Spatiotemporal Variability in Environmental Conditions Influences the Performance and Behavior of Juvenile Steelhead in a Coastal California Lagoon

Abstract

In California (USA), seasonal lagoons provide important oversummer rearing habitat for juvenile steelhead trout (anadromous Oncorhynchus mykiss). However, key water quality parameters such as temperature and dissolved oxygen concentration can periodically approach or exceed the physiological tolerances of steelhead during the protracted dry season. A field study employing distributed temperature sensing technology, water quality monitoring, habitat mapping, and mark-recapture sampling was conducted to examine how shifting environmental conditions affected the performance and behavior of juvenile steelhead in the Scott Creek estuary/lagoon (Santa Cruz County). Abiotic conditions were driven by episodic inputs of seawater to the typically freshwater lagoon. During midsummer, the water column was vertically stratified which reduced suitable lagoon rearing habitat by approximately 40%. Nevertheless, steelhead abundance, growth, and condition factor were high during the summer and decreased in autumn following lagoon destratification and cooling. Unlike previous work, this study identified limited emigration from the lagoon to riverine habitat during the summer. Instead, juvenile steelhead exhibited crepuscular movement patterns within the lagoon, with peaks in upstream (to upper lagoon habitat) and downstream (to lower lagoon habitat) movement occurring at dawn and dusk, respectively. This study underscores that habitat complexity and connectivity are critical for juvenile steelhead production and persistence and provides insight into steelhead habitat use and behavior in seasonal lagoons.

Consequences of Mouth Closure and Hypoxia-Induced State Changes in Low-Inflow Estuaries: Benthic Community and Trait-Based Response

“…On shorter time scales, Hadwen and Arthington (2006) reported that diversity and functioning of ICOLL communities in Australia were strongly influenced by entrance opening and closing regimes, with influence on diets of fishes and invertebrates. Mouth closure appears to reduce diversity relative to permanently open status (Pollard 1994b;Gray and Kennelly 2003), but there is conservation value to certain species associated with closed states (e.g., steelhead trout in Southern California) as well as temporally variable regimes of opening and closure (Watts and Johnson 2004;Hadwen and Arthington 2006;Bond et al 2022). For example, in the Carretas-Pereyra Lagoon (Mexico), which closes intermittently but is artificially opened for artisanal fishers (López-Vila et al 2021), there are half as many species reported as in a nearby permanently open lagoon (Gómez-González et al 2012).…”

Genetic divergence and one‐way gene flow influence contemporary evolution and ecology of a partially migratory fish

“…Variation in migratory strategy may have substantial implications for the density and size structure of O. mykiss populations and, by extension, the management and ecology of freshwater ecosystems. Migration to the marine environment and/or highly productive estuarine rearing habitat typically allows individuals to achieve larger body sizes at maturation compared to those that remain in freshwater (Bond et al, 2022;Hayes et al, 2008;Kendall et al, 2015). Given the positive relationship between body size and fecundity in O. mykiss and other salmonids (Quinn, 2018), the reproductive potential of resident and migrant ecotypes can differ by orders or magnitude (Hayes et al, 2008(Hayes et al, , 2012.…”

Complex temperature mosaics across space and time in estuaries: implications for current and future nursery function for Pacific salmon

“…For example, Sawyer et al (in press) estimated that estuarine growth improved marine survival by 31-47% for juvenile coho salmon (O. kisutch) on the Central Coast of British Columbia and that growth was substantially higher in a year with warmer temperatures. On the other hand, observations from an estuary lagoon in California suggest that excessively high estuary temperatures can limit rearing habitat and drive diel movements for juvenile steelhead and coho salmon (Osterback et al, 2018;Bond et al, 2022). Thus, navigating mosaics of temperature in estuaries and the associated growth opportunities can have important consequences for juvenile salmon during estuary rearing and seaward migration.…”