A study of the ecology of developing embryos of the Pacific surf
smelt, Hypomesus pretiosus, was conducted. Embryos were maintained in the
laboratory at 7.6, 12.1, and 17.6°C and the time to specific embryonic stages
determined. Embryos held at 7.6°C developed to stage 24, 18 days after collection;
those held at 12.1°C hatched after 13 days; at 17.6°C hatching occurred 8.5
days after collection. Embryos maintained at 15°C and salinities of 20, 25, and
30%0 averaged 84% survival. There was no significant difference in survival
between the groups (ANOVA, P = 0.53).
Field observations indicated that embryos are spawned in patches in the upper
intertidal zone near the time of high tide. They are attached to gravel substrates
by the zona radiata membrane which ruptures and quickly turns inside out at
the time embryos are fertilized. After several days of development, stage 18 to
22 embryos detach from the original spawning substrates and are washed seaward
and down into the gravel substrate in the intertidal zone. However, there
was no significant difference (ANOVA, P >2: 0.09) in the number of eggs found
at each of 4 depth strata in the upper, middle, and lower intertidal zones
