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DFG and California Wetfish Industry Fly High to Count Pacific Sardine
Co-author Kirk Lynn and pilots search the sea surface for sardine schools
by Kirk Lynn, Environmental Scientist, and Bill Miller, Environmental Scientist
In an effort to improve Pacific sardine stock assessments, DFG and the California Wetfish Producers Association (CWPA) have combined resources to count schools of sardine in southern California. This collaborative study tests the feasibility of using small aircraft to survey sardine and add to our understanding of the distribution of sardine throughout the Southern California Bight.
"These surveys will help DFG to manage this fishery in a sustainable manner and add to our limited understanding of sardine distribution throughout the Southern California Bight," said Michelle Horeczko, senior environmental scientist on the Coastal Pelagic Species Project. "Data from these surveys may also be used by West Coast scientists as part of a new effort to look at the full range of sardine data from Canada to Mexico."
Pacific sardine are a small schooling fish found in the upper layers of coastal temperate waters ranging from Baja California, Mexico to southeast Alaska. The species is managed by NOAA Fisheries through the Pacific Fishery Management Council, which uses a federal Coastal Pelagic Species Management Plan as a framework to manage Pacific sardine as well as other coastal pelagic species ("pelagic" means the species lives in the upper layers of open ocean waters). In 2011, Pacific sardine was the second largest commercial fishery in the state of California by volume, and sixth largest in value.
The use of small planes to find fish in the ocean is not new. Ever since the first sailor climbed into the crow's nest for a bird's eye view, fishermen have understood the advantage of height when scanning the ocean for fish. Spotter pilots have long been a resource to fishermen in locating commercially valuable fish such as swordfish and sardine.
Recent efforts by the sardine industry in the Pacific Northwest have demonstrated the usefulness of this technique off the coasts of Washington and Oregon, when applied scientifically. Since 2008, a consortium of industry members has successfully run an annual sardine survey using aircraft to photograph sardine schools along systematically spaced transects. Using software, the photographs are enhanced to make sardine schools stand out from the background and the area of each school is measured from the photograph. That area can be related to how many tons of fish are actually in the school to come up with an estimate of total biomass.
The southern California survey conducted jointly by DFG and CWPA builds upon techniques used in the Pacific Northwest. An experienced industry spotter pilot was contracted by CWPA to contribute expertise in identifying sardine schools from the air while flying transects in DFG's Partenavia P.68 survey plane operated by a DFG pilot. A DFG fisheries biologist was onboard to direct the survey and record data. An automated Nikon D-series camera system on loan from CWPA was mounted to the floor of the plane, and digital images of fish schools were collected along with transect data such as flight altitude, GPS location, and pilot observations of sardine schools. On the water, DFG biologists tested techniques to ground truth aerial identifications of fish by dropping a submersible camera on fish schools identified from the air to obtain visual underwater observations.
According to Kirk Lynn, an environmental scientist with the Coastal Pelagic Species Project and aerial survey project lead, "This joint project is an opportunity to use and adapt existing aerial methods to examine the specific patterns of distribution and abundance of sardine here in southern California."
NOAA Fisheries traditionally uses egg counts to estimate sardine abundance. This year, in addition to the egg counts, scientists plan to use a combined effort to look at the full range of sardine from Canada to Mexico using egg counts, hydro-acoustics, and aerial photography.
For more information about sardines and sardine fishery management, visit DFG's Coastal Pelagic Species/Highly Migratory Species website.
Sardine surveys were conducted from DFG's
Partenavia P.68 survey aircraft
View from DFG survey aircraft flying
over Santa Cruz Island