Temperature and salinity preferences of endangered Delta Smelt (Hypomesus transpacificus, Actinopterygii, Osmeridae)

Hung, Tien‐Chieh; Hammock, Bruce G.; Sandford, Marade; Stillway, Marie; Park, Michael; Lindberg, Joan C.

doi:10.1038/s41598-022-20934-w

Cited by 12 publications

(7 citation statements)

References 55 publications

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“…Although Delta Smelt appear to adapt to acute salinity exposure both behaviourally and physiologically, Delta Smelt juveniles and sub‐adults show a preference for fresher water when given a choice between two options (Hung et al., 2022). Additionally, osmoregulation at higher salinities is thought to be energetically expensive for Delta Smelt.…”

Section: Discussionmentioning

confidence: 99%

Salinity and diel timing affect group structure in Delta Smelt

Chase,

Tsai,

Croshaw

et al. 2023

Aquaculture Fish & Fisheries

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Delta Smelt are thought to be on the precipice of extinction. Studies that examine how this endangered species responds to environmental change are important to informing conservation efforts. In the wild, Delta Smelt are likely to encounter wide variation in the salinity of their environment that is influenced by both natural and anthropogenic factors. We examined how salinity affects the group structure of Delta Smelt across multiple diel cycles. We found that the interaction between salinity (0, 5, 10 and 15 ppt) and time period (Day 1, Night 1, Day 2 and Night 2) influenced their spatial distribution within a group. Specifically, Delta Smelt were less dispersed, more cohesive and more homogenously distributed in saline water than in freshwater, but only on the first day, and this difference was not statistically significant. We also found that Delta Smelt were significantly less dispersed, more cohesive and more homogenous during the day than at night. Thus, Delta Smelt appear to behaviourally adapt to the initial stress of acute salinity exposure, which may mirror their physiological ability to acclimate to such conditions. Additionally, Delta Smelt group structure appears to shift depending on the time of day, suggesting that diel timing may influence conspecific interactions and should be considered in the experimental design of future studies. These findings further our understanding of how Delta Smelt behaviourally respond to environmental and diel variation.

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Section: Discussionmentioning

confidence: 99%

Salinity and diel timing affect group structure in Delta Smelt

Chase,

Tsai,

Croshaw

et al. 2023

Aquaculture Fish & Fisheries

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“…We used sub-adult Delta Smelt obtained from the UC Davis Fish Conservation and Culture Laboratory (FCCL; Byron, California) in each of the toxicity exposures. FCCL cultures a population of Delta Smelt which is annually outbred with fish collected from the wild, serves as a refuge population, and has recently been used to supplement the wild population (Fisch et al 2012;Lindberg et al 2013;Hung et al 2022)…”

Section: Delta Smelt Toxicity Testingmentioning

confidence: 99%

“…Although freshwater flows may benefit Delta Smelt, in the estuary these flows also contain varying concentrations and types of contaminants from industrial, urban, and agricultural sources (Thompson et al 2007;Smalling et al 2013;Orlando et al 2014;Jabusch et al 2018;De Parsia et al 2018;, resulting in the inclusion of the estuary on the Clean Water Act Section 303(d) and the 305(d) List of Impaired Water Bodies (SWRCB 2018). For instance, effluent from municipal wastewater treatment plants (e.g., Sacramento, Stockton, and Vacaville) and untreated stormwater runoff discharges into the Delta.…”

Section: Introductionmentioning

confidence: 99%

Sub-Lethal Responses of Delta Smelt to Contaminants Under Different Flow Conditions

Stillway,

Hammock,

Acuńa

et al. 2024

SFEWS

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The Delta Smelt is a largely zooplanktivorous, endangered fish endemic to the San Francisco Estuary (the estuary). High flows increase the availability of fresh and brackish water habitat for Delta Smelt, but also may mobilize contaminants, potentially increasing toxicological stress. Here, we examine the association between contaminants and Delta Smelt health across contrasting water year types and flow-related management actions. Our study spanned the fall season of three years: 1 dry year (2018) bracketed by 2 wet years (2017 and 2019) and coincided with several management actions meant to benefit Delta Smelt. We collected field water from six sites in the estuary that encompass the freshwater and low-salinity habitat of Delta Smelt and analyzed the water for contaminant concentrations. After a 96-hour exposure to the field water, we assessed cultured Delta Smelt survival and the histopathological condition of the gill and liver. Insecticides, particularly fipronil metabolites, were the most prevalent contaminants detected in 2017 and 2018, and a variety of contaminants associated with the rice harvest were detected in 2019. No acute toxicity was observed during any exposure, but we observed negative effects in the livers of Delta Smelt exposed to agricultural water from the Toe Drain and Cache Slough during a 2019 pulse flow action, which coincided with elevated detections and concentrations of organic pesticides. Other noteworthy sub-lethal effects, likely occurring in response to contaminant mixtures, included severe gill lesions in Delta Smelt exposed to Decker Island water in 2019. In the drier year of 2018, lesions were generally mild or absent. Thus, the trade-offs between increased habitat availability and contaminant loading may provide one explanation for why Delta Smelt abundance does not consistently respond positively to outflow.

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“…From Dec 2021 through Feb 2022, more than fty thousand adult Delta Smelt, raised at FCCL, were released into the SFE to evaluate survival, distribution and reproductive success for future supplementation to the wild population (Hung et al 2022). From Dec 2021 through Mar 2022, 75 of these sh were recaptured during routine agency sh monitoring trawls and con rmed to be of hatchery origin based on adipose n clips (hereafter 'supplemental sh').…”

Section: Application To Supplemental Delta Smeltmentioning

confidence: 99%

Liver glycogen as a sensitive indicator of food limitation in Delta Smelt

Dhayalan

Tran

Hung

et al. 2023

Preprint

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Assessing habitat quality is a major goal of conservationists and restoration practitioners, but to associate habitat quality with biomarkers of vagile animals, the biomarkers must respond rapidly. Here we identified a biomarker capable of rapidly detecting food limitation in the imperiled Delta Smelt (Hypomesus transpacificus), a pelagic fish endemic to the San Francisco Estuary (SFE). We conducted an experiment with fed and unfed treatments of hatchery-raised, sub-adult Delta Smelt that were sampled at 12 time points: 0, 1, 2, 3, 4, 5, 6, 7, 9, 11, 14, and 21 days. We then compared four biomarkers using Day 21 fish: RNA/DNA in liver, triglycerides in liver, glycogen in liver, and glycogen in muscle. Of the three liver endpoints, glycogen had the largest, most significant difference between treatments at Day 21, so we compared it to muscle glycogen across all time points. Liver glycogen declined after just one day of fasting and remained depressed in the fasting treatment across all subsequent time points. Muscle glycogen also responded rapidly, taking only two days to decline in the fasting treatment, but the difference was small and inconsistent across subsequent time points. When applied to hatchery-released Delta Smelt collected from the SFE, we found that liver glycogen concentrations were less than half that of the fed hatchery fish, consistent with the hypothesis of food limitation in the wild, but also several other potential causes. This study highlights the utility of biochemically determining liver glycogen concentrations of wild-caught Delta Smelt to provide insight into local habitat quality.

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Temperature and salinity preferences of endangered Delta Smelt (Hypomesus transpacificus, Actinopterygii, Osmeridae)

Cited by 12 publications

References 55 publications

Salinity and diel timing affect group structure in Delta Smelt

Salinity and diel timing affect group structure in Delta Smelt

Sub-Lethal Responses of Delta Smelt to Contaminants Under Different Flow Conditions

Liver glycogen as a sensitive indicator of food limitation in Delta Smelt

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