The effect of temperature on embryo survival and development in pallid sturgeon Scaphirhynchus albus (Forbes & Richardson 1905) and shovelnose sturgeon S. platorynchus (Rafinesque, 1820)

Abstract

Summary The thermal response of pallid sturgeon Scaphirhynchus albus and shovelnose sturgeon S. platorynchus embryos was determined at incubation temperatures from 8 to 26°C and 8 to 28°C, respectively. The upper and lower temperatures with 100% (LT100) embryo mortality were 8 and 26°C for pallid sturgeon and 8 and 28°C for shovelnose sturgeon. It was concluded that 12–24°C is the approximate thermal niche for embryos of both species. Generalized additive and additive‐mixed models were used to analyze survival, developmental rate and dry weight data, and predict an optimal temperature for embryo incubation. Pallid sturgeon and shovelnose sturgeon embryo survival rates were different in intermediate and extreme temperatures. The estimated optimal temperature for embryo survival was 17–18°C for both species. A significant interaction between rate of development and temperature was found in each species. No evidence was found for a difference in timing of blastopore, neural tube closure, or formation of an S‐shaped heart between species at similar temperatures. The estimated effects of temperature on developmental rate ranged from linear to exponential shapes. The relationship for rate of development to temperature was relatively linear from 12°C to 20°C and increasingly curvilinear at temperatures exceeding 20°C, suggesting an optimal temperature near 20°C. Though significant differences in mean dry weights between species were observed, both predicted maximum weights occurred at approximately 18°C, suggesting a temperature optimum near 18°C for metabolic processes. Using thermal optimums and tolerances of embryos as a proxy to estimate spawning distributions of adults in a river with a naturally vernalized thermal regime, it is predicted that pallid sturgeon and shovelnose sturgeon spawn in the wild from 12°C to 24°C, with mass spawning likely occurring from 16°C to 20°C and with fewer individuals spawning from 12 to 15°C and 21 to 24°C. Hypolimnetic releases from Missouri River dams were examined; it was concluded that the cooler water has the potential to inhibit and delay sturgeon spawning and impede embryo incubation in areas downstream of the dams. Further investigations into this area, including potential mitigative solutions, are warranted.

Lethal Thermal Maxima for Age‐0 Pallid and Shovelnose Sturgeon: Implications for Shallow Water Habitat Restoration

“…The results from this study indicate no significant difference in thermal tolerances between pallid and shovelnose sturgeon, implying that both species occupy a similar thermal niche early on in ontogeny. This result agrees with the notion that pallid and shovelnose sturgeon utilize the same thermal niche as embryos (Kappenman et al ., ). Temperature is a critical component in determining the metabolic energy demand (Hanson et al ., ).…”

Upper lethal temperature of larval pallid sturgeon Scaphirhynchus albus (Forbes and Richardson, )

“…Experiments showed that larval pallid sturgeon have a greater tolerance for high water temperatures than newly fertilized pallid sturgeon embryos (Kappenman et al., ) and a similar upper thermal tolerance as juvenile Scaphirhynchus sturgeon (Kappenman et al., ; Hupfeld et al., ). Results from this experiment provide evidence that pallid sturgeon larvae acclimated to 22°C can withstand exposure to 28°C water for 7 days without a loss of equilibrium or mortality.…”

“…Extreme temperatures can lead to reduced metabolic function, delayed development, and direct mortality in fish (Harig and Fausch, 2002;Schultz and Bertrand, 2011). Alterations to thermal habitats have been identified as a mortality mechanism in Scaphirhynchus sturgeons (Kappenman et al, 2009(Kappenman et al, , 2013Phelps et al, 2010;Hupfeld et al, 2014). Anthropogenic alterations to rivers and tributaries in the Missouri-Mississippi River basin have created unnatural zones of cold and warm water that can act as ecological traps.…”

Broadening the Regulated‐River Management Paradigm: A Case Study of the Forgotten Dead Zone Hindering Pallid Sturgeon Recovery

“…Samples were collected on 19 and 20 June 2012 when water temperatures in the river were optimal for Pallid Sturgeon spawning and embryo survival (Kappenman et al 2013). Samples were emptied into an 18.9-L plastic container and dissolved oxygen (DO), temperature, pH, and unionized ammonia were measured using a YSI (Yellow Springs Instrument, Inc., Yellow Springs, OH) Professional Plus meter.…”

“…The transition zone habitat has been previously described by Thorton (1990). As in 2012, measurements were collected on 18 June when water temperatures in the river were optimal for Pallid Sturgeon spawning (Kappenman et al 2013). Transects within each habitat type were spaced approximately 1 km apart.…”