Disparity between planktonic fish egg and larval communities as indicated by DNA barcoding

A genetic identification method (DNA barcoding) was used to compare the community compositions of planktonic fish eggs and larvae within a coastal embayment, testing the hypothesis that the composition of the planktonic larval fish community proportionately reflects the composition of the planktonic fish egg community (excluding species with non-planktonic eggs). By genetically identifying 843 individual eggs, we preserved the quantitative aspects of traditional community analysis. The studied embayment has restricted hydrodynamic connectivity to other coastal waters. A circulation model containing simulated particles estimated average egg movement of approximately 1 km between times of spawning and sample collection, indicating locally spawned eggs were likely to be retained within the survey area. Thirteen of 14 collected egg taxa (88% of egg specimens) could be genetically identified to species level, with the 14th taxon identified to genus level. This novel approach revealed a high degree of spatial heterogeneity in fish egg compositions within the embayment. Species that dominated the egg community (Eugerres plumieri, Cynoscion nebulosus, Centropomus undecimalis, and Prionotus spp.) were not particularly abundant amongst the 276 larvae identified, and the most abundant larval species (Achirus lineatus and Cynoscion arenarius) only comprised a minor proportion of the identified eggs. Overall, there was no correlation between the percent compositions of the egg and larval communities (r=-0.07, n=15, p=0.81). The clear disparities observed between the species compositions of the egg and larvae highlight the need for directly identifying eggs when studying habitat connectivity or performing stock assessment with egg production model-based methods.