Durability of environment-recruitment relationships in aquatic ecosystems: insights from long-term monitoring in a highly modified estuary and implications for management

Abstract

The environment can strongly influence the survival of aquatic organisms and their resulting dynamics. Our understanding of these relationships, typically based on correlations, underpins many contemporary resource management decisions and conservation actions. However, such relationships can break down over time as ecosystems evolve. Even when durable, they may not be very useful for management if they exhibit high variability, context dependency, or non-stationarity. Here, we systematically review the literature to identify trends across environment-recruitment relationships for aquatic taxa from California’s San Francisco Bay and Sacramento-San Joaquin Delta Estuary. This is one of the most heavily modified aquatic ecosystems in North America, and home to numerous species of concern whose relationships with the environment inform regulatory actions and constraints. We retested 23 of these relationships spanning 9 species using data that have accumulated in the years since they were first published (9-40 additional years) to determine whether they persisted. Most relationships were robust (i.e., same or stronger in magnitude) to the addition of new data, but the ability to predict how a species will respond to environmental change did not generally improve with more data. Instead, prediction error generally increased over time and in some cases very quickly, suggesting a rapid regime shift. Our results suggest that more data alone will not necessarily improve the ability of these relationships to inform decision making. We conclude by synthesizing emerging insights from the literature on best practices for the analysis, use, and refinement of environment-recruitment relationships to inform decision making in dynamic ecosystems.

Resistance and resilience of pelagic and littoral fishes to drought in the San Francisco Estuary

“…Increased frequency of drought in the future may lead to further decline or extinction of SFE‐endemic pelagic fish species such as delta smelt and longfin smelt (Hobbs et al 2017) and the proliferation of drought‐tolerant nonnative fish species commonly found in littoral habitat (Davis et al 2019). It is increasingly important for water management operations to optimize water release timing and location such that they balance human and environmental needs (Chen and Olden 2017), and to do so under an adaptive management framework (Tamburello et al 2019). Successful environmental flow management for species of concern would also require the proper consideration of other conservation measures such as habitat restoration, invasive species management, reduced contaminant loading, and climate change mitigation (Arthington et al 2006).…”

“…Increased frequency of drought in the future may lead to further decline or extinction of SFE-endemic pelagic fish species such as Delta Smelt and Longfin Smelt (Hobbs et al 2017) and the proliferation of drought tolerant non-native fish species commonly found in littoral habitat (Davis et al 2019). It is increasingly important for water management operations to optimize water release timing and location such that they balance human and environmental needs (Chen and Olden 2017), and to do so under an adaptive management framework (Tamburello et al 2019).…”

Fish Community Resistance and Resilience to Drought in the San Francisco Estuary: A Retrospective of Five Decades of Drought Cycles

“…However, California's water resources are scarce and an evergrowing competing demand for water lies in the future. It is increasingly important for water management operations to optimize water release timing and location such that they balance human and environmental needs (Chen and Olden 2017), and to do so under an adaptive management framework (Tamburello et al 2019…”

Ecosystem change as a driver of fish recruitment dynamics: A case study of two Lake Erie yellow perch populations

“…In fact, in his review of the fisheries literature, Myers (1998) found that few correlations between environmental conditions and fish recruitment held when they were re‐examined using new data. Despite this finding, environment–recruitment correlations are often used to inform the management of fish populations (Planque & Buffaz, 2008; Tamburello et al., 2019). Therefore, the use of analytical techniques capable of detecting changes in the importance of environmental conditions to fish recruitment is critical to better informing resource management.…”