Effects of Salinity and Temperature on Embryonic Development of the Petrale Sole (Eopsetta jordani)

Abstract

Newly fertilized eggs were incubated at 13 combinations of levels of salinity and temperature between 20 and 35‰, and 4.1 and 8.5 C. Average egg density throughout development was 1.0252, and the incubation period ranged from 6.2 to 13.5 days. Larval length at mean hatching time averaged 2.84 mm for all trials. External features of the larvae are described. The percentages of eggs hatching (total hatch) and producing viable larvae (viable hatch) are examined with respect to salinities and temperatures of incubation. Calculated optima were: total hatch 29.47‰ S, 6.65 C; viable hatch 27.93‰ S, 7.00 C. At 6.3, 7.2, and 8.1 C, larvae grew to 5.5–5.7 mm total length prior to exhaustion of yolk 246–393 hr after hatching. It was concluded that greatest numbers of viable larvae of largest size at yolk exhaustion would occur from incubation at 27.5–29.5‰ S and 6–7 C.Laboratory results are related to available hydrographic and meteorological data for a spawning area off the west coast of Vancouver Island. Estimates are given of direction, depth, and duration of drift of the pelagic stages until exhaustion of the yolk. Environmental variability in the spawning period is related to existing measures of year-class strength. Effect of temperature on egg development is related to the range of the species in terms of estimated temperatures available at spawning depths.