Wohner,W.J, A. Duarte, J. Wikert, B. Cavallo, S.C. Zeug, and J.T Peterson. Integrating monitoring and optimization modeling to inform flow decisions for Chinook salmon smolts. Ecological Modeling
Monitoring is usually among the first actions taken to help inform recovery planning for declining species, but these data are rarely used formally to inform conservation decision making. For example, Central Valley Chinook salmon were once abundant, but anthropogenic activities have led to widespread habitat loss and degradation resulting in significant population declines. Juvenile Chinook salmon survival through the southern Sacramento-San Joaquin River Delta in particular, may be a limiting factor for juveniles outmigrating from the San Joaquin River and tributaries. However, survival and routing monitoring data have not been formally used to inform water management. Here, we illustrate how estimates derived from monitoring data can be used to inform water management and as a basis for developing adaptive management for flows. Specifically, we conducted a meta-analysis of Chinook salmon smolt survival and routing estimates through the south Delta. We then used the resulting parameter estimates to develop a survival and routing simulation model to estimate optimal flows for the San Joaquin River during smolt outmigration from February–May. We found that large flow pulses at predictable times during the spring are projected to be optimal for increasing Chinook salmon smolt survival to the Bay and that optimal scenarios differed somewhat with water year type. Sensitivity analysis revealed temperature and smolt outmigration timing are driving optimal pulse distribution and that water allocation changes little with parameter uncertainty. This case study highlights the utility of the decision-analytic framework for solving conservation problems.