Effects of the South Delta Agricultural Barriers on Emigrating Juvenile Salmonids

The TBP is implemented in compliance with the terms and conditions of two NMFS Biological Opinions (BiOp)
(NMFS 2008, 2009). To comply with the requirements of the NMFS BiOps, a study of the effects of the three
SDABs (i.e., ORTB, MRB, and GLCB) on emigrating (i.e., out-migrating) juvenile salmonids was conducted
(2010–2011) and the results are reported in this document. There were four effects considered in this study: 1)
survival of juvenile salmonids (Ŝ); 2) juvenile salmonid time-in-vicinity (TIV) of a barrier; 3) predation on
juvenile salmonids; and 4) predatory fish density evaluations near the barriers before-, during-, and after-
construction during each study year. For one barrier, the ORTB, two-dimensional (2D) acoustic fish tracks for
juvenile salmonids were used to evaluate: 1) the rates of successful passage through the barrier; and 2) route
selection through the barrier. In addition, utilizing the ORTB 2D fish tracks for both juvenile salmonids and
predatory fish, a mixture model (Romine et al. 2014) approach was employed to determine the probability that a
juvenile salmonid had been eaten by a predatory fish in the vicinity of the ORTB.