In the ocean, everything moves. Waves push around vast swaths of saltwater, tides ebb and flow, and over time tectonic rumblings transform the seafloor. With all that movement, marine life travels as well—making the oceans one of the most dynamic ecosystems on Earth. This constant shuffling can make it hard to predict where a particular marine species might be on any given day. But that is exactly what Elliott Hazen, a fisheries scientist from the National Oceanic & Atmospheric Association (NOAA), is trying to do through new modeling software.
Hazen and a team of other fisheries scientists developed EcoCast in an effort to reduce the unintended bycatch of protected marine species while supporting sustainable fisheries; their results were published last week in Science Advances. EcoCast is already being used to allow fishermen exemptions to fish in certain protected areas in California, and NOAA is working on a smartphone app that will give fishermen this dynamic data in real-time.
The team focused on the California Drift Gillnet (DGN) fishery, which targets broadbill swordfish along the U.S. West Coast. The fishery, which has declined in recent years, only brought in 176 metric tons of swordfish in 2017—down from a historical high of 2,198 metric tons in 1985. DGN fishermen use mesh nets that float vertically in the water to catch the swordfish, but the nets often trap additional species—a phenomenon known as bycatch—including the critically endangered Pacific leatherback sea turtle, blue sharks, and California sea lions.
It’s not just an issue of protecting endangered species, explains Gary Burke, a fisherman in California and a member of the Commercial Fishermen of Santa Barbara. “Fishermen don’t want bycatch. It breaks our gear and it’s expensive. So, we like to avoid it.”
EcoCast takes an array of oceanographic variables into account to generate a fluid map that highlights areas where fishermen are likely to find high concentrations of their target species and not the protected species they don’t want to catch.
In this case study, Hazen used tracking and observer data for the three species that could wind up as bycatch—Pacific leatherback sea turtles, blue sharks, and California sea lions—as well as swordfish themselves to determine what types of conditions they favored. Things like water temperature, water depth, water turbulence, and the amount of Chlorophyll A—a proxy for the amount of food in an area—combined to create spots the particular species is drawn to visit. Knowing exactly where animals travel (and when) can give scientists an idea of why these patterns happen.
By pulling that information into computer models, the researchers can produce maps in EcoCast that use live ocean conditions to predict whether the target species will be present in an area on any given day—like your daily weather forecast, but with more variables. “Previously people looked at management according to a single variable such as temperature,” says Hazen, “but we know that animals interact with their environment at multiple scales and for multiple reasons.” Hazen continued, “Having a suite of different oceanic variables gives a better view of the oceanic landscape that animals are choosing from.”
The use of a dynamic modeling software could be a better way for managers to decide on fishing regulations in a way that protects species and preserves a valuable fishery. It also can help make decisions about where marine protected areas—spaces where fishing is limited or banned—should be located in the face of rapid ocean changes due to climate change.
Currently California DGN fishery regulations designate a Pacific Leatherback Conservation Area closed to fisheries annually from August 15 to November 15 to protect the sea turtles from gillnets. When Hazen and his colleagues applied the EcoCast model to the these areas, however, they found dynamic closures could be much smaller in size—up to 10 times smaller in fact—and would still protect the turtles at the same level.
This dynamism and recognition of a fluid ecosystem is potentially EcoCast’s most promising feature, says Heidi Taylor, a fisheries manager from NOAA who works with the DGN fishery. Taylor says, “This tool is going to be most useful for fishermen and it’s important that fishermen use this tool in order to weigh their options and make an informed business decision about where to cast their nets.” Taylor is hopeful about the possibility of EcoCast aiding the decision-making process that surrounds balancing viable fisheries with preserving ocean habitat.
With a daily update to the map EcoCast could certainly help determine where a gillnet fisher might head on any given trip, and Burke says fishermen are willing to give the newly available, free data a try.
Fine-tuning EcoCast to accurately forecast where populations of various marine species are is a work in progress. As our climate changes and oceans get warmer, animals will modify their usual routes and behavior patterns. EcoCast will need to be updated continuously as new information becomes available. But the fluidity of EcoCast is the beauty of it.
Learn more about the seas with the Smithsonian Ocean Portal.