The integral temperature for the first zoeal molt of the tanner carb, Chionoecetes opilio, differs insignificantly between two cases, where, the larvae were transferred from hatching sea-water (specific gravity, 1.025) to rearing sea-water (sp. gr., 1.020-1.030) either directly or gradually. In rearing water with sp. gr. lower than 1.015, the direct transfer resulted in slightly longer time for the molt than did the gradual transfer. Survival rate of the first zoea stage was almost the same in both cases within a sp. gr. range of 1.015-1.030.
Minimum time for molting was obtained at a sp. gr. range of 1.020-1.022 in the first and second zoea stages, and at a range of 1.020-1.024 in the megalopas. Thus, sp. gr. range for the most successful molting was considerably lower as compared with that of the water off Wakasa Bay.
Over 70% of tested individuals in the first zoea stage were able to survive in a sp. gr. range of 1.022-1.027 and the range for similar survival in the second zoea stage was 1.019-1.026. Most of the first stage zoea reared at a sp.gr. of 1.012 failed to molt completely, and those which succeeded died within a few days.