UBC Theses and Dissertations
Egg size variation in Pacific herring, Clupea harengus pallasi (Valenciennes), and its effects on larval growth and survival Kingston, Gary
This thesis investigated variation in egg size with size of the female parent in Pacific herring, Clupea harengus pallasi (Valenciennes), and the effect of this variation on subsequent larval growth and survival. Egg weight was found to increase markedly with length or weight of the female; larger females had mean egg weights up to 50% greater than those observed in the smaller females. Differences in egg size had no effect on fertilization rate, incubation time, or hatching success, contrary to some of the other findings in the literature. Total weight at hatch, that is, the weight of the larvae and yolk combined, was highly correlated with original egg weight. Larvae from larger eggs generally had more yolk at hatch, grew more quickly on the yolk reserves, and took longer to reach complete yolk absorption. The net result was that small differences in size at hatch were amplified and larvae from larger eggs were substantially longer and heavier at yolk absorption than larvae of the same age from smaller eggs. Under starvation conditions, larvae from larger eggs survived 4 to 5 days longer than larvae from smaller eggs at 9.1 °C. The magnitude of this difference was temperature dependent. When fed an Artemia diet larvae from smaller eggs and larvae from larger eggs had similar growth rates regardless of when feeding was initiated. Trends in survival with egg size were not significant except when feeding was initiated early. In this case, survival declined significantly as egg size increased. Implications of these results in terms of fisheries management are discussed.
Item Citations and Data