All the fish were submitted to the protocol below and results
were distinguished and organized according to individual PIT-tag
number. Prior to environmental challenge tests, fish from both
strains were brought together in the experimental arena and left
undisturbed during 24 h.This arena was identical to the rearing
tanks with regard to location, size and water supply.Following
recovery from the tests (4h) fish werere turned to thei roriginal
rearing tank.