International Journal of Aquaculture, 2018, Vol.8, No.17, 127-136
134
agents. Similar induction trends were reported for other fish species including Senegalese sole (
Solea senegalensis
)
(Weber et al., 2009), and European seabass (
Dicentrarchus labrax
). The current results revealed that the recovery
durations were more different than sedation duration in response to different doses of anesthetics. Clove oil led to
longer calming duration for both species inducing complete sedation in about a minute for adults and juveniles
and recovery duration was longer than the recorded using the two other anesthetics. In contrast, higher anesthetic
doses resulted in similar or shorter recovery times in gilthead sea bream (
Sparus aurata
) and seabass
(
Dicentrarchus labrax
) (Mylonas et al., 2005). Although large difference in recovery times between MS-222 and
clove oil was reported and probably caused by the stimulatory effect of MS-222 on the respiratory system and
heart of fish resulting in increased respiratory and heart rate which in turn removes excess anesthetic, clove oil has
an inhibitory effect on the respiratory rate and a lesser ability to remove excess anesthetic from the fish’s system
results in longer recovery times (Keene et al., 1998). Clove oil consistently yields similar levels of physiological
disturbance and minimizes responses to external stressors to that observed with MS-222 (Cho and Heath, 2000;
Sladky et al., 2001; Wagner et al., 2003). More studies proposed that clove oil is an effective alternative for the
sedation of fish and may have several benefits over other methods including its low cost (Cooke et al., 2004).
Table 4 Dose response in
M. cephalus
and
S. aurata
to 2-Phenoxyethanol in respect to different stages (S) sedation, (R) recovery
Fish stage & species
S duration (min)
R duration (min)
Adult
Conc. 300 mL
-1
Conc. 350 mL
-1
Conc. 400 mL
-1
Conc. 300 mL
-1
Conc. 350 mL
-1
Conc. 400 mL
-1
M. cephalus
(Mean±SD)
1.020±0.047
0.810±0.033
0.690±0.087
0.715±0.023
0.901±0.039
0.931±0.024
P1≤0.001
0.033*
0.021*
0.021*
0.010*
P2≤0.001
0.036*
0.107
S. aurata
(Mean±SD)
0.916±0.037
0.803±0.033
0.613±0.023
0.779±0.025
0.913±0.024
0.955±0.130
P1≤0.001
0.11
0.015,8*
0.025*
0.017*
P2≤0.001
0.022*
0.221,0
Juveniles
Conc. 200 mL
-1
Conc. 250 mL
-1
Conc. 300 mL
-1
Conc. 200 mL
-1
Conc. 250 mL
-1
Conc. 300 mL
-1
M. cephalus
(Mean±SD)
0.89±0.02
0.77±0.04
0.60±0.03
0.82±0.07
0.91±0.03
1.00±0.08
P1≤0.001
0.08
0.02
0.11
0.089
P2≤0.001
0.03
0.088
S. aurata
(Mean±SD)
0.746±0.043
0.655±0.038
0.569±0.041
0.914±0.027
1.040±0.045
1.094±0.080
P1≤0.001
0.022
0.011
0.270
0.110
P2≤0.001
0.068
0.205
Phenoxyethanol can induce sedation in both species, however, more concentrations should be used to reach
complete sedation and lower recovery durations were recorded.
The quick induction, long recovery time and high recovery rate were obtained at concentrations between
0.25~0.50 mL
-1
of clove oil. The hematological indices in goldfish while clove oil was used up to concentration of
75 ppm, were not changed however using clove oil at 150 ppm concentration could increased RBC value after
24 h (Abdolaziz et al., 2011). This oil is equally effective against the catfish
M. vittatus
. So, clove oil is a
user-safe, eco-friendly and alternative to the chemical fish anaesthetic and can be used in the aquaculture practice
(Alam et al., 2012).
In conclusion, clove oil was the most effective anesthetic for juveniles and adults
M. cephalus
and
S. aurata
handling in addition to its low price. Accordingly, authors strongly recommend and encourage people working in
aquaculture and fisheries sector to routinely use it in fish handling. Anesthetics are important to assist in reducing
stress during fish handling , however, more appropriate protocols are still necessary.
Authors’ contributions
Both authors designed the experiment, collected data, and references then carried out the statistical analysis, while the corresponding
author was responsible of manuscript writing and editing. Both authors read and approved the final manuscript.
