Intraspecific variation in metabolic rate response to temperature and salinity during early ontogeny in two estuarine species, C. Nebulosus and P. lethostigma




Hardin, Daniel


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The effect of temperature and salinity on marine teleosts is widely understood to act substantially in influencing physiological processes. In the face of climatic change and fisheries decline, understanding the effect of environmental factors on the larval life stage and recruitment success are of critical importance in maintaining effective marine conservation. In this study, metabolic rate was used to assess the metabolic rate response to short-term changes of temperature and salinity in two estuarine fish species, Southern Flounder, Paralichthys lethostigma, and Spotted Seatrout, Cynoscion nebulosus, sourced from parental sources from the North and South Texas coast along a temperature/salinity cline. Wild-collected broodstocks from each location were spawned in controlled conditions by the Texas Parks and Wildlife Department’s Stock Enhancement Program and offspring were reared under controlled conditions before being exposed to experimental treatments (C. nebulosus: 10, 28, 35, 45 psu; 28 °C. P. lethostigma: 20, 28, 35 psu; 14 and 18 °C). Larval routine metabolic rates varied significantly across salinity in C. nebulosus, though not between parental sources. Across both parental sources, C. nebulosus demonstrated a lower tolerance to high salinities at body masses of <1 mg, with no significant difference at larger body mass. The mass dependent metabolic response in C. nebulosus suggests limited tolerance to euhaline conditions post-hatch. The added factor of temperature in experiments with P. lethostigma was found to significantly interact with parental source and salinity, driving differences between larvae from the parental sources at 18 °C. Offspring from the Galveston Bay parental source showed significantly higher routine metabolic rate than those from the Aransas Bay parental source at 18 °C, with the opposite relationship suggested at 14 °C.



flounder, metabolic rate, physiological change, salinity, Spotted Seatrout, temperature



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