Tangled up in blue: The role of fish larvae in the complex food webs of the oceanic plankton


***Monday June 11, 2012
Redfield Auditorium - 12:00 Noon
Dr. Joel Llopiz
Postdoctoral Scholar
Biology Department
Woods Hole Oceanographic Institution

For nearly one hundred years, fisheries ecologists have recognized that the population sizes of marine fishes are determined, in large part, by survival rates during the larval stage. Thus, the feeding, growth, and mortality of millimeter-scale planktonic fish larvae are inextricably linked to the many fisheries-dependent components of local, regional, and national economies. Still, the ecologies of fish larvae in the tropics and subtropics have been substantially understudied. In light of this gap, recent efforts in the Straits of Florida sought to shed light on the factors that affect larval fish survival, with particular emphasis on the feeding dynamics of the high diversity of fish larvae that inhabit these waters year-round. Studies showed that many taxa have remarkably narrow diets and exhibit highly selective feeding behaviors influenced by prey type rather than just prey size. Such findings allowed us to address questions as to how larval behavior can shape the spatial and temporal distribution of the dominant trophic pathways from zooplankton to the entire larval fish community. This work also highlighted a critical link between fish larvae and the microbial food web by way of appendicularians, which were found to be one of the most important prey types in these oligotrophic waters. Understanding the relative contribution of the microbial food web to larval fish survival in low vs. high latitudes is one of the major objectives driving my current research, as a recent literature synthesis I conducted on larval fish feeding identified clear distinctions among latitudinal regions in prey types consumed as well as prey selectivity and feeding success. This and other future empirical work that takes a more holistic approach to plankton ecology should greatly advance our knowledge of the functioning of the ocean’s planktonic ecosystems and the factors that may threaten them in a rapidly changing world.