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<br />THE USE OF ELECTRONARCOSIS AS ANAESTHETIC IN THE CICHLID, OREOCHROMIS MOSSAMBICUS. ill
<br />
<br />TABLE 4 The effects of 100 Vp rectified current electronarcosis at different frequencies on opercular recovery time, narcosis time and recovery time
<br />in O. mossambicus
<br />
<br /> Opercular Narcosis Recovery Narcosis
<br /> Length (cm) Mass (g) recovery time (s) time (s) coefficient
<br /> time (s) (s cm-1)
<br /> n= 8 8 8 8 8 8
<br /> Minimum 21,S 155,7 25,0 49,5 20,0 1,2
<br />~ Maximum 28,1 314,2 49,2 83,1 54,9 3,5
<br />Range 6,6 158,4 24,2 33,6 35,0 2,2
<br />0\ Mean 24,1 220,0 37,4 60,9 31,7 2,4
<br />VI
<br /> Standard Dev. 2,4 57,5 8,7 11,2 11,8 0,7
<br /> Standard Err. 0,8 20,3 3,1 3,9 4,4 0,2
<br /> n= 8 8 8 8 8 8
<br /> Minimum 21,0 155,0 17,2 69,9 11,6 2,9
<br />~ Maximum 27,7 355,3 48,6 169,0 64,9 7,6
<br />~ Range 6,7 200,3 31,4 99,1 53,3 4,7
<br />Mean 23,8 231,2 30,3 95,3 39,8 4,0
<br /> Standard Dev. 2,5 69,8 12,1 32,9 20,1 1,5
<br /> Standard Err. 0,9 24,7 4,3 11,6 7,1 0,5
<br /> n= 8 8 8 8 8 8
<br /> Minimum 19,3 1ll,8 15,6 35,8 15,6 1,4
<br />~ Maximum 27,5 323,4 31,8 108,4 207,4 4,4
<br />~ Range 8,2 211,6 16,2 72,6 191,8 3,0
<br />Mean 24,5 245,0 26,4 54,8 90,2 2,2
<br /> Standard Dev. 2,3 60,2 7,0 25,6 63,2 1,0
<br /> Standard Err. 0,8 21,2 2,5 9,0 22,4 0,3
<br /> 't' Values (df)
<br /> SOll00 (14) NS NS NS 2,800 (P=O,02) NS 2,510 (P=O,05)
<br /> 501200 (14) NS NS 2,786 (P=O,02) NS 2,574 (P=O,05) NS
<br /> 1001200 (14) NS NS NS 2,748 (P=O,02) 2,149 (P=O,05) 2,824 (P=O,02)
<br />
<br />df = degree of freedom; P = two-tailed probability; NS = not significant
<br />
<br /> 300
<br />"
<br />"0
<br />c: 250
<br />0
<br />u t
<br />~
<br />" f
<br />,!; 200
<br />~ f
<br />E
<br />j: 150 t
<br />" t
<br />'Uj
<br />0 100
<br />u
<br />OJ t
<br />z
<br /> 50 to' ,
<br /> .....
<br /> 0
<br /> 0 20 40 60 80 100
<br />
<br />Durallon 01 applied current In seconds
<br />
<br />FIG. 3 The effect of duration of current flow on the mean narcosis
<br />time (:t SEl in O. mossambicus subjected to rectified current
<br />electronarcosis
<br />
<br />that at 20 oC. This suggests that the relatively small dif-
<br />ference in mean lengths, as well as in the difference in
<br />mean mass, were probably not important factors in deter-
<br />minintil the different narcotizing effects observed at the
<br />two higher temperatures. Recovery times also followed a
<br />similar pattern with fIsh at the lowest temperature taking
<br />the longest time to recover. It must be noted that the
<br />optilnum mean narcosis time was at 15 oC. This phenom-
<br />enon can perhaps be related to the fact that this fIsh is a
<br />warm water species. .
<br />
<br />Effect of duration of application
<br />
<br />The results of an experiment to evaluate the effects of
<br />duration of application of a rectified current on O. mos-
<br />sambicus are given in Table 3 and illustrated in Fig. 3.
<br />These results are in general agreement with the results
<br />achieved in a similar experiment using alternating cur-
<br />rent (Barbanut aI., 1988)
<br />
<br />Narcosis time increased with application time up to 45
<br />s but, at 60 s application time, was significantly shorter
<br />
<br /> 2DO
<br />..
<br />"0
<br />c:
<br />0 150
<br />u
<br />~
<br />..
<br />,!; .'
<br />~ t .-~
<br />E 100
<br />j:
<br />.~ t f
<br />0
<br />u 50
<br />OJ
<br />z
<br /> 0 I I I I I
<br /> 0 50 100 150 200 250
<br />
<br />Frequency In Hertz
<br />
<br />,
<br />1
<br />[
<br />f
<br />
<br />FIG. 4 The effect of 100 Vp rectified current electronarcosis at differ-
<br />ent frequencies on the mean narcosis time (:t SE) in
<br />O. mossambicus
<br />
<br />(P = 0,01) than at 45 s. Further il}c~~s in application
<br />time up to 90 s resulted, once agam, m mcreased .narco-
<br />sis time, This trend is also apparent when companng the
<br />mean narcosis coefficients.
<br />Although application times of 75 and 90 s produced
<br />opercular recovery times which ranged from signifi-
<br />cantly longer (P = 0,02) to highly significantly longer
<br />(P = 0,(01) than shorter application times, there were no
<br />a'ppreciable differences between opercular recovery
<br />bmes at application times of 30, 45 and 60 s. ."
<br />
<br />Mean recovery times showed a seneral increase ~ith
<br />increasing application time, although there was consider-
<br />able variation witbina group. This intra-group variatio.n
<br />in recovery times appears to be common to all the expen-
<br />ments conducted in this study.
<br />
<br />Effects offrequency
<br />This particular aspect of the study was limited to 100
<br />Vp as t1ie apparatus confisuralion, using the a.c. ampli-
<br />fier was not able to produce higher potentials in the unit.
<br />
<br />C
<br />tI
<br />B
<br />
<br />70
<br />
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