Predatory Impacts of Large Medusae on Ichthyoplankton in the Northern California Current (2016-18)

Kelly Sutherland
Oregon Institute of Marine Biology
University of Oregon
5289 University of Oregon
Eugene, OR 97403
Phone: 541-346-8783

Co-PI: Richard Brodeur, Northwest Fisheries Science Center

Jellyfish are key predators in coastal marine ecosystems, particularly during seasonal blooms. In some ecosystems, jellyfish are increasing in number, frequency and magnitude, and can take on a dominant role in structuring planktonic communities through cascading effects. Jellyfish are a key component of food webs but are typically not included in food web models due to uncertainties in the predator-prey relationships. The dearth of studies on jellyfish relates to the difficulty of field sampling; due to their fragile nature, jellyfish require specialized sampling and handling techniques.

Quantitative measurements of the feeding patterns of jellyfish in the Northern California Current are critical for understanding impacts on fish production and, more broadly, will help better understand trophic relationships and construct more accurate ecosystem models. Overlap in space and time between the jellyfish, C. fuscescens, and dominant forage fish species, such as Pacific herring, northern anchovy and Pacific sardine, is particularly high, and these species share a similar zooplankton diet. Likely due to direct competition for prey resources, such as icthyoplankton, there is a negative relationship between C. fuscescens density and forage fish density. As a result, ecosystem modeling predicts that increasing C. fuscescens abundance should lead to a decrease of important forage fishes as well as higher trophic groups in the Northern California Current. Jellyfish also directly impact fishing activities by clogging or entanglement with gear, leading to lost revenues. Further characterization of jellyfish density, distribution and seasonal timing will also be useful for researchers and managers seeking to understand habitat use of a top jellyfish predator — endangered leatherback sea turtles.

Jellyfish and fish overlap in the Northern California Current — with resultant impacts on food webs as well as economic losses for fisheries — demonstrating a need for focused studies on jellyfish feeding ecology, particularly of C. fuscescens. To address this gap, Dr. Sutherland and her research team propose to characterize distributions of large medusae and their prey off the Oregon coast. They will address this research goal over two sampling years through a combination of net sampling, diet studies, and field video surveys via partnerships with local fishermen. They plan to communicate information about jellyfish ecology and their impacts on marine resources to managers, marine science educators and the public through direct communication, two exhibits, and a laminated ID guide.

Strategic Plan Focus Areas: Healthy Coastal Ecosystems,Sustainable Fisheries and Aquaculture

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