Biological and water quality monitoring of native fish sanctuaries in the lower Colorado River Basin, 2005-2009

Authors: Jeanette Carpenter

Year: 2009 (xli)

Abstract

The conservation plan for native fishes of the lower Colorado River (Minckley et al. (2003: Bioscience 53:219-234) recommends development of isolated, secure, off-channel habitats to be used in the recovery of native fish populations. We designed a monitoring plan to evaluate conditions of potential or current sanctuaries for razorback sucker (Xyrauchen texanus) and bonytail (Gila elegans). The goal of the monitoring protocol was to provide managers with information that will enhance success of established and future native fish sanctuaries. From 2005 to 2009, we monitored 13 sites. Biological data included mapping and identification of submerged vegetation; density and composition of zooplankton; presence of nonnative fish; and population structure, condition, and reproductive success of native fish. Physiochemical parameters included bathymetric mapping, chlorophyll, nutrients, temperature, pH, dissolved oxygen, conductivity, major ions, and trace elements (e.g., selenium). By September 2009, 11 sites had razorback sucker, bonytail or both: Cibola High Levee Pond, Davis Cove, Emerald Canyon Golf Course (3 ponds), Mohave Community College Pond, Needles Golf Course (2 ponds), Office Cove, Parker Dam Pond, and Three Fingers Lake. Two sites have no native fish: Bulkhead Cove and Palm Lake. In the sites with native fish, we found nonnative fish in 5 ponds: the Needles Golf Course ponds had Gambusia affinis and Lepomis cyanellus); two of the Emerald ponds had G. affinis), and Three Fingers has a suite of non-native species. We documented successful spawning and recruitment of bonytail at the two Needles ponds, at one Emerald Canyon Pond, and Parker Dam Pond, and both bonytail and razorback sucker at Davis Cove. Growth rates varied among sites. In late May, 2009, partial fish kills occurred at one Needles pond and one Emerald Canyon pond; the probable cause was low dissolved oxygen levels. The range of physiochemical and biological parameters varied considerably among sites that currently support growing or stable populations of native fish. We compared our data with a biological suitability model developed by Bio-West, Inc. in 2007; suitability scores from their model corresponded well with the variable success of our sites in providing native fish habitat.