Forage fish and zooplankton food web dynamics
I received a Fulbright Award (you can read more about my application experience in this interview) to study trophic linkages between forage fish and zooplankton with Professor Leonardo Castro) at the University of Concepción in Chile. My research was carried out in Northern Patagonia, where a complex marine ecosystem is at the heart of the region’s great natural beauty and economic importance.
Northern Chilean Patagonia, with its confluence of ocean currents, innumerable channels, fjords, and freshwater sources such as rivers and melting glaciers, has a uniquely dynamic oceanography. The ecosystem experiences significant seasonal variability as nutrient-rich upwelling water in the spring and summer greatly increases productivity compared to the winter.
The zooplankton in Northern Patagonia have three main predators, all of which are ecologically and economically important fish species: the anchoveta (Engraulis ringens), sardine (Strangomera bentincki), and sprat (Sprattus fuengensis). These three open-water schooling fish species are in the functional group called forage fish and form the prey base of a wide array of fish, birds, and marine mammals, thus transferring energy from zooplankton to large predators. They also support numerous important local fisheries.
Over the course of the year with Leonardo Castro’s lab, I researched how these three forage fish species shared their zooplankton prey in three distinct but linked regions of Northern Chilean Patagonia during the spring of 2019. We used ambient zooplankton samples, oceanographic data, and fish stable isotope and gut content analysis to explore this topic. We are also planning a study that incorporates previously collected data, to better understand how these relationships change under different annual conditions.
A greater understanding of these trophic relationships will help managers improve the long-term sustainability of artisanal fisheries as well as provide a baseline assessment of relationships between lower and mid trophic-level species against which future studies of the region can be compared. Characterizing ecosystem mechanisms and species interactions will allow better understanding and prediction of the region’s resilience to the warming climate and changing uses of marine resources.
