Diel Activity Patterns of Juvenile Late Fall-run Chinook Salmon with Implications for Operation of a Gated Water Diversion in the Sacramento-San Joaquin River Delta

Abstract

In the Sacramento–San Joaquin River Delta, California, tidal forces that reverse river flows increase the proportion of water and juvenile late fall‐run Chinook salmon diverted into a network of channels that were constructed to support agriculture and human consumption. This area is known as the interior delta, and it has been associated with poor fish survival. Under the rationale that the fish will be diverted in proportion to the amount of water that is diverted, the Delta Cross Channel (DCC) has been prescriptively closed during the winter out‐migration to reduce fish entrainment and mortality into the interior delta. The fish are thought to migrate mostly at night, and so daytime operation of the DCC may allow for water diversion that minimizes fish entrainment and mortality. To assess this, the DCC gate was experimentally opened and closed while we released 2983 of the fish with acoustic transmitters upstream of the DCC to monitor their arrival and entrainment into the DCC. We used logistic regression to model night‐time arrival and entrainment probabilities with covariates that included the proportion of each diel period with upstream flow, flow, rate of change in flow and water temperature. The proportion of time with upstream flow was the most important driver of night‐time arrival probability, yet river flow had the largest effect on fish entrainment into the DCC. Modelling results suggest opening the DCC during daytime while keeping the DCC closed during night‐time may allow for water diversion that minimizes fish entrainment into the interior delta. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

The effects of water temperature, acoustic tag type, size at tagging, and surgeon experience on juvenile Chinook salmon (Oncorhynchus tshawytscha) tag retention and growth

“…It is also one of the most effective methods to study the movement and survival of juvenile Chinook salmon (Oncorhynchus tshawytscha) out-migrating from freshwater rearing areas to the Pacific Ocean [13,32,36,53]. Other applications of acoustic telemetry include estimating the survival of juvenile salmon as they pass anthropogenic structures such as large water diversions [40] and understanding the migration routes through the California Delta [6,7,39]. These studies provide resource managers with valuable seaward migration survival data which are critical in making well-informed water management decisions [14].…”

Vitality models found useful in modeling tag-failure times in acoustic-tag survival studies

“…Acoustic telemetry is a powerful tool for studying fish movement and survival [9,16]. While many studies reasonably assume that tags do not fail during the study period [24,26], there are other studies with design limitations related to the size of the organism, duration of the study, and detection capability that make a degree of tag failure within a study unavoidable [2,33]. Under these circumstances, it becomes necessary to correct for tag life expectancies in order to make reliable inferences [8,35].…”

Vitality Models Found Useful in Modeling Tag-Failure Times in Acoustic-tag Survival Studies

“…Acoustic telemetry is a powerful tool for studying fish movement and survival (Jellyman 2009, Crossin et al 2017. While many studies reasonably assume that tags do not fail during the study period (Melnychuk 2010, Plumb et al 2016, there are other studies with design limitations related to the size of the organism, duration of the study, and detection capability that make a degree of tag failure within a study unavoidable (Adams et al 2012, Steig andHolbrook et al 2009). Under these circumstances, it becomes necessary to correct for tag life expectancies in order to make reliable inferences (Cowen andSchwarz 2005, Townsend et al 2006).…”