucker and bonytail.