| Trachinotus ovatus has very outstanding production and industry advantages.It is not only because of delicious,but also the short culturing cycle.In the same year of culturing,it can reach the commodity specifications and circulate in the market,which brings remarkable economic benefits and market prospects.At present,it has gradually become an important economic fish in China.In this experiment,the larvae of Trachinotus ovatus of 5.61±0.35cm were used as the research object.The effects of transport stress on water quality and the stress response of Trachinotus ovatus larvae were studied,which provided a theoretical basis for optimizing the transport parameters of Trachinotus ovatus larvae.The results of experiment 1 showed that the transport time was significantly correlated with the water quality and the survival rate of Trachinotus ovatus larvae(P<0.05).With the extension of transportation time,the ammonia nitrogen content in the water increases gradually and reaches the maximum value within 24 hours,which is 0.068mg/L.While pH decreased gradually with the extension of transportation time,and reached 6.81 at 24h.Temperature showed a trend of decreasing first and then rising.It reached the lowest value at 16 hours wasl 7.1? and the highest value at 24 hours was 26.1?.There was no significant change in dissolved oxygen concentration in water(P>0.05).When the transport time is less than 8 hours,the survival rate of Trachinotus ovatus larvae was 100%.But the transportation lasted more than 12 hours and the survival rate was gradually reduced to zero.It was determined that the optimum transport time of Trachinotus ovatus larvae is less than 8 hours.The results of experiment 2 showed that the survival rate of Trachinotus ovatus larvae with three different density groups(D1=9 kg/m3,D2=12 kg/m3,D3=15 kg/m3)had no significant effect,but had an effect on the water quality,the activity of immune enzyme and serum biochemical indexes.After 8 h of cryogenic,airtight,oxygenated transportation,the DO content of the transport water in the three density groups showed no significant change.The temperature and pH of the transport water decreased with the increase of the transport density,and the NH3-N content increased with the increase of the transport density.Among them,the content of NH3-N was significantly higher than that of the control group.In liver tissues,there was no significant difference in the t-sod activity of D1,D2 and D3(p>0.05),while there was a significant difference in the t-sod activity of D3 between the two groups compared with the control group(p<0.05).The LDH activity of the density transport stress group was significantly higher than that of the control group,and there was no significant difference between D2 and D3.There was no significant difference in POD activity among D1,D2 and D3 groups,but all of them were significantly lower than the control group.CAT activity of the three groups was significantly lower than that of the control group,and there was no significant difference between the three groups.In serum,the content of CRE in groups D1 and D2 was significantly lower than that in the control group,but the content of CRE in group D3 was significantly higher than that in the control group.Serum COR levels of Dl,D2 and D3 were not significantly different,but significantly higher than those of the control group.The content of GLU in D2 and D3 was not significantly different from that in the control group,while D1 was significantly lower than that in the control group.The activities of GPT and GOT in D1,D2 and D3 groups were significantly higher than those in the control group.Meanwhile,GPT activity in group D1 and D2 was significantly lower than that in group D3,but GOT activity was significantly higher than that in group D3.The suitable transport density of Trachinotus ovatus larvae is set to 15 kg/m3 within 8 hours of using cryogenic,airtight,oxygenated transportation.The results of experiment 3 indicated that the difference of eugenol concentration had an effect on transport water quality,survival rate,physiological and biochemical indexes of Trachinotus ovatus larvae.The control group had the highest pH and the lowest NH3-N,which were significantly different from those of the treatment groups(C1=5mg/L,C2=7mg/L,and C3=9mg/L)(p<0.05).With the eugenol concentration increased,the NH3-N increased in different degrees and the pH remained stable.The recovery rate in C3 was 80%which the other groups were 100%.There was no significant difference between control group and C1(p>0.05),the CRE content in other groups increased significantly with the increase of concentration(p<0.05).COR content increased first and then decreased,and was higher than the control group.In contrast with COR,GLU decreased first and then increased,both lower than the control group.The activity of GPT and GOT decreased first and then increased.Serum LDH and t-sod activity in the control group were significantly higher than those in other treatment groups(p<0.05).CAT activity of C3 group was significantly lower than that of other groups(p<0.05).POD activity increased with the increase of eugenol concentration.It is determined that the concentration of eugenol should not exceed 7mg/L within 8 hours of Trachinotus ovatus larvae under anaesthesia,cryogenic,airtight,oxygenation transportation.The results of experiment 4 showed that in the water quality of the three transport density groups(D1=27 kg/m3,D2=54 kg/m3 and 81 kg/m3),the pH value gradually decreased with the increase of transport density,and was significantly lower than that of the control group.The change of nll3-n shows a reverse trend.The lowest pH value and the highest ammonia concentration were found in the D3 group,6.24 and 0.08 mg/L,respectively.CAT activity in the liver increased gradually,but was still significantly lower than that in the control group.With the increase of transport density,POD activity in liver decreased gradually,but was still higher than that in the control group.Transport did not affect LDH activity in the liver.After 8 hours of transportation,the contents of GLU and CRE in serum of D1,D2 and D3 groups were all lower than those of the control group.The content of COR in serum soared,but the difference between Dl,D2 and D3 was not significant.Compared with the control group,the activity of GPT and GOT in serum showed a similar trend,that is,both showed a gradually decreasing trend with the increase of fish density.Transport density during transport significantly affeects water quality(e.g.,pH and NH3-N)and liver function.The transport density of Trachinotus ovatus larvae can be increased to 81 kg/m3 within 8 hours under anaesthesia,cryogenic,airtight and oxygenation.This study explored and optimized the transportations parameters of Trachinotus ovatus larvae,provides a scientific basis for actual production and logistics. |
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