Respiratory and Circulatory Responses to Hypoxia in Largemouth Bass and Smallmouth Bass: Implications for “Live‐Release” Angling Tournaments

Abstract

Arterial blood respiratory variables, ventilation rate, and cardiac output were examined in largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu to compare their physiological responses to graded levels of hypoxia. Reduction in water Po2 (Pwo2) from 150 to 45 torr (1 torr ≈ 133.3 Pa) caused similar decreases in arterial Po2 (Pao2) in both species, although total blood O2 content was markedly higher in largemouth bass at the lower oxygen tensions. Curves for in vitro O2 dissociation in normoxic fish indicated that largemouth bass blood had a higher affinity for O2 than smallmouth bass blood. Severe hypoxia caused a significant increase in blood concentrations of catecholamines in smallmouth bass but not in largemouth bass. Increases in ventilation rate (54%) and decreases in cardiac output (27%) during hypoxia were also more pronounced in smallmouth bass than in largemouth bass. Arterial blood pH did not change during hypoxia exposure in largemouth bass but decreased significantly during severe hypoxia in smallmouth bass. The results of this study indicate that smallmouth bass are more sensitive to hypoxia than largemouth bass are. These results have important implications for situations in which these two bass species may be exposed to periods of hypoxia, such as during live‐release angling events.

Effectiveness of Livewell Additives on Largemouth Bass Survival

“…Largemouth bass may recover from capture, handling, and livewell confinement stress if water quality is good (Furimsky et al 2003;Suski et al 2004), regardless of livewell additives. Although we did not find significant differences in delayed mortality among the livewell treatments, the consistent trend of higher mortality with livewell treatments during the field experiments suggests that additives may impart additional negative stressors that increase mortality.…”

Physiological tradeoffs may underlie the evolution of hypoxia tolerance and exercise performance in sunfish (Centrarchidae)

“…For example, the pumpkinseed sunfish [Lepomis gibbosus (Linnaeus 1758)] can tolerate deep hypoxia for longer periods than its congener, the bluegill sunfish [Lepomis macrochirus (Rafinesque 1810)] (Farwell et al, 2007;Mathers et al, 2014). Largemouth bass [Micropterus salmoides (Lacépede 1802)] also appear to be more tolerant of hypoxia than smallmouth bass (Micropterus dolomieu), as largemouth bass maintain higher blood O 2 content in hypoxia and can maintain blood pH at levels of hypoxia that induce a metabolic acidosis in smallmouth bass (Furimsky et al, 2003). Largemouth bass and smallmouth bass are generally good swimmers, with higher sustained swimming performance than both bluegill and pumpkinseed (Brett and Sutherland, 1965;Dahlberg et al, 1968;Kelsch, 1996).…”

Use of external Indicators to Evaluate Stress of Largemouth (Micropterus salmoides) and Smallmouth (M. dolomieu) Bass at Tournaments

“…Such collisions can result in dermal and ocular lesions, opening a vector for infections (a potential source of delayed mortality). Additionally, poor water quality and hypoxic conditions in livewells are often contributors to postrelease mortality during tournaments [8,13]. Lamprey wounding was rare in this study (< 2% of fishes), and the majority of fishes exhibiting lamprey wounds were smallmouth bass.…”

“…angling induced injury, barotrauma, or exhaustion) and delayed (within five days of angling) mortality. In numerous studies, high levels of angling or hauling (transport in a livewell or other enclosure) induced stress was linked to an increased likelihood of delayed mortality [8,9,15]. Mortality due to air exposure did not correspond to changes in blood chemistry among commercially captured Pacific halibut (Hippoglossus stenolepis) [10].…”

“…It is well documented that angling fish can have negative impacts on fish health and survival [5][6][7][8]. Stress levels can be influenced by a variety of factors including holding time *Address correspondence to this author at the Center for Earth and Environmental Science, SUNY Plattsburgh, USA; Tel: (860)859-7823; E-mail: galphonsemaynard@gmail.com [9], air exposure [10], livewell conditions [11], fish size [12], and water temperature [13].…”