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Quantitative Lab: Predator-Prey Relationships
Quantitative Lab: Predator-Prey Relationships

Pinpointing How Forage Fish Availability Affects Seabirds

BRI is collaborating with scientists at NOAA, USGS, and Memorial University of Canada to investigate the importance of predator-prey relationships in the marine environment. Marine ecosystems are complex and dynamic—changes in water temperature, currents, and other factors can alter the distributions of marine fish and wildlife on multiple spatial and temporal scales. As the United States begins to develop its coastal waters to increase energy production with a focus on offshore wind energy development, the patterns and processes that affect distributions of wildlife could be impacted and result in changing food webs. More information is needed on the strengthen our understanding of trophic interactions in our oceans so we can better understand human influence on the marine environment.

BRI Lead Investigators: Evan Adams, Julia Gulka, Chandra Goetsch, Andrew Gilbert, Iain StenhouseKate Williams

New Technology for Tracking Forage Fish Shoals

New Technology for Tracking Forage Fish Shoals

Aircraft have been used for surveys of marine ecosystems for a long time, but recently human observers are increasingly being replaced by digital cameras. These digital aerial survey methods are safer because they can fly higher, and also can detect some animals more often, such as turtles and subsurface fish shoals. Fish shoals—large aggregations of forage fish at the water’s surface—can be detected frequently using these surveys, and represent a taxonomic group for which we previously lacked information. This has provided us with an opportunity to describe distributions of forage fish in ways that hadn’t been done before.

But there is a problem, we can’t identify the species of fish in these shoals because the individual fish are too small. This is where the work of Dr. Kevin Friedland, our collaborator from NOAA, comes into play. Dr. Friedland has been describing the distributions of forage fish using bottom trawl surveys that directly sample the fish, providing species-level across the Atlantic Outer Continental Shelf. However, these surveys don’t happen very often and don’t capture changes within seasons, something that is needed to understand their availability to marine predators like seabirds. By combining these surveys together, we hope to achieve a new understanding of the dynamics of forage fish distributions on the mid-Atlantic and New England Continental Shelves.

Scales of Trophic Interactions

Scales of Trophic Interactions

Once we better understand where forage fish shoals are and why they occur, next we want to understand how they affect higher trophic level species, like seabirds, that rely on these fish for food. While many species, including marine mammals like whales, birds, and large fish rely on forage fish for sustenance, we are focusing on seabirds in this study due to prevalence of data on the distribution of these species and movement of individuals, allowing us to examine these trophic interactions at multiple scales. This work builds off of Dr. Holly Goyert’s research, another project collaborator at NOAA, in linking seabird density to marine community composition. If forage fish are an important resource to a single seabird, the individual will feed in areas where there are more forage fish. If enough individuals do this, we would expect the distribution of the entire population to be linked to forage fish distributions as well. In turn, if these forage fish are so important to the population, then decades-long changes in fish populations could lead to changes in predator populations.

Climate change has been affecting ocean temperatures and shifting distributions of forage fish, just as offshore wind development is being introduced into this system in the eastern United States. Offshore structures can create habitat for fish, which could benefit particular species, but they also can attract new species that weren’t there before and possibly changing food web dynamics. The Outer Continental Shelf, including the mid-Atlantic and New England Continental Shelves, is an ecosystem in flux and we don’t yet know enough about trophic relationships to know how it will change in the coming years as climate change continues to alter marine systems and offshore wind development occurs at increasingly large scales. By understanding the mechanisms and the scale of trophic relationships in this ecosystem, we can begin to understand how different kinds of change will ripple through the food web.

Project Goals

Project Goals

The project team is trying to understand the linkages between forage fish and their marine predators. Understanding these linkages is challenging in marine ecosystems as these systems are extremely dynamic and it can often be difficult to track prey and predators simultaneously. By using digital aerial survey data to better understand changes in forage fish distributions over space and time, we aim to better quantify how prey availability influences predator behavior, distributions and abundance, and long-term trends. Project components include:

  • Compiling digital aerial survey data of forage fish shoals in the Mid-Atlantic and New York Bight to understand the oceanographic factors that lead to forage fish shoals
  • Using satellite telemetry data to describe the movements of Northern Gannets, Red-throated Loons, and Long-tailed Ducks and determine how forage fish availability influences movement behavior
  • Combining aerial survey data for forage fish and seabirds to determine how shifts in forage fish distributions contribute to predator distributions
  • Quantifying decadal trends in forage fish distribution and predator distributions to determine how climate and other habitat changes have affected long-term trophic relationships
Project Funding and Timeline

Project Funding and Timeline

Funding to for this project came from the New York State Energy Research and Development Authority (NYSERDA). The project was initiated in the fall of 2019 and is expected to be completed in early 2023.
 
Photo Credits: Header image: Northern Gannet with a satellite transmitter © Jonathan Fiely/BRI; Aerial survey image of a forage fish shoal © HiDEF Aerial Surveys/BRI; Northern Gannets diving © wildestanimal-Shutterstock; Red Throated Loon with a satellite transmitter © Jonathan Fiely/BRI;
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