Thermal Tolerance of the Piedmont Blue Burrower Cambarus harti and Sympatric Native and Invasive Crayfish Species of the Southeastern United States

Abstract

The southeast United States is the epicenter of global crayfish biodiversity, but these species are among some of the most threatened in the world. Life history and biological trait data deficiencies, particularly of burrowing crayfish species, hampers efforts for accurately assessing imperilment rates and informing conservation efforts. Rising temperatures are a threat to aquatic ectotherms and it is important to evaluate crayfish tolerances to determine if they are at or near their upper thermal limits. We conducted dynamic temperature ramps to evaluate the temperatures at which ecological death (critical thermal maximum; CTM) and physiological death (upper thermal limit; UTL) occurred for the imperiled and narrowly endemic primary burrower Cambarus harti and three common, sympatric species C. latimanus, C. striatus, and Procambarus clarkii. All species differed in CTM with C. latimanus being the most sensitive (35.0°C), C. striatus (37.0°C) and C. harti (37.8°C) having intermediate tolerance, and P. clarkii being the most tolerant (39.0°C). The UTL of all species ranged from 39.4 – 39.8°C. We found no evidence that C. harti, a rare primary burrower, will require more restrictive acute thermal guidelines for protection compared to more common sympatric secondary burrowers.