Effects Of Three Transport Conditions On Short-haul Transport Of Hippocampus Erectus

Seahorses（Hippocampus erectus）are important aquaculture fish,and the transportation of their larvae is a critical process in production.Factors,such as water temperature and dissolved oxygen concentration,may have different effects on seahorse larvae during transportation,which largely determine the subsequent farming results.In this study,we used lined seahorse larvae as the research material and simulated short-distance transportation conditions to analyze the changes in seahorse survival,water quality parameters,activities of digestive enzymes,and antioxidant enzyme,etc.under three common transportation conditions with different oxygen concentrations,densities,and temperatures.The results provide a theoretical basis for establishing appropriate transportation techniques for seahorse larvae.The main results are as follows.1.As the transportation oxygen concentration decreased,there were significant differences（P<0.05）in water quality,survival rate,and physiological enzyme activity of lined seahorse larvae in the transportation water.（1）As the oxygen concentration decreased to 3.0mg/L,the concentrations of NH₄⁺-N and NO₂^--N in the transportation water significantly increased to 0.16mg/L and 0.012mg/L,respectively.（2）When the transportation oxygen concentration decreased from the normal concentration to3.0mg/L,the survival rate significantly decreased.（3）In terms of digestive enzymes,the activity of pancreatic protease and lipase in lined seahorse larvae significantly decreased,while the activity ofα-amylase significantly increased as the oxygen concentration decreased.（4）In terms of respiratory enzymes,the activity of lactate dehydrogenase and lactate enzyme in lined seahorse larvae significantly decreased as the transportation oxygen concentration decreased.（5）In terms of antioxidant enzymes,the activity of catalase,malondialdehyde,and superoxide dismutase in lined seahorse larvae significantly decreased,while the activity of total antioxidant capacity significantly increased.（6）In terms of immune enzymes,the activity of alkaline phosphatase in lined seahorse larvae significantly increased,while the activity of acid phosphatase significantly decreased.2.With the increase of transportation density,significant differences（P<0.05）were observed in the water quality of transported water,survival rate and physiological enzyme activity of lined seahorse juveniles.（1）As transportation density increased,the concentrations of NH₄⁺-N and NO₂^--N in the transported water significantly increased,with the highest levels observed in the experimental group with a density of 1500 individuals/L,reaching 6.6mg/L and 0.032mg/L,respectively.（2）When the transportation density reached 1500 individuals/L,the survival rate of lined seahorse juveniles significantly decreased.（3）With regard to digestive enzymes,as density increased,the activity of LPS and trypsin in the bodies of lined seahorse juveniles significantly decreased,while the activity of AMS significantly increased.（4）In terms of respiratory enzymes,the LD concentration in the bodies of lined seahorse juveniles significantly decreased,while LDH significantly increased.（5）With regard to antioxidant enzymes,as density increased,the CAT activity in the bodies of lined seahorse juveniles showed a trend of decreasing first and then increasing,while MDA showed a trend of increasing first and then decreasing.（6）In terms of immune enzymes,the activity of AKP and ACP both decreased significantly with increasing density.3.With the increase of transportation temperature,significant differences（P<0.05）were observed in the water quality of transported water,survival rate,and physiological enzyme activity of lined seahorse juveniles.（1）As transportation temperature increased,the concentration of NH₄⁺-N in the transported water significantly increased,while the concentration of NO₂^--N first increased and then decreased.（2）The survival rate showed a trend of increasing first and then decreasing with the increase of transportation temperature,and the highest survival rate of lined seahorse juveniles was observed at 19°C,reaching 97%.（3）With regard to digestive enzymes,as transportation temperature increased,the activity of trypsin in the bodies of lined seahorse juveniles showed a trend of increasing first and then decreasing,while the activity of AMS and LPS showed a trend of decreasing first and then increasing.（4）In terms of respiratory enzymes,the LD concentration in the bodies of lined seahorse juveniles significantly increased with the increase of transportation temperature,while LDH showed a trend of increasing first and then decreasing.（5）With regard to antioxidant enzymes,as transportation temperature increased,the SOD and CAT activities in the bodies of lined seahorse juveniles significantly decreased,while the T-AOC activity significantly increased,the activity of MDA decreased first and then increased.（6）In terms of immune enzymes,with the increase of transport temperature,the activity of ACP in juvenile lined seahorse first increased and then decreased,and the activity of AKP first decreased,then increased and then decreased.Through this experiment,we have identified the optimal levels of dissolved oxygen,density,and temperature for the short-term transport of juvenile lined seahorses.We have also identified potential problems that may occur during transport and provided solutions,providing a feasible reference for improving the survival rate and quality of juvenile lined seahorses during actual transport processes.