Tracking wildlife is much different — and harder — in water. Beyond the difficulties with visibility, fish are also buffeted by currents in a way that terrestrial animals are not, making it difficult to model their communities and evaluate the ecosystems in which they participate. Now, researchers are leveraging supercomputing power at the San Diego Supercomputer Center (SDSC) to model the currents that transport fish along the California coast.

To accomplish this, the researchers — hailing from the University of California, Los Angeles, and the University of Montpellier in France — leveraged a regional implementation of the APex ECOSystem Model (APECOSM), which models the pelagic food web. They targeted APECOSM at the California Current Ecosystem (CCE) that stretches from Canada to Mexico and coupled the model with an eddy-resolving simulation of ocean currents. Then, they tuned the model to accurately reproduce fishing hauls from fisheries along the CCE.

To run these simulations, the researchers turned to Expanse, SDSC’s Dell-built system that leverages AMD CPUs and weighs in at 2.48 Linpack petaflops, placing 259th on the most recent Top500 list. Time on the Expanse system was allocated to the researchers through the Extreme Science and Engineering Discovery Environment (XSEDE) program.

The simulations showed that the currents in the CCE can carry fish miles away from where they congregate and even trap fish in vortices.

“Our results highlight the importance of currents and swimming fish in structuring the pelagic food web, and suggest that a representation of these processes can help to improve the realism in simulations with marine ecosystem models,” explained Fayçal Kessouri, a senior scientist at the Southern California Coastal Water Research Project, to SDSC/UCSD’s Mahathi Gorantla and Kimberly Mann Bruch. “These circulation features generate environmental variations, or ‘fronts’ at scales of kilometers that influence the suitability of the environment to fish, shaping figurative hills and valleys where species will thrive or that they will avoid.”

There remain a number of major unknowns, including how the currents affect the prevalence of fish and the health of the ecosystems in which they reside — but nevertheless, the research is an important step in understanding and managing fish populations, from the protection of endangered species to climate adaptation measures. Along those lines, the researchers plan to next tinker with the simulations to see how climate changes might affect the abundance of fish in the CCE.

To learn more about this research, read the paper here and read the coverage from Mahathi Gorantla and Kimberly Mann Bruch here.