The Largemouth Bass Micropterus salmoides is the most sought‐after species by recreational and tournament anglers in the United States. Survival of angled and tournament‐handled Largemouth Bass has been related to numerous factors, but the independent effects of water temperature, angling time, and live‐well dissolved oxygen (DO) concentration on survival have not been measured. Understanding the independent effects of these factors on fish survival is necessary to formulate realistic models to predict population effects of catch‐and‐release and tournament angling throughout the year. Survival responses to water temperature, angling time, and live‐well DO concentration are also needed to develop guidelines useful for maximizing survival of released Largemouth Bass. Five‐day survival of Largemouth Bass larger than 300 mm was evaluated after simulated catch‐and‐release and tournament handling (8 h of confinement in aerated live wells and a weigh‐in before release) over the range of water temperatures typically encountered by Largemouth Bass anglers (17–33°C) while also testing independent effects of simulated angling time (1 and 3 min), live‐well temperature change (∆T = 0, −4, and +4°C), and live‐well DO (2.0, 5.5, and 8.5 mg/L). Survival of fish subjected to catch and immediate release was 100% at all temperatures measured, and survival of tournament‐caught fish was over 80% at temperatures of 29°C or less but declined at 33°C. Survival decreased with increased simulated angling time at high temperatures and at a DO level of 2.0 mg/L in live wells. Survival rates and probabilities provided in this study should be considered best‐case estimates because all fish were handled carefully and not subjected to hook wounding. However, results suggest that high survival of angled and tournament‐handled Largemouth Bass is possible with short angling times and appropriate live‐well management.

Advanced-sized Largemouth Bass Micropterus salmoides to be used for stocking and experimentation can be efficiently reared on prepared feed in intensive culture conditions, but formulated diets containing high levels (≥20%) of dietary carbohydrates may lead to high liver and muscle lipid and high liver glycogen levels, which may affect survival and stress responses. Largemouth Bass were raised to a size of 240-344 mm TL on formulated diets and then were fed live forage (i.e., naturalization); the effects of naturalization on liver, blood, and muscle health indices and physiological stress measures were evaluated, and indices were compared with those of wild Largemouth Bass from three different reservoirs. Hepatosomatic index (HSI) decreased by week 1 of naturalization; liver glycogen decreased by week 2; liver lightness, yellowness, and steatosis decreased by week 4; and liver moisture and lipid concentration stabilized after 4 weeks. Plasma cortisol was higher by week 1 of naturalization than by week 6 and onward, and plasma pH decreased after 1 week. Muscle color showed changes by week 1 of naturalization, muscle collagen stabilized by week 4, and muscle lipids decreased more gradually compared to the liver. The magnitude of stress response in fish subjected to a 60-s chasing stressor was unaffected by naturalization. Among populations of wild fish, many liver, blood, and muscle metrics were similar, with the exception of liver yellowness, glycogen, and HSI; muscle redness, lipids, and moisture; and the viscerosomatic index. Therefore, after rearing on a high-carbohydrate, high-lipid diet (i.e., 20% carbohydrates; 16% lipids), 4-6 weeks of naturalization can improve liver health, with most liver parameters being similar to those found in populations of wild fish.

Large numbers of advanced-size Largemouth Bass Micropterus salmoides needed for stocking and studies investigating the effects of environmental and angling stressors may be produced using formulated diets. However, fish reared on formulated diets can have lower survival than wild fish. Although survival can be improved by briefly feeding cultured fish a live fish diet prior to stocking (herein, termed naturalization), the time needed for pellet-reared fish undergoing naturalization to show improved and stable survival (i.e., to become naturalized) compared with pelletreared fish following a series of sublethal stressors has not been determined. Further, the difference in survival of pellet-reared, naturalized, and wild advanced-size Largemouth Bass following exposure to sublethal stressors has not been evaluated under controlled conditions. We conducted experiments to determine (1) the time required for pelletreared advanced-size (246-373 mm TL) Largemouth Bass to become naturalized following a series of sublethal stressors and (2) differences in survival of pellet-reared, naturalized, and wild advanced-sized Largemouth Bass subjected to two different series of sublethal stressors. Survival was high and did not significantly differ before (85%) and after 1-12 weeks of naturalization (90-100%). Survival was 100% for pellet-reared, naturalized, and wild Largemouth Bass following the series of sublethal stressors. We found no difference in survival among pellet-reared, naturalized, and wild Largemouth Bass challenged with a series of sublethal stressors. provided guidance on statistical analysis. This paper benefited reviews of earlier drafts provided by Wes Porak and three anonymous reviewers.

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.