The ABCs of Stock Assessments


[ music ] U.S. fisheries management is a complex job that relies on sound science. We manage about 450 stocks nationwide, including 230 of the most valuable fish stocks. A big challenge to studying these stocks is that fish are mostly invisible to us and the ecosystems in which they live are always changing. Let’s take a closer look at the science behind managing one of those stocks— the Pacific hake fishery. Also known as Pacific whiting, it’s one of the top five fisheries in the United States by weight and one that was worth $52 million in 2011. The hake fish population has natural and unpredictable ups and downs. We want to take as many hake from the ocean as possible but still leave enough behind to sustain the populations year after year. That’s where fisheries science comes in. NOAA fisheries scientists take a research ship out to sea to collect data on Pacific hake. They use state-of-the-art acoustic technology to find the fish stock and take samples with a net. The data they collect is called the “ABC’s of stock assessment,” which stands for abundance, biology, and catch. Fishery scientists estimate the abundance, or amount, of hake in the ocean and collect biological data to determine things like age and growth rates. Meanwhile, fishermen provide catch data by reporting the amount of fish caught while fishing. All that data is then fed into statistical models that range from simple to complex based on the available data for a given stock. The model results in a stock assessment that we can use to determine a sustainable level of fishing. The data will never be perfectly clear. During a hake population “boom” year, the fish are too small for surveys to count precisely, making it difficult to forecast how many hake will be there in the future. Other years, creatures like squid make an unexpected move into hake territory and obscure results. Issues like these can lead to uncertainty in stock assessment data, which impacts how scientists interpret the data and how managers decide on annual catch limits for the stock. In 2009, the hake survey resulted in a high estimate. In 2011, the hake survey had a low estimate. It was uncertain which estimate was most accurate, but the low 2011 survey suggested that managers should lower annual catch limits in 2012. Since vessel surveys are expensive, we’d have to wait two years before more data were available to inform the status of the hake stock again. Not wanting to wait, the fishing industry approached NOAA with an idea— combine another hake survey with the 2012 scheduled sardine survey. Though the two species live in very different environments and require different types of fishing gear, scientists and industry worked together to carefully plan and execute the sardine-hake combined survey. While scientists were working aboard the stealthy Bell M. Shimada, using sonar to find both species and trawling for sardines, a second ship—the Forum Star provided by industry—trawled for hake. The combined sardine-hake survey did help clear up the earlier uncertainty of the survey estimates. However, the number of young fish remains high, and NOAA scientists continue to develop cutting-edge sonar technology to improve estimates of these younger fish before they are harvested by the fishery. The assessment brought good news for the hake fishery. Managers decided to raise the catch target by 45 percent over the year before. The bottom line—fishery stock assessments are the backbone of successful science-based fisheries management. Rich data streams, strong partnerships, and advanced technology combine combine to produce world-class science. The U.S. approach for managing fisheries sustainably has become an international model for addressing the challenges facing global ocean fisheries today. Thanks to this process, the fishing industry, coastal communities, and our economy can benefit from profitable and sustainable U.S. fisheries. [ music fades out ]

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