News & Views
Study identifies optimum parameters for transport of live Peruvian grunt
By Ruby Gonzalez
Pinning down parameters in transport of live Peruvian grunt (A. scapularis) juveniles has removed one of the choke points in furthering research on the new species for aquaculture development in Peru.
Transporting fish has caused mortality at or after seeding because of poor physiological conditions of haul stress. Seawater quality and stocking density have major impacts on survival rate. During transport in polyethylene bags, the survival rate of Peruvian grunt juveniles was higher at low densities and duration, according to the study by Luis A. Espinoza-Ramos et al.
“The transport of live fish for aquaculture is a key issue in the domestication of new species. National level programs were developed in Peru for controlled repopulation of Peruvian grunt (Anisotremus scapularis), reared in extensive systems or ongrown in floating cages, but these were limited by inadequate knowledge of the best transport parameters to ensure survival,” the authors said in, ‘Effect of transportation time and stocking density on seawater quality and survival of Anisotremus scapularis (Perciformes: Haemulidae)’, published in the Journal of World Aquaculture Society.
The researchers evaluated the effects of stocking density and transport time of the animal, and analyzed key parameters such as seawater temperature, dissolved oxygen, pH, ammonia, during transport and effect of these on survival. During the experiment, groups of animals were deposited in 24-litre volume polyethylene bags with eight litres of sterilized seawater. Low-density (LD) bags had 48 animals; medium (MD), 72; and high (HD), 96.
Each density was at eight, 10, and 12 hours of transportation.
The highest survival rate was posted in treatments performed at eight hours — 100 per cent — in MD. No significant variance was noted in survival rates among the densities. LD had 95.83 per cent and HD, 97.92 per cent.
Highest mortality came from the 12 hours with HD at 70.49 per cent; MD, 67.13 per cent; and LD, 61.11 per cent.
Factoring in other variables and parameters that were not measured such as stress, the study recommends transport of LD at eight hours. There is a leeway for up to 10 hours of transport time and 72 animals per bag of stocking.
The highest ammonium concentrations were reported in treatments with HD at 10 and 12 hours, as well as at MD at 12 hours of transport, and the lowest concentration in treatment LD at eight hours of transportation.
The direct proportion between the ammonium concentrations and density, with the degradation of seawater was traced to increase of fish excretion metabolites.
Seawater temperature increased the end of all experimental treatments compared to the initial temperature.