The Effects of Semichronic Thermal Stress on Physiological Indicators in Steelhead

Abstract

The physiological response of juvenile steelhead Oncorhynchus mykiss to prolonged heat stress was examined by exposing replicated groups of fish to three different temperatures, 15, 23, and 25 • C, for 25 consecutive days followed by a 55-d recovery period at 15 • C. We found that at temperatures ≥ 25 • C, steelhead consumed significantly less food per day and had elevated feed conversion rates but experienced slower growth, reduced body size, lower body fat, and elevated heat shock protein (hsp) 70 levels relative to fish exposed to 23 • C and 15 • C. Growth decreased 24.4% and 27.1% for length and mass, respectively, between 15 • C and 23 • C, and an additional 60% and 56.5%, respectively, between 23 • C and 25 • C during exposures. While growth increments and lipid levels recovered to control levels after water temperature was reduced, body size of the fish exposed to 25 • C lagged throughout the experiment. Our results indicate a temperature threshold after which steelhead exposed to semichronic thermal stress incur a physiological debt. Heat shock protein 70 levels were detectable up to 25 d poststress in fin and liver tissues. This result provides evidence that hsp 70 is a useful metric for measuring thermal stress that can be assessed nonlethally and used to monitor thermal-habitat restoration efforts for threatened and endangered salmonids.

Effects of Diel Temperature Fluctuation on Growth, Stress Response, and Immune Function of Burbot

“…The lower feed consumption likely contributed to the differences in weight between the treatment and control groups, with the treatment fish weighing significantly less at the end of the experiment, similar to the lower growth at higher temperatures as reported by Kammerer and Heppell (2013b) and Selong et al (2001). The FCR results were comparable to those for steelhead exposed to thermal stress (Kammerer and Heppell 2013b), with higher values indicating less allometric growth per gram of feed. Our weight results were confounded by the SGR results, which indicated no difference between the groups.…”

“…The pattern of reduced food consumption at warmer temperatures has been seen in several species, including the Burbot (Hardewig et al 2004), Dolly Varden Salvelinus malma (Takami et al 1997), Whitespotted Char S. leucomaenis (Takami et al 1997), steelhead Oncorhynchus mykiss (Kammerer and Heppell 2013b), and Bull Trout S. confluentus (Selong et al 2001), and is potentially attributable to lower apparent digestibility at higher temperatures (Harwood 1979). The lower feed consumption likely contributed to the differences in weight between the treatment and control groups, with the treatment fish weighing significantly less at the end of the experiment, similar to the lower growth at higher temperatures as reported by Kammerer and Heppell (2013b) and Selong et al (2001). The FCR results were comparable to those for steelhead exposed to thermal stress (Kammerer and Heppell 2013b), with higher values indicating less allometric growth per gram of feed.…”

“…This is likely due to the different perfusion, clearance, and induction rates of different tissue types (Dyer et al 1991;Dietz and Somero 1993;Williams et al 1995Williams et al , 1996, with liver being more perfuse and having faster clearance than muscle. Other stressors have been shown to increase hsp70 abundance in fishes (Sanders 1993;Forsyth et al 1997;Wang et al 2013), but thermal stress has been of primary interest (Werner et al 2001;Cassinelli and Moffitt 2010;Kammerer and Heppell 2013b). Increased temperatures were shown to increase hsp70 expression in Atlantic Cod (Aursnes et al 2011) but without a measurable increase in hsp70 abundance (Zakhartsev et al 2005).…”

Climate vulnerability assessment for Pacific salmon and steelhead in the California Current Large Marine Ecosystem

“…Greater resilience in steelhead stems from several factors. First, steelhead inhabit streams warmer than those used by Chinook or coho salmon [61, 154, 155]. Compared to spring-run Chinook and sockeye salmon, steelhead also display greater mobility during migration, utilizing high-elevation, high-velocity, and hard-to-reach or ephemeral and intermittent stream habitats, as well as cool-water tributaries for temporary staging [156].…”

Acute Effects of Temperature, pH, and Suspended Solids on Antioxidant and Digestive Enzyme Activities and Stress‐Response Gene Expressions in the Boring Giant Clam Tridacna crocea

“…Antioxidant enzyme activities and stress‐response gene expressions are popular indicators that are used for evaluating animals’ stress response to environmental changes. For example, antioxidant enzymes (superoxide dismutase [SODs; enzyme number 1.15.1.1; IUBMB 1992], catalase [11.1.9], glutathione peroxidase [2.5.1.18], and glutathione transferase [2.5.1.18]) directly detoxify harmful reactive oxygen species (ROS) and other compounds that are induced by environmental stress (Yu 1994; Halliwell and Gutteridge 1999; Lushchak and Bagnyukova 2006; Kammerer and Heppell 2013). Molecular chaperones, such as heat‐shock proteins (HSPs), have general protective functions in response to oxidative stress (Parsell and Lindquist 1993; Feder and Hofmann 1999).…”