Thermal ecology of juvenile steelhead in a warm-water environment

Abstract

How salmonids adjust to the cost of chronic exposure to warm water in nature, particularly in habitats where areas of cold water are unavailable, is largely unknown. In the hot dry climate of southern California, oversummering juvenile steelhead, Oncorhynchus mykiss, can experience a continual warm-water environment. Studies were performed in three streams (34°N) during the summers of 2002-2004 to assess how steelhead (10-28 cm total length) exploit the thermal environment and to develop an understanding of how existing preference and heat tolerance information reported for the species relate to the actual temperatures the local population experiences. Analyses of achievable body temperatures, an index of observed body temperatures, and behavioral time budgets, indicate steelhead did not behaviorally thermoregulate. Findings from associated field surveys suggest areas of cold water were not available. Steelhead held focal points at temperatures (17.4-24.8°C) that were at times higher than the temperature preferences and heat tolerances reported for the species. Oversummering juvenile steelhead accept an elevated body temperature and remain active and forage throughout the day, apparently as a means for coping with warm water at the southern extent of their range. The relatively high body temperatures that steelhead accept appear to represent a compromise in exchange for maintaining an expanded geographic (latitudinal) range.

Climate change and fish culture in Patagonia: present situation and perspectives

“…In lacustrine populations of species such as Salvelinus alpinus or whitefish Coregonus lavaretus (L.), the consequences may be immediate if there is a limited scope for movement to deeper, cooler water (Graham & Harrod 2009), or if stratification, due to warming, results in oxygen depletion at depth (Wahl & Löffler 2009). This has proved to adversely affect exotic salmonids in Patagonia during the last 20 years (Aigo, Cussac, Peris, Ortubay, Gómez, López, Gross, Barriga & Battini 2008) in relation to relative abundances in littoral captures (Quirós, Cuch & Baigún 1986; Quirós 1991; Macchi, Cussac, Alonso & Denegri 1999; Macchi, Pascual & Vigliano 2007) and in agreement with data on thermal tolerances and preferences of O. mykiss (Spina 2007; Aigo 2010).…”

The Effects of Semichronic Thermal Stress on Physiological Indicators in Steelhead

“…The influence of food consumption on differences in lipids, growth increments, and hsp production was expected to be minimal because feeding was maintained at 2% body mass per day and food was consistently eaten except immediately after weighing and measuring (Deng et al 2009;Cassinelli and Moffitt 2010). Higher temperatures may cause decreased absorption of food during digestion (Bogevik et al 2011), though there is also evidence of minimal impacts on feeding and foraging behaviors in strains of thermally adjusted steelhead (Spina 2007). For the stock of steelhead used in these experiments, it is apparent that the level and duration of the thermal stress had an effect on their metabolism with resulting physiological consequences.…”

“…Temperature influences multiple levels of biological organization and dictates physiological processes such as metabolism (Brett 1979;Moyle and Cech 2004), protein synthesis (Kültz 2005), and growth in fish (Geist et al 2011). Salmonids, including steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) can be exposed to temperatures during summer months that exceed 25 • C when residing in streams (Matthews and Berg 1997;Spina 2007;Kammerer and Heppell 2013). This temperature exceeds U.S. Environmental Protection Agency standards for salmon-bearing streams (USEPA 2003), as it has been identified as a thermal limit for Rainbow Trout (Jobling 1981) and other salmonids (Dent and Walsh 1997;Geist et al 2010).…”

β‐Adrenergic Stimulation Enhances the Heat‐Shock Response in Fish

“…Temperature was increased 13Њ ‫ע‬ 1ЊC 3ЊC/h from 13Њ to 25ЊC. This heat-shock temperature was chosen because it is known to induce Hsps in fish rbcs and other tissues (Currie and Tufts 1997;Rendell et al 2006) and is an upper temperature now experienced by salmon and trout during the summer months (Lund et al 2002;Spina 2007). Fish then remained at this 25ЊC heat-shock temperature for 1 h and were returned to 13ЊC within 2 h after heat shock, as in the study by Rendell et al (2006).…”