TOXICITY OF 2-PHENOXYETHANOL AND PROPISCIN AS A NEW ANESTHETIC
FOR LARVAL SEA BASS DICENTRARCHUS LABRAX, L.
Jasna Maršic-Lucic
Institute of oceanography and fisheries, Split, Croatia - jmarsic@izor.hr
Abstract
Toxicity of two anesthetics, 2- phenoxyethanol and Propiscin, was examined on the larval sea bass (Dicentrarchus labrax, L.). Both
anesthetics showed low toxicity, Propiscin exhibited much lower LT
50
than 2-phenoxyethanol. Mortalities after 96 h were induced with
Propiscin at lower concentrations than for 2-phenoxyethanol. It can be concluded that 2-phenoxyethanol is a better choice for anesthesia
of larval sea bass.
Keywords: larval sea bass, 2-phenoxyethanol, Propiscin, toxicity
Rapp. Comm. int. Mer Médit., 37,2004
395
Introduction
The studies of anesthetic efficacy have been conducted mostly on
juvenile and adult freshwater fish, and little is known about the
toxicity concentrations for earlier life stages of fish, especially marine
ones (1). The goal of this study was to establish the toxicity
concentration of 2-phenoxyethanol and Propiscin when used for
anesthesia on larval sea bass, Dicentrarchus labrax.
Materials and Methods
Groups of 10 sea bass larvae were randomly put in glass aquarium
and the rest of 30 larvae were put in the control tank with aeration and
photoperiod of 12 h. Temperature, pH and salinity were measured
daily. A short-term bioassay was performed according to (2, 3). The
median survival time (LT
50
) was determined for each concentration of
test substance according (2,3). Differencies between mean survival
time (LT
50
) at the same concentrations were tested by ANOVA.
Larvae were exposed to 7 different concentrations (two replicates
per concentration) of Propiscin (0.2% stabilized solution of
etomidate) on logarithmic scale: 0.032, 0.056, 0.01, 0.18, 0.32, 0.56
and 1.00 ml/l, and to 5 different concentrations (two replicates per
concentration) of 2- phenoxyethanol on logarithmic scale: 0.18, 0.24,
0.28, 0.32, 0.56 and 1.00 ml/l.
Results
The average temperature, salinity and pH in vessels with 2-
phenoxyethanol was 18.5°C, 36.6 ‰ and 8.12. Fish weighted 0.39 ±
0,10 g. No mortalities were observed in both control tanks. At 0.032
and 0.056 mg/l concentrations no mortality was observed up to 96 h.
At 0.1 mg/l, 10% mortality occurred after 48 h, being zero for longer
time preiods. At 0.18 mg/l, mortality started after 36 h. At
concentrations higher than 0.32 mg/l, the mortality was 100% in the
first hour of the experiment. Because of the evident difference
between the mortalities related to the 0.18 and 0.32 mg/l
concentrations, two additional concentrations were tested, 0.24 and
0.28 mg/l (Fig. 1). The latter lead to 80% mortality in 96 h.
In tanks with Propiscin, the average temperature, salinity and pH
were 18.42 °C, 37,08 ‰ and 8.10. Fish weighted 0.33 ±0.09 g.
Propiscin induced mortalities at all concentrations. In first 1 h,
mortalities were observed for 1 and 0.56 ml/l. After 12 h, all fish died
at 0.32 ml/l (Fig. 2). In all cases, mortality was observed at times
<96h.
Discussion
Propiscin induced mortalities after 96 h at concentrations that were
non-toxic when fish were treated with 2-phenoxyethanol. The median
survival time at same concentrations of both anesthetics also differed
(F=0.775, d.f.1, P=0.389) with Propiscin having much lower LT
50
than 2-henoxyethanol pointing to its elevated toxicity for larval sea
bass.
Evaluated concentrations of etomidate for four different freshwater
fish show almost the same concentration range suitable for anesthesia
(4). For safe fish anesthesia, 2-phenoxyethanol is mainly used at
concentrations of 0.3-0.4 ml/l (5). Our results showed that the
concentration most suitable for anesthesia was 0.56 ml/l for Propiscin
and the most safe concentration of 2-phenoxyethanol was 0.32 ml/l.
The results showed that 2-phenoxyethanol was more suitable as an
anesthetic for larval sea bass than Propiscin.
References
1-Massee K.C., Rust M.B., Hardy R.W., Stickney R.R., 1995. The
effeciveness of triciane, quinaldine sulfate and metomidate as anaesthetics
for larval fish. Aquacult., 134: 351-359.
2-UNEP Manual, 1989. Test of the acute lethal toxicity of pollutants to
marine fish and invertebrates. Reference methods for marine pollution
studies, Monaco.No. 43, 27 p.
3-Reish D.J., Oshida P.S., 1986. Manual of methods in aquatic
environment research, Part 10 – Short-time static bioassays. FAO Fish.
Tech. Pap. Rome, FAO., 247, 62 p.
4-Plumb J.A., Schwedler T.E., Limsuwan C., 1983. Experimental
anaesthesia of three species of freshwater fish with etomidae. Prog. Fish-
Cult.,45(1): 30-33.
5-Woynarowich T., Horváth L., 1980. The artificial propagation of
warmwater finfish. A manual for extension. FAO Fish. Tech. Paper.,201:
138-147.
Fig.1.
Medial survival
time (LT
50
) at
different
concentration
(ml/l) of 2-
phenoxyethanol
on larval sea
bass.
Fig. 2.
Medial
survival time
(LT
50
) at
different
concentration
(ml/l) of
Propiscin on
larval sea
bass.
