Comparative morphology, seasonality, and a key to planktonic fish eggs from the Nova Scotian shelf

Abstract

The pelagic fish egg fauna of the Nova Scotian shelf consists of 16 species plus 5 predominantly slope species that occasionally drift onto the shelf. In 9 of these 21 species there were no morphological characters that could be used to identify early, pre-embryonic eggs. In the remainder, chorion structure, egg diameter, or egg versus oil globule diameter scattergrams could be used to completely or partially diagnose species identities. A key to the 21 species of eggs is presented. On the shelf proper pronounced seasonal variation was observed in presence or absence of oil globules with species having oil globules restricted to the period April to October. Seasonal variation was also observed in egg sizes and adult sizes, with species attaining a large body size producing large eggs in colder months, while smaller species producing smaller eggs (usually with an oil globule) spawned in warmer months. These seasonal patterns are not resolved but appear related to buoyancy requirements, metabolic rates, first feeding requirements, and phylogenetic constraints.