The Effects of Water Temperature and Simulated Angling on the Physiological Stress Response of Largemouth Bass

Abstract

The Largemouth Bass Micropterus salmoides, a popular sport fish, is subjected to multiple sublethal stressors during angling, including high water temperature, exercise, handling, live‐well retention, and weigh‐in procedures. Combined effects of ambient and live‐well temperatures on the stress response and recovery from angling‐induced exercise have not been tested in conditions similar to those encountered in tournaments. Therefore, we assessed the effects of ambient temperature (17, 25, and 33°C) and live‐well temperature differential (−4, 0, and +4°C) on the physiological stress response of Largemouth Bass (mean length = 331 mm) at rest, following a simulated angling stressor, and throughout 8 h of recovery in live wells. Stress variables were measured in whole blood (hematocrit, hemoglobin, pH, partial pressure of oxygen [pO2], partial pressure of carbon dioxide [pCO2], Na+, K+, Ca2+, Cl−, and leukocytes) and plasma (cortisol, glucose, lactate, and osmolality). Fish acclimated to 17°C showed the greatest cortisol response after the chasing stressor; however, higher levels of glucose, lactate, pCO2, K+, and monocyte percentage were found at 33°C, and blood pH, Cl−, and lymphocyte percentage were lower at 33°C than at 17°C. When live‐well temperature was manipulated, cortisol levels were highest in fish subjected to the coldest conditions (acclimated to 17°C and retained in 13°C and 17°C live wells) and the warmest condition (acclimated to 33°C and retained in 37°C live wells). However, all fish subjected to the colder extremes survived, whereas 100% mortality occurred in the warmest condition. Besides cortisol, indicators of stress were less pronounced at colder temperatures. Glucose, lactate, and notably K+ concentrations were highest in 37°C live wells, and blood pH, Ca2+, Na+, and Cl− were lowest. Low blood lymphocytes and high monocytes at the warmest conditions indicate reduced immunocompetence or inflammation. Mortality at high temperature may result from exhaustion of aerobic and anaerobic energy sources, failure to recover from metabolic acidosis, and an inability to regain ionic balance.

Do live‐well additives influence the physiological and behavioral recovery of Largemouth Bass?

“…For recovery to occur, it is important for lactate to be reduced and muscle glycogen to be replenished (Girard and Milligan 1992). One means of recovery from exercise is via muscle glycogenesis, whereby blood lactate is converted back into glycogen via the glycolysis cycle (Dinken et al 2022). When an angling event occurs, glucose is mobilized into the bloodstream, supplying energy for aerobic tissues (e.g., brain and gills; Barton and Iwama 1991), which clearly occurred for the LMB retained in live wells for our study.…”

The effects of temperature and salinity on the blood chemistry and survival of juvenile Atlantic tarponMegalops atlanticus

“…Perhaps the most informative blood variable in this study was pH, which was highest at low temperature and low salinity but also elevated at low temperature and high salinity. Acid-base balance, which is indicated by blood pH, is extremely important to physiological processes, and extreme pH has been related to temperature effects on survival in other species (Dinken et al, 2022;Smit et al, 1981;Stewart et al, 2019).…”

“…Perhaps the most informative blood variable in this study was pH, which was highest at low temperature and low salinity but also elevated at low temperature and high salinity. Acid–base balance, which is indicated by blood pH, is extremely important to physiological processes, and extreme pH has been related to temperature effects on survival in other species (Dinken et al ., 2022; Smit et al ., 1981; Stewart et al ., 2019). Blood pH is known to generally relate inversely to temperature ( e.g ., decrease with increasing temperature) in water‐breathing and air‐breathing fishes (Cameron, 1978; Howell et al ., 1970; Rahn & Baumgardner, 1972).…”