The diameter and hardness of salmon eggs change once they are
exposed to water. Over the course of about an hour, they absorb water
and harden in a process referred to as “water hardening”. We considered
that this process might have substantial effects on the number of
eggs that might be consumed by a given sculpin and on the minimum
size of sculpin that could consume eggs. Hence, for both sculpin
species, we examined egg consumption of both “fresh” eggs and those
that had been water hardened for at least 1 h in lake water. We measured
the weight of 40 eggs together (± 0.01 g) and the diameter of 10
eggs in a row (± 1 mm) before each trial. The eggs from eight beachspawning
female sockeye were used, with eggs from three females
used in both fresh and water-hardened treatments. We examined the
relationship between egg consumption and sculpin length in a series
of 12 experimental containers. The enclosures, made of fine-mesh
stainless steel screen, had 15-cm-high sides mounted on a 40 × 40 cm
square bottom. The cages were placed on metal stands, with the water
level in each at about 10 cm. The bottom of each cage was covered
with fine gravel upon which the eggs were clearly visible. A 15-cmlong,
6-cm-diameter weighted black ABS pipe was provided as shelter
for the sculpins.