EGG WEIGHT, FECUNDITY, AND GONAD WEIGHT VARIABILITY AMONG NORTHWEST ATLANTIC HERRING (CLUPEA-HARENGUS) POPULATIONS

Egg weight varies among northwest Atlantic herring (Clupea harengus) populations that spawn in different seasons (n = 12), but the range in weights is less than half of that known for northeast Atlantic populations. Egg weights were similar for both spring (May-June)- and autumn (August-October)-spawning herring (1.06 X) and most dissimilar between spring- and summer (July)-spawning herring (1.21 X). Mean population egg weights were not correlated with temperature either at spawning or for the last 2 mo of the egg development period. The product of egg weight and fecundity (standardized to length) differed between spring- and autumn-spawning herring of the southern Gulf of St. Lawrence. Spring-spawners, particularly smaller fish (less-than-or-equal-to 320 mm), have lower ripe ovary weights than do autumn-spawning herring. Differences between spawning seasons in the relative allocation of storage energy to gonad and metabolism, a process mediated by the duration of the gonad maturation period, are the likely basis for the observed patterns.