Fishery Data, On the Double: NOAA Fisheries and Industry Join Forces on Combined Hake/Sardine Survey
Hake, a.k.a. Pacific whiting, top, and sardine (not drawn to size). This past summer, NOAA Fisheries developed a method for surveying these very different species at the same time.
Scientists aboard NOAA ship Bell M. Shimada fished for sardine at night in areas where their daytime sonar findings indicated the presence of sardine.
The 208-foot NOAA ship Bell M. Shimada is outfitted with an advanced echo sounding sonar system for fish surveys. Although it is riding rough in this photo Shimada is a quiet vessel, meaning it's engineered to run quietly so that it can search for fish without scattering them.
Read about NOAA’s Advanced Survey Technologies Group, a team of scientists who develop new technologies for keep an eye on what’s happening in the ocean.
Learn how NOAA conducts stock assessments: Fish Stock Assessments 101.
November 26, 2012
NOAA Fisheries is responsible for conducting stock assessments of commercially valuable species of fish. But when doing stock assessments, NOAA scientists aren’t just counting fish. They’re using the latest technology to estimate fish abundance now and into the future, and they’re constantly developing new methods to get more accurate results. This past summer, for instance, NOAA Fisheries developed a new procedure for surveying both Pacific hake and sardine at the same time. This combined survey method, which required a shared effort by both NOAA and the fishing industry, may allow for more frequent abundance estimates for both species, and for better-managed, and potentially more productive fisheries.
The need for a combined survey arose from unexpected survey results in 2011. Pacific hake and Pacific sardine are surveyed on alternate years, and last year's hake survey returned numbers lower than expected. Like many species of fish, hake populations tend to fluctuate from year to year, and it was unclear whether the low abundance estimates resulted from natural fluctuations of the fish stocks, or from the scientific uncertainty inherent in fish population estimates.
Hake, also known as Pacific whiting, is the target of one of the top five fisheries in the United States by weight and one that was worth $52 million in 2011. NOAA scientists found the stock to be overfished in 2002, but thanks to sound management since then, the hake stock has been rebuilt. Sardine were the target of a $10 million fishery last year, and they are declining in sync with natural cyclical forces in the Pacific. Considering both the economic value of these species and their historical shifts in abundance, it is important to get the best data possible for both. But good data, and the fish surveys that produce it, are expensive. For this reason, NOAA alternates between hake surveys one year and sardine the next.
According to Rod Moore, Director of the West Coast Seafood Processors Association, the industry wanted to squeeze in an extra hake survey this year to clear up the uncertainty around last year’s results. So they approached NOAA with the idea of piggybacking a hake survey onto this year’s regularly scheduled sardine survey.
“Next thing you know,” Moore said, with understatement typical of the New Yorker he once was, “we’ve got a survey running.”
An Ambitious Plan
In fact, the combined survey required months of careful planning. Acoustic-trawl surveys, as these are called, involve first searching for fish using sonar, then doubling back to trawl for a sample, which is used to verify the sonar findings and to collect other biological data. But because the two species live at different depths and therefore require different types of fishing gear, there is no simple way that a single ship can trawl for both. The solution was to rig NOAA’s acoustic survey ship Bell M. Shimada for surface trawls for sardine and to rig a second ship—this one, Forum Star, provided by the industry— for midwater trawls for hake. The two would travel together, with Shimada using sonar to search for both species during the day, Forum Star tagging along to sample hake, and Shimada then doubling back to catch sardine at night. They would also collect ecosystem data and data on other species of fish and zooplankton throughout.
Working in tandem, the two ships ran transects along the west coast—one east-to-west transect every ten miles—from the south end of Monterey Bay all the way up to Vancouver Island, where they handed off to Fisheries and Oceans Canada. As a result, NOAA has a new method for simultaneously surveying two very different species of fish. And scientists and the fishing industry will not have to wait until 2013 for an update on the status of the hake population.
Sonar echogram showing coastal pelagic species, which may or may not be sardine, relatively
Making It Work On the Water
Doing a combined survey for both hake and sardine is unprecedented because the two species live in very different environments. Hake is a
demersal species that aggregates near the shelf break at about 200 to 400 meters deep. Sardine, on the other hand, is an epi-pelagic species that lives much nearer to the surface. In addition to requiring different types of fishing gear, the different depths also complicate the sonar situation, since sonar can be optimized for only one depth or another.
The 208-foot Bell M. Shimada is a quiet ship, meaning it’s engineered to move stealthily so that it doesn’t scatter fish as it searches for them. In the acoustics lab, you might not even know you were on a boat if not for the slight pivoting of the floor beneath your feet. It was in this quiet environment that sardine experts and hake experts collaborated on a sonar configuration that would allow them both to find what they were
looking for, and then coordinated the trawl sampling by the two ships.
Larry Hufnagle, supervisory physical scientist and the Acoustics Team Lead for NOAA’s Northwest Fisheries Science Center, led the hake half of the survey. He explained the need for a trawl sample. “We get a target strength,” he said, referring to the intensity of the echo that bounces off the formations of fish below, “we get a depth. But until we fish it, or something similar nearby, we don’t know for certain what we’re looking at.” That’s because hake often associate with rockfish, and you have to pull some up to know how much of each you’ve got.
Dave Demer, senior scientist and leader of the Advanced Survey Technologies Group at NOAA’s Southwest Fisheries Science Center,
directed the sardine half of the survey. He had his own confounding elements to deal with. “Echoes from sardine schools can be very similar to those from mackerel schools,” he said. Again, a sample clears things up.
Once the fish were brought onboard, biologists sorted the catch. They also collected other pieces of data that figure into the stock assessment, weighing and measuring the fish, and dissecting them to determine reproductive status and to see what the fish were eating. The survey crew did this every day, in two twelve-hour shifts, for the duration of the 60-day cruise.
Collaboration Pays Off
Later, after the cruise ended, scientists combined the survey data with other sources of data to produce the stock assessments. In the case of sardine, the acoustic-trawl data joined data from aerial surveys run by the industry. In the case of both species, industry-reported landings and data from state monitoring programs were added in. Scientists then fed all of these numbers into statistical models that output the final stock assessments.
Rod Moore, the West Coast Seafood Processors Association Director who helped launch the survey, remembers a time when such collaboration would not have been likely. “When I first came out here from the east coast 18 years ago,” he said, “there was a lot of distrust between the science folks and the industry.” Since then, things have changed. The successful rebuilding of hake stocks since 2002 is a good example of how cooperation between scientists and industry has produced results. And this year’s combined hake and sardine survey is as well. “It was having that strong history of working together that allowed us to get this thing off the ground so quickly,” Moore says.
As of this writing, NOAA scientists are still crunching the hake numbers. The sardine numbers are already out.