Paper: Kaplan, I. C., et al., 2016. Cloudy with a chance of sardines: forecasting sardine distributions using regional climate models. Fisheries Oceanography, v. 25(1): 15–27
Last month, I began work in ocean policy for the US representative of the Monterey district in California. Since then, watching the coastal marine issues that cross my desk, my attention has been drawn to some upsetting trends happening on the US west coast. Commercial ports, that house normally-thriving fisheries you depend on for your seafood, are seeing disastrous closures year after year. And, along the beaches, starving sea lion moms and pups have been washing up in alarming numbers. Why? There are a multitude of reasons, but to single out a key problem: the sardines are disappearing.
Both the fishery closures and the sea lion strandings – especially pups – have made national headlines. The California Governor has formally requested the Secretary of the US Department of Commerce to declare a fisheries disaster along the west coast, which would provide federal relief funding for the fishermen. Sea lions have been turning up too far inland from coastal beaches, alone confused, and searching for food. One little pup even somehow got into a restaurant on a beach in southern California.
As a species, the Pacific sardine is known to have “boom and bust” population cycles: fish numbers rapidly rise and fall over multiple years depending on a variety of environmental conditions. Their population along the west coast has recently seen a “bust” and collapsed due to a number of reasons, including changing ocean conditions and allegations of overfishing.
Pacific sardines are a key forage food for sea lions and many other species, as well as a huge source of income for local and commercial fishermen. Unfortunately, with pupping season well underway and the west coast sardine fishery facing a second year of season closure, sardine stocks are seeing a drastic low. By this summer, sardine populations are forecast to be 33% lower than they were in April 2015, when fishery managers closed the sardine fishery for the season on the grounds that there were too few fish to catch (Figure 1).
The most recent population boom came in 2007, when over 1 million metric tons of fish were estimated to be swimming off the U.S. coast. This was fantastic news for west coast fishermen, especially commercial fishermen who in some years brought in about $20 million annually. However, the population soon became depleted, which led to the managing fishery bodies such as the Pacific Fishery Management Council shutting down the fishery in an attempt to allow the stocks to rebound. Of course, this move drastically hurt employment in coastal towns.
In light of recently drafted projections from NOAA showing this summer’s sardine stock numbers down 97% from 2007, the Pacific Fishery Management Council is expected to elect to keep the fishery closed for another year. This is how the policy side can protect the sardine populations: by making sure there are enough fish left to hopefully replenish the stock. But how do they make these projections, and are they accurate enough?
Improving Fishy Forecasting
The science of ecological forecasting is constantly evolving as a tool for anticipating environmental changes. These forecasts help decision-makers and managers plan for the future, make informed decisions, and take appropriate actions to better manage natural resources. Scientists are now trying to improve the accuracy of these forecasts for species such as sardines.
Sardine spawning habitats and migration patterns have been associated with specific temperature, salinity, phytoplankton concentrations, and nutrients. Using these variables, a group of researchers from west coast fishery research institutions tested short-term modeling forecasting for accuracy in predicting sardine populations.
Dr. Isaac Kaplan and colleagues tested a forecasting tool called J-SCOPE: the Joint Institute for the Study of the Atmosphere and Ocean (JISAO)’s Seasonal Coastal Ocean Prediction of the Ecosystem. J-SCOPE has been developed for the northern west coast to provide projections of physical, chemical, and biological ocean properties on 6- to 9-month time scales. The forecasts are derived using the output from a Climate Forecast System (CFS) model, and a Regional Ocean Modeling System (ROMS). ROMS has been used for other coastal prediction capabilities such as aquaculture and nutrient mapping.
The study tested their forecasting model’s ability to create an accurate forecast of the distribution of Pacific sardines based on comparing the model with real population distributions. They used 2009 as a test year, estimating relationships between forecasted ocean conditions and real sardine population distributions (Figure 2).
Results were encouraging, suggesting that relatively simple models using predictions of temperature and salinity from the J-SCOPE system can be used to forecast the distribution of sardines. This would mean that they have the ability to forecast, with moderate accuracy, sardine distributions 4– 8 months in advance. The method could serve as an early warning signal for fishery managers who make decisions on a monthly or quarterly basis, for instance to adjust harvest or to change areas open to fishing vessels.
For the many fishermen already out of sardine work for this year, and for the scores of sea lion pups who are not getting enough food, this model doesn’t help them much. However, with each improvement to ecological and fishery forecasting, fishery managers may begin to adjust their practices and policies in the future to protect stocks like sardines from becoming depleted in the first place.
Zoe has an M.S. in Oceanography and a B.S. in Geologic Oceanography from URI, with a minor in Writing and Rhetoric. She was recently a Knauss Marine Policy Fellow in the US House of Representatives, and now work at Consortium for Ocean Leadership. When not writing and editing, Zoe enjoys rowing, rock climbing, skiing, and reading.