Net ion fluxes and ammonia excretion during transport of Rhamdia quelen juveniles

Fluxo de íons e excreção de amônia durante o transporte juvenis de Rhamdia quelen

The objective of this study was to verify net ion fluxes and ammonia excretion in silver catfish transported in plastic bags at three different loading densities: 221, 286 and 365g L^-1 for 5h. A water sample was collected at the beginning and at the end of the transport for analysis of water parameters. There was a significant positive relationship between net ion effluxes and negative relationship between ammonia excretion and loading density, demonstrated by the following equations: Na⁺: y-24.5-0.27x, r²=0.99, Cl^-: y=40.2-0.61x, r²=0.98, K⁺: y=8.0-27.6x, r²=0.94; ammonia excretion: y=-11.43+0.017x, r²=0.95, where y: net ion flux (mmol kg^-1 h^-1) or ammonia excretion (mg kg^-1 h^-1) and x: loading density (g). Therefore, the increase of loading density increases net ion loss, but reduces ammonia excretion during the transport of silver catfish, indicating the possibility of ammonia accumulation

fish transport; ionoregulation; load density