Technical Report

Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

URL: https://webapps.usgs.gov/mrgescp/documents/SWCA_2007_Characterization%20of%20RGSM%20and%20Larval%20Drift%20Retention%20in%20the%20MRG.pdf

Date: 2007/04/01

Author(s): Widmer A.M., Kehmeier J.W., Fluder III J.J.

Publication: Report prepared for New Mexico Interstate Stream Commission, 42 p.

Abstract:

Artificial eggs (gellan beads) were used to characterize the retention and transport of silvery minnow eggs through the Albuquerque and Isleta reaches during spring 2005. This project occurred as three experiments, which quantified the retention of artificial eggs 1) between Angostura and San Acacia during high flow immediately following the arrival of a flood pulse (high flow ascending limb); 2) between Isleta and San Acacia at high flow without an ascending hydrograph (constant high flow); and 3) between Angostura and South Diversion Channel at low flow (constant low flow). These experiments enabled comparisons of egg retention between the Albuquerque and Isleta reaches under three flow conditions. Retention of artificial eggs was highest during the high flow ascending limb experiment, when inundation of floodplain areas and in-channel features would have been greatest (range 1.9% to 13.8% beads retained per km). Retention was 1.07 times higher in the Albuquerque Reach compared to constant low flow and 3.19 times higher in the Isleta Reach compared to constant high flow. Average egg retention rates were higher in the Isleta Reach than the Albuquerque Reach at all flows sampled. Egg retention was 4.78 times higher in the Isleta Reach than the Albuquerque Reach during the high flow ascending limb experiment; the magnitude of this difference was likely due to floodplain connection in the Isleta Reach.

Rio Grande silvery minnow distribution, as measured by catch per unit effort, appears to be roughly correlated with calculated bead retention rates. The majority of silvery minnow captured in the Isleta and Albuquerque reaches in April, May, and June 2005 were located in river kilometers 260 to 211, a section of the Isleta Reach that demonstrated consistently high rates of bead retention.