Seasonal floodplain‐tidal slough complex supports size variation for juvenile Chinook salmon (Oncorhynchus tshawytscha)

Abstract

Population diversity is a mechanism for resilience and has been identified as a critical issue for fisheries management, but restoration ecologists lack evidence for specific habitat features or processes that promote phenotypic diversity. Since habitat complexity may affect population diversity, it is important to understand how population diversity is partitioned across landscapes and among populations. In this study, we examined life history diversity based on size distributions of juvenile Central Valley Chinook salmon (Oncorhynchus tshawytscha) within the Yolo Bypass, a remnant transitional habitat from floodplain to tidal sloughs in the upper San Francisco Estuary (SFE). We used a generalized least squares model with an autoregressive (AR1) correlation structure to describe the distribution of variation in fish size from 1998 to 2014, and tested the effect of two possible drivers of the observed variation: (i) environmental/seasonal drivers within the Yolo Bypass, and (ii) the juvenile Chinook source population within the Sacramento River and northern SFE. We found that the duration of floodplain inundation, water temperature variation, season, and sampling effort influenced the observed time-specific size distribution of juvenile Chinook salmon in the Yolo Bypass. Given the lack of seasonally inundated habitat and low thermal heterogeneity in the adjacent Sacramento River, these drivers of juvenile size diversification are primarily available to salmon utilizing the Yolo Bypass. Therefore, enhancement of river floodplain-tidal slough complexes and inundation regimes may support the resilience of imperiled Central Valley Chinook salmon. K E Y W O R D SCalifornia Central Valley Chinook salmon, habitat complexity, hydrologic disturbance, phenotypic diversity, resource management, seasonal floodplain inundation | INTRODUCTIONPopulation diversity has emerged as an important mechanism for resilience in changing environments (Hilborn, Quinn, Schindler, & Rogers, 2003). For Pacific salmon (Oncorhynchus spp.), the link between increased spatial variation in habitat use and decreased interannual variation in production is apparent for both juvenile (Thorson, Scheuerell, Buhle, & Copeland, 2014) and adult life stages.These studies suggest that some aspects of population diversity are dependent upon the maintenance of a range of habitats (Carlson & Satterthwaite, 2011;Jonsson, 1988;Moore, McClure, Rogers, & Schindler, 2010;Schindler et al., 2010). The application of this concept has become increasingly important as we become confronted with potentially irreversible and cascading effects of climate change and other stressors (Battin et al., 2007). Further, hydrology is one of the major disturbance regimes thought to shape habitat conditionsThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations a...

Role of freshwater floodplain-tidal slough complex in the persistence of the endangered delta smelt

“…Third, the Yolo Bypass also experienced slightly warmer temperature between February and May relative to other regions of the estuary (Table 4), but so far, these temperatures have remained within the physiological limits of the species to support rapid growth [68]. The elevated temperature observed in the Yolo Bypass is likely due to the high residence time and shallow bathymetry of the region [17,39,40].…”

“…In coastal systems, floodplain wetlands can function as productive nursery habitats for fish exhibiting a diversity of life histories [10,11,12]. This nursery function stems from the shallow ephemeral nature of inundated floodplain wetlands, providing refuge from large predators and high densities of prey for rapid growth [8,9,13,14,15,16,17].…”

Managing for Salmon Resilience in California’s Variable and Changing Climate

“…For example, tidal inundation in Suisun Marsh generates warming and cooling patterns (Enright et al 2013) that may provide thermal refuges for fish. Similarly, on the Yolo Bypass, wind and topography generate different patterns of temperature variability than the adjacent Sacramento River (Sommer et al 2001;Goertler et al 2017). However, little of the targeted restoration in the Delta has yet been completed, and so results are lacking.…”

“…2003;Feyrer et al 2006;Sherman et al 2017 returning to spawn in their natal rivers-allows populations to diverge genetically, and to adapt to different stressors in different watersheds. Salmon from floodplain versus riverine habitats show the large phenotypic differences that can result from using different habitats (Goertler et al 2017). Given the significant loss of historical salmon habitat, a mosaic of aquatic habitats to support all stages would better allow California salmon stocks to withstand stochastic events and a changing climate.…”

Juvenile Chinook Salmon Weight Prediction Using Image‐Based Morphometrics

“…Additionally, size during this critical transition is one of the best predictors of survival for juvenile salmon (Unwin 1997;Duffy and Beauchamp 2011). Accurately assessing salmon morphology in different source waters, habitat types, and stages of outmigration informs our understanding of the regional and habitat specific contributions to life history models and can guide targeted habitat restoration and management actions (Carlson and Satterthwaite 2011;Goertler et al 2017).…”