| It was the condition that temperature 22.5±1.5℃,the mean total length of the newly hatched larvae of Mandarin fish was 3.73±0.10 mm(n=30) and the oval yolk sac was 1.316±0.153 mm3(n=30) volume,0.43±0.04 mm(n=30) in diameter.After hatched 12h, the tail fin of larvae was augmented and larvae could swim perpendicularly by tail swinging.The mean total length 2 day after hatched(DAH) larvae was 4.47±0.17 mm. Mouth was obviously to see and could open weakly.The larvae could swim ahead levelly, but it was slowly and weakly.At this period eyeball developed completly.The mean total length 4 DAH larvae was 5.36±0.38mm.The mouth velum of larvae disappeared and it was the first appearance of the mandible and maxilla.The digestive tract came into be two bends and the intestines put through.The ability of the level swim of the larvae enhanced and the larvae began to prey initiatively.It is determined that the larvae started the primarily.At the 6 DAH,the oval yolk sac and oil globule disappeared completely that the larvae quite get into exogenous feeding.The mean total length became 16.50±0.74 mm when 15 DAH.The mean increase rate of the larvae total length was 0.85mm/d in these 15 day period.The fin-rays of the larvae of 15 DAH had almost developed completely.At that time the surface form of the larvae was similar to the juvenile except the larvae without scale.In course of larvae developing,it was divided into three growth periods that the first was the endogenous feeding period with fast growth,the second was mixed feeding period with slowly growth and the third was exogenous feeding period with fast growth.According to equation TL=aD3+bD2+cD +d,making a correlation analysis between the total length and the DAHs of larvae,we found that the growth model of the Mandarin fish larvae was TL=0.0023 D3+0.0046 D 2+0.3041 D+3.8909(R2=0.9893,n=238).After preying normally in 4 DAH,the correlation equation between mouth width(MW) and total length was(TL) was MW= 0.0607TL+0.1743(R2=0.9215,n=162);the correlation equation between mouth hiatus(MH) and total length was MH=0.2067TL-0.0423(R2=0.9177,n=147).Both the mouth width and mouth hiatus were in direct proportion to the total length of the larvae.The Mandarin fish larvae usually prey in the dawn and dusk when it were at 06:00 and 18:00 in the week light.It were 4 days that Mandarin fish larvae had the prey ability from newly hatching to the point of no return(PNR) which determined that the larvae depend the exogenous feeding in a early time and starved endurance of the larvae was in a comparative low level.In the condition of temperature 24.5±1.5℃and pH:7.23±0.30,observing two different size larvae(each of the total length were 11.98±0.74mm and15.83±0.91cm) continuously for 24h,we found that the curve of two size larvae were similar in the change from day to night.The oxygen consumption in the afternoon was obvious lower than in the night,and both time appeared several similar maximal and minimum oxygen consumption.But the oxygen consumption 1.47mg/L和1.79mg/L of the different size larvae had obvious difference.In the conditions of the temperature 23.0±2.2℃,pH:7.01±0.25,according to the hydrobiology toxicity test,the acute toxicity test of Cupric sulfate(CuSO4),Chlorine Dioxide,Bromochlorodimethylhydantoin,Fenvalerate to the mandarin fish larvae were made.The result was that CuSO4 24h LD50 4.39 mg·L-1,48h LD50 3.33 mg·L-1,72h LD50 1.96mg·L-1,96h LD5 1.96 mg·L-1,the safe concentration was 0.20 mg·L-1;Chlorine Dioxide 24h LD50 8.75 mg·L-1,48h LD50 7.87 mg·L-1,72h LD50 6.14 mg·L-1,96h LD50 3.66 mg·L-1,0.37 mg·L-1;Bromochlorodimethylhydantoin 24h LD50 6.49 mg·L-1,48h LD50 6.31mg·L-1,72h LD50 5.25mg·L-1,96h LD50 4.80mg·L-1,the safe concentration was 0.48 mg·L-1;Fenvalerate 24h LD50 0.110 mg·L-1,48h LD50为mm,72h LD50 0.024 mg·L-1, 96h LD50 0.020 mg·L-1,safe Concentration was 0.002 mg·L-1。It indicated that the mandarin fish was more susceptive than the other fish.And Fenvalerate could not be used to cure the mandarin fish. |
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