Statistical Analysis of Juvenile Salmonid Protection in California's Central Valley: Comparison of a Rock Barrier and a Non-Physical Barrier

An acoustic/strobe light/bubble barrier (Bio-Acoustic Fish Fence (BAFF)(Fish Guidance Systems, Southampton, UK)) exhibited significant overall efficiency for Chinook salmon juveniles at the Sacramento River/Georgiana Slough (SR/GS), California, Divergence in 2011 (88.7%) and 2012 (89.0%). At the SR/GS, the predation rates on Chinook juveniles in 2011 (3.5%) were similar to that in 2012 with BAFF On (2.6%). In 2009, Chinook juvenile overall efficiency (20.9%) at another site, the San Joaquin River/Old River (SJ/OR), California, Divergence, was not significant for BAFF On compared to BAFF Off; the associated predation rate with BAFF-On was 29.0%. In 2010, Chinook juvenile overall efficiency (35.5%) at the SJR site was not significant for BAFF On compared to Off; the associated predation rate was 21.7%. At least two factors contributed to these results: 1) there were higher predation rates at the SJ/OR site perhaps caused by a predator refuge immediately downstream of the BAFF at that location and 2) differences in the physical configurations.  In contrast, a rock barrier at the SJ/OR site in 2012 exhibited 61.8% overall Chinook juvenile efficiency; the associated predation rate was 38.2%. The factors leading to high overall efficiency are discussed including predation rates, physical configurations, and discharge regime.