Technical Report
Spawning Periodicity of Rio Grande Silvery Minnow During 2012
Date: 2012/10/12
Author(s): Dudley R.K., Barkalow A.L., 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 2012 study was structured to monitor the temporal reproductive output of Rio Grande silvery minnow in the downstream-most river reach (San Acacia), where the majority of the population currently persists.
Sampling at the San Marcial Site was conducted from 30 April through 15 June (47 days). The cumulative volume of water at the San Marcial Site was 45,719 m3 . A total of 12,398 Rio Grande silvery minnow eggs was collected from 1 May to 26 May during 2012. Daily egg catch rates ranged between 0.17 and 466.71 eggs per 100 m3 of water sampled (n = 1 and n = 6,691 respectively). During the study, the overall egg catch rate at the San Marcial Site was 27.12 eggs per 100 m3 of water sampled. The number of eggs estimated to be transported downstream over the duration of the study was 12,471,939. The highest number of eggs estimated to be transported downstream in a single day was 5,619,124 (3 May 2012).