of 0.33 g L−1 sodium carbonate and 0.75 ml L−1 glacial acetic acid
were sufficient to attain stage-4 anesthesia within 10 min. Beneficial qualities of this method are that it is harmless to the researcher
when used in an open area, inexpensive, portable in small plastic
containers, and can be easily disposed of with no anticipated environmental impact (Summerfelt and Smith, 1990). These positive
attributes, as well as the rapid induction time, enabled us to perform ovarian biopsies on adult red drum in the field without harm
to the investigators or the fish. Future studies may find the relationships we obtained relating size and induction time as helpful
initial guidelines, but for different species we recommend carefully evaluating how quickly the organism displays signs of stage-4
anesthesia prior to conducting formal research on the organism.
Investigators should also remain cognizant of the individual variability in induction time displayed within species and at a common
size.
We emphasize this work was not an attempt to examine physiological effects of carbon dioxide beyond short term survival and
concerns remain. For example, stress as indicated by cortisol levels may be elevated more by carbon dioxide than other anesthetic
methods (Trushenski et al., 2012a,b). Also, the brief exposure to
the reduced pH created by the addition of carbon dioxide may
have adverse consequences that require further research. Despite
these concerns, until more anesthesia options become available
(see Trushenski et al., 2013), carbon dioxide anesthesia is a satisfactory method. We conclude that sea water enriched with carbon
dioxide, made with sodium carbonate and acetic acid, can be a safe,
effective, and convenient anesthetic method for minimally invasive
surgery on marine fishes in the field.