Chemical and Electrical Approaches to Sedation of Hybrid Striped Bass: Induction, Recovery, and Physiological Responses to Sedation

Abstract

Currently, in the United States, there are few sedatives available to fisheries professionals that are safe, effective, and practical. Chemical sedatives, including tricaine methanesulfonate (MS-222), carbon dioxide (CO₂), benzocaine, and eugenol may be used to sedate fish, though none of these compounds are currently approved by the U.S. Food and Drug Administration as immediate-release fish sedatives. Another option is the use of electricity to temporarily immobilize fish. Few studies have assessed the efficacy of these options for immediate-release sedation in side-by-side comparisons. We evaluated the use of MS-222 (150 mg/L), CO₂ (∼400 mg/L), benzocaine (150 mg/L), eugenol (60 mg/L), and a commercially available electrosedation unit (30 Hz pulsed DC, 60 V, 25% duty cycle, 3-s exposures) to induce hybrid striped bass (white bass Morone chrysops × striped bass M. saxatilis; 510 ± 12 g [mean ± SE]) to stage IV anesthesia or sedation. Induction times were shortest (0.2 ± 0.1 min) when electrosedation was used and longest (2.5 ± 0.1 min) when CO₂ was used; the induction times for the other chemical sedatives varied (<2 min). Recovery times were longest for eugenol (5.2 ± 0.4 min postinduction) and benzocaine (4.0 ± 0.4 min); however, the difference in recovery time between these two treatments was not significant or between recovery times for benzocaine and the remaining sedatives (∼3–4 min). Physiological responses varied but were consistent with the generalized stress response. Circulating levels of cortisol, glucose, and lactate increased after sedation, and though response magnitude and duration varied somewhat among these variables, these changes were resolved within 6 h. Changes in plasma osmolality and hematocrit were less overt and varied less among the sedatives. Electrosedation may be a suitable tool for quickly sedating hybrid striped bass; however, all of the sedatives evaluated were effective at the doses and strengths used and some may be better suited to certain applications than to others.

Received April 5, 2011; accepted July 11, 2011

ACKNOWLEDGMENTS

We thank Smith-Root, Inc. for providing access to a Portable Electroanesthesia System (PES), and Jack Wingate and Mike Holliman for providing training and technical support in using the PES unit. We further thank Jack Wingate, Mike Holliman, and Carl Burger for providing a technical review of our draft manuscript. We also thank Kenson Kanczuzewski and Curtis Crouse for their assistance with data collection.