Vanessa Morales

Assessment of Fish Stress Levels Using Enzyme Lactate Dehydrogenase

Vanessa L. Morales, Jacob A. Gaskill, Katrina Knott, Rebecca O'Hearn, Darby Niswonger, Alba Argerich, Rebecca L. North

College of Natural and Applied Sciences, Missouri State University, Springfield, Missouri

School of Natural Resources, University of Missouri, Columbia, Missouri

Resource Science Division, Missouri Department of Conservation, Columbia, Missouri

Abstract:

The objective of this study is to identify which environmental factors have the greatest influence on fish stress levels. We hypothesize that fish stress levels will change with season, which to the best of our knowledge is the first of its kind, and with microcystin concentrations in the water. Free-range largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) were sampled from an agriculturally impacted reservoir with a history of algal blooms using diurnal boat electroshocking twice per season between April, 2018 and March, 2019. Microcystin levels during the sampling year ranged from below the detection limit (BDL: 0.15 mg/L) to 1.025 mg/L. We measured the enzyme Lactate Dehydrogenase (LDH) in fish tissues to assess fish stress levels. Higher or lower than average LDH values can indicate cell damage. Preliminary results reveal no clear relationship between LDH activity and microcystin concentrations in the water column. LDH activity in bluegill was higher (529.96 mu/mL to 18137.21 mu/mL) than largemouth bass (BDL to 16809.84 mu/mL). The presence of cyanotoxins in the water column did not result in elevated fish stress, however, due to high enzyme activity in the spring, we believe spawning may be a key stressor to the fish sampled. A next step would be to evaluate cyanotoxins levels in fish muscle to determine if that has a significant effect on fish stress. With information collected through this project, we can begin to assess what goes into stressing a fish, which is important for lake managers who want to create more recreational opportunities for anglers all around.