red drum and common snook in a covered, opaque plastic container (142 L “ice chest”) and opened the container approximately
every 15 s to monitor the level of anesthesia. Several stages of
anesthesia have been formally defined for fishes (Summerfelt and
Smith, 1990; Prince et al., 1995). At Stage 3, the fish exhibits
partial loss of equilibrium and increased opercular rate. At Stage
4, muscle control and equilibrium are lost and opercular movements are weak. We recorded induction time (in min) until Stage-4
anesthesia. We then measured total length (in cm; TL) and wet
mass (in g; WM) before returning the fish to oxygenated sea
water. We measured recovery time (min) as the time between
immersion in oxygenated sea water and return of equilibrium.
A single observer made all the timed observations to limit bias,
since assessing induction and recovery times can potentially be
subjective, as noted by Trushenski et al. (2012b). We verified 24-
h survival for red drum, flounder, and snook. In addition, most
flounder and all snook were maintained at our facility for at least
a month following experimentation. Other species were released
into the wild following recovery or euthanized as part of other
projects.
We define anesthetic effectiveness as achieving stage-4 with
induction time