Publication Technical Report

Spatial Spawning Periodicity of Rio Grande Silvery Minnow During 2011

URL: https://webapps.usgs.gov/mrgescp/documents/Dudley%20and%20Platania_2011_Spatial%20Spawning%20Periodicity%20of%20RGSM%20During%202011.pdf

Date: 2011/11/23

Author(s): Dudley R.K., Platania S.P.

Publication: Prepared for U.S. Bureau of Reclamation, 42 p.

Abstract:

Systematic monitoring of the reproductive output of Rio Grande silvery minnow at multiple sites in the Middle Rio Grande was first conducted in 1999 and has continued annually (except 2005) since 2001. Previous studies demonstrated May and June as the primary period of spawning activity. The 2011 study was structured to monitor the spatial and temporal reproductive output of Rio Grande silvery minnow in the two downstream-most river reaches (Isleta and San Acacia), where the majority of the population currently persists.

Sampling at the Sevilleta Site was conducted from 19 April through 10 June 2011 (53 days) and at the San Marcial Site from 16 April through 10 June (56 days). The cumulative volume of water sampled at the two Rio Grande sites in 2011 was 222,290.1 m³ (180.2 acre-feet). The cumulative volume of water sampled at the Sevilleta Site was 131,533.3 m³ and the total amount of water sampled at the San Marcial Site was 90,756.8 m³ . A cumulative total of 120,280 Rio Grande silvery minnow eggs were collected at the two sites during 2011. The majority (n = 96,266; 80.0%) of the catch was taken at the San Marcial Site while the number and cumulative percent of Rio Grande silvery minnow eggs collected at the Sevilleta site was lower (n = 24,014; 20.0%). Daily egg catch rates at the Sevilleta Site ranged between 0.06 and 850.6 eggs per 100 m³ of water sampled (n = 1 and n = 12,198, respectively) while daily egg catch rates at the San Marcial Site ranged between 0.05 and 2,334.97 eggs per 100 m³ of water sampled (n = 1 and n = 34,129, respectively). During the study, the overall egg catch rates at the Sevilleta and San Marcial sites were 18.26 and 106.07 eggs per 100 m³ of water sampled, respectively. The number of eggs estimated to be transported downstream of the Sevilleta Site over the duration of the study was 25,113,808 with a daily maximum of 14,651,180. The number of eggs estimated to be transported downstream of the San Marcial Site over the duration of the study was 67,294,278 with a daily maximum of 27,420,356