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Fish sedation facilitates safer handling of fish during scientific research or fisheries assessment practices, thus limiting risk of injury to fish and reducing stress responses. In recent years, there has been growing interest in using electricity to sedate fish; two methods include (1) lower‐voltage, non‐pulsed‐DC fish handling gloves (FHGs) that tend to only sedate fish while the gloves are touching the animal; and (2) a comparatively high‐voltage, pulsed‐DC Portable Electrosedation System (PES) that leads to galvanonarcosis. This study compared the physiological consequences of exposure to FHGs and PES in teleost fish. Bluegills Lepomis macrochirus and Largemouth Bass Micropterus salmoides were exposed to FHGs, PES, or a handling control for a 3‐min simulated surgery. Blood was then sampled at 0.5 and 4.5 h postexposure and was analyzed for blood glucose, blood lactate, and plasma cortisol concentrations. Opercular rates were monitored during surgery, at 2 min postsurgery, and 0.5 h postsurgery. At 24 h postsurgery, time to exhaustion (via a standardized swimming chase protocol) was assessed. Fish exposed to FHGs tended to exhibit lower opercular rates than fish that were sedated with the PES during simulated surgery. Cortisol levels of Largemouth Bass treated with FHGs were higher than those of fish sedated with the PES. Glucose levels recorded for Bluegills at 4.5 h postsurgery were higher with FHGs than with the PES. In both species, lactate was lower for fish treated with FHGs than for those treated with the PES. At 24 h posttreatment, Bluegills sedated with FHGs exhibited a longer time to exhaustion than those subjected to the PES, whereas Largemouth Bass sedated with the PES exhibited a longer time to exhaustion than those sedated with FHGs. Physiological responses to treatments were inconsistent between species. Further investigation to determine the optimal electrosedation method is required.
Environmental factors affecting growth of the threatened eastern sand darter ( Ammocrypta pellucida (Putnam, 1863)) were examined using specimens sampled from the northern edge of its range to determine the species’ critical habitat. Length-at-age increments were determined from scale samples as surrogates for growth rates based on back-calculated lengths using the Fraser–Lee method. During the first year of life, 82% of total length is attained, suggesting considerable energetic partitioning towards reproduction following age-0. Positive relationships between age-0 length increments and sand substrates and between age-0 length increments and mean annual channel discharge indicated greatest first-year growth within sand-dominated, high-discharge habitats. Environmental factors that occurred at coarse spatial and temporal levels (i.e., mean annual channel discharge) explained more of the growth variability among eastern sand darters than those occurring at fine levels (i.e., site-level substrate composition). This study indicates that environmental factors can be used to explain variability in cohort-structured population and site-level growth of eastern sand darters.
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