After euthanasia (see Ethical Note)

After euthanasia (see Ethical Note), the fish were weighed (to
the nearest 0.1 g), measured (standard length to the nearest 1 mm)
and decapitated. Fish were immediately frozen at 80 C. At the
time of histology the tail and epaxial musculature were removed
and transverse serial sections were cut at 7e10 mm, stained with
haematoxylin-eosin Y and examined under a light microscope. We
scored the presence or absence of ovarian or testicular tissue.
Hermaphrodite fish were not found.