Final ARIS Data and Predation Event Recorder Data from Contact Point Experiments in the Sacramento - San Joaquin Delta

The Central Valley Project Improvement Act (CVPIA) has led to the implementation of a Decision Support Model (DSM) to assist in the prioritization of CVPIA restoration actions. The fall-run Chinook salmon DSM depends on a coarse-resolution salmon life-cycle model to predict the population benefits of different restoration actions and scenarios. One critical element of the life-cycle model is how to incorporate predation mortality during the juvenile rearing and outmigration portion of the salmon life-cycle in the Sacramento-San Joaquin Delta. Of particular importance to potential restoration activities, is the predation mortality that occurs in proximity to, and as a result of contact points between predator and prey fishes. A recent Literature review and meta-analysis of potential contact points in the Sacramento-San Joaquin Delta identified artificial lighting at night (ALAN) and submerged aquatic vegetation (SAV) as two contact points that have been found to influence predation elsewhere and warrant further study in this river delta (Lehman et al. 2019). Other contact points identified in this review that may affect predation of fall-run Chinook salmon juveniles included water diversions, docks, piers, scour holes, and rip rap; however, the literature on predator prey interactions associated with these contact points is lacking (Lehman et al. 2019). These datasets cover two different experiments in the Sacramento-San Joaquin Delta during spring 2019 from April - June. One experiment focused on artificial illumination and was a paired control impact study where new artificial illumination sources were introduced into the ecosystem. The other experiment relied on existing physical contact points (SAV, docks, pilings, bridges, and diversions) and assessed predation risk as a function of proximity to these points. Both experiments used predation event recorders to quantify relative predation risk and the ALAN experiment used Adaptive Resolution Imaging Sonar (ARIS) to quantify the density of large fishes (presumably predators) among light and dark treatments. Both experiments have been completed and the results of the ALAN experiment have been published open access in the Transactions of the American Fisheries Society (Nelson et al. 2020). The results of this experiment indicate that ALAN attracted large piscivorous fishes and predation risk increased with increasing ALAN intensity, especially late in the night. The other contact point study had limited replication; however, results indicate that distance to SAV may have a significant relationship with relative predation risk. Lehman, B. M., M. P. Gary, N. Demetras, and C. J. Michel. 2019. Where Predators and Prey Meet: Anthropogenic Contact Points Between Fishes in a Freshwater Estuary. San Francisco Estuary and Watershed Science 17(4). http://dx.doi.org/10.15447/sfews.2019v17iss4art3 Nelson, T. R., C. J. Michel, M. P. Gary, B. M. Lehman, N. J. Demetras, J. J. Hammen, and M. J. Horn. 2020. Effects of artificial lighting at night (ALAN) on predator density and salmonid predation. Transactions of the American Fisheries Society https://doi.org/10.1002/tafs.10286. https://afspubs.onlinelibrary.wiley.com/doi/full/10.1002/tafs.10286