Ectonucleotidase and acetylcholinesterase activities in silver catfish (Rhamdia quelen) exposed to different salinities

► Silver catfish were gradually adapted to salinities of 0, 4 or 8 ppt. ► Blood AChE activity decreased significantly at 8 ppt. ► Brain AChE activity decreased significantly with salinity increases. ► There is an enhancement in the ADP hydrolysis in the brain of silver catfish. ► The activities of AChE and NTPDase can act as markers of salinity changes in fish.