Fish were sampled using one of two techniques: the first method involved sampling fish live in the
sling, using a series of visible targets along the ventral surface of the
fish, where opercle bones meet, to insert a needle into the bulbus
arteriosis within 60 s of immobilization in the sling. Fish sampled live
in the sling were then either released back into the tank, without impact,
to be used for future experiments, or were euthanized for additional
cardiac and other sampling studies.