Vast Majority of Marine Mammals Caught in CA Set Gillnet Fishery Go Unreported - Oceana USA

Vast Majority of Marine Mammals Caught in CA Set Gillnet Fishery Go Unreported

Oceana analysis shows rampant underreporting of bycatch in set gillnets and demonstrates need to resume independent observer program

Press Release Date: October 2, 2023

Location: Monterey, CA


Jamie Karnik | email: | tel: Jamie Karnik

A new analysis by Oceana found that participants in California’s set gillnet fishery severely underreported how many sea lions and seals were caught and either injured or killed in the fishery over the last 20 years, as required by law. The significant lack of reporting of marine mammal incidents underscores the need for the California Fish and Game Commission’s recent efforts to increase observer coverage of this fishery.

“There is a clear need for state and federal fishery managers to resume observer coverage as soon as possible in the set gillnet fishery. The fact that marine mammal incidents were only reported 6% of the times shows that relying on self-reporting of bycatch simply doesn’t work,” said Caitlynn Birch, Marine Scientist for Oceana. “We need a robust observer program with trained scientists to understand the true impacts on protected and vulnerable species, and of course most importantly better management measures to reduce the overall bycatch in this fishery.”

Federal regulations require all marine mammal takes in the California set gillnet fishery to be reported to the National Marine Fisheries Service (NMFS) within a 48-hour period, and fishermen must maintain an accurate and complete record of catch in logbooks. In the past, NMFS placed observers on set gillnet fishing boats, but they have chosen not to observe the fishery since 2017. Without observers on board, the only source of information on marine mammal bycatch are self-reports from fishermen.

While information is scarce for many years and species, there is sufficient data between 2005 and 2012 for California sea lions and harbor seals to draw significant conclusions. In those eight years fishery participants self-reported 100 incidents of set gillnets catching and either injuring or killing a California sea lion or harbor seal, an average of approximately 12 each year. In contrast, NMFS estimates that over the same period there were actually 1,698 sea lions or harbor seals—approximately 212 per year—caught and harmed by California set gillnets, based on fishery data acquired on trips where an observer was on board.

Oceana obtained that self-reporting data earlier this year via a Freedom of Information Act (FOIA) request and after comparing 20 years of self-reporting with marine mammal bycatch estimates from NMFS concluded that self-reported data is biased, with an extremely low number of reports, and there is a strong need for observer coverage of fisheries that frequently interact with protected species and have high bycatch rates.

Set gillnets are used to catch California halibut and white seabass off Southern California. Previous observer data from NMFS indicates the fishery has one of the highest rates of discarded catch and harm to non-targeted species (known as “bycatch”) of West Coast fisheries. These nets catch many different ocean species, including marine mammals, seabirds, sharks, rays, skates, and other fish that are either unwanted or cannot be kept. The majority of the animals caught in set gillnets are thrown overboard, often dead or dying. Set gillnets are anchored to the seafloor, nearly invisible, and can be as long as the Golden Gate Bridge. Scientific studies have indicated that near 100% observer coverage is necessary to accurately detect and quantify bycatch of rare event species.[1]

After NMFS stopped observing the fishery, self-reporting of marine mammal bycatch has remained low, meaning that underreporting is likely still occurring. Between 2002 and 2012 the number of annual self-reports averaged 13.6 mammals, whereas for the next decade (2012 – 2022), an average of 4.6 mammals were reported each year. 

California voters voted to ban set gillnets in nearshore waters in 1990, resulting in major rebounds in vulnerable fish and marine mammals. But set gillnets are still allowed in federal waters (3-200 miles) off Southern California and beyond one mile around the Channel Islands. The California Fish and Game Commission manages the fishery, and its Marine Resources Committee will be considering new measures, including observer coverage, at its November meeting. 

For more information on Oceana’s campaign to clean up the set gillnet fishery, please visit

[1] Curtis, K. & Carretta, James. (2020). ObsCovgTools: Assessing observer coverage needed to document and estimate rare event bycatch. Fisheries Research. 225. 105493. 10.1016/j.fishres.2020.105493.