Pacific Sardine Assessment

Sardine Ray Troll

Pacific Sardine - Image by Ray Troll


Pacific Sardine Stock Remains Low, 2020 Stock Assessment Finds

The Pacific sardine stock off the West Coast remains at low biomass, according to a new assessment that NOAA Fisheries delivered to the Pacific Fishery Management Council on (the Council) 6 April 2020. NOAA Fisheries scientists at the Southwest Fisheries Science Center conduct assessments of the Pacific sardine stock annually to understand/identify the status of this stock and to advise fishery management for the upcoming fishing season. Assessment and management apply specifically to the northern subpopulation of Pacific sardine. 


The stock biomass was projected to be 28,276 metric tons for July 2020 in the new assessment, a slight increase from the 27,547 metric tons that were estimated for July 2019 in the 2019 assessment. The numbers of young fish added to the stock from 2011 to 2019, known as recruitment, have been among the lowest in recent history. 


Stock assessment improvements

The new assessment included improvements in how abundance is estimated through informative collaborations with industry. This builds on the much larger NOAA Fisheries effort to annually measure sardine abundance off the West Coast from British Columbia in Canada down to the US-Mexico border from large NOAA research vessels using acoustic echosounders and trawl sampling.  Since NOAA’s large research vessels cannot be positioned very close to shore, two new and coordinated efforts to measure nearshore abundance were completed and those results were included in this newest assessment. First, In 2017 and 2019, nearshore sardine abundance was measured in collaboration with the sardine industry by installing acoustic echosounders on industry vessels paired with purse-seine sampling off Oregon and Washington. Second, in 2018 and 2019 unmanned surface vehicles were used to deploy acoustic echosounders off portions of the California coast that were not covered by industry vessels. 


In addition, to account for the very narrow band of nearshore waters closest to the surf zone not covered by the acoustic echosounder measurements listed above, aerial survey estimates of sardine biomass from the California Department of Fish and Wildlife were used to scale up the abundance estimates for 2015-2019. 


Conducting the Pacific sardine stock assessment 

NOAA Fisheries scientists assess the Pacific sardine stock and oceanographic environment off the West Coast annually. Conducted on one of the most technologically advanced fisheries vessels in the world, the most recent survey used acoustic echosounders and trawl sampling, and extended from the northern tip of Vancouver Island, Canada to the US-Mexico border. In addition, due to the success of recent collaborations with industry, NOAA Fisheries plans to continue these partnerships, and current plans are for the upcoming summer 2020 survey efforts to make strides in further extending nearshore coverage with industry help.


This 2020 stock assessment is considered to be the best scientific information available, according to a rigorous set of rules established by the Magnuson Stevens Fishery Management and Conservation Act. Scientists from the Center of Independent Experts as well as the Council’s Scientific and Statistical Committee reviewed the assessment before the Council adopted it for use in management on 6 April 2020. More information about the Council’s management decisions can be found on the Council's website.


Sardine status and trends

Sardines are known around the world for their wide-ranging “boom and bust” population cycles of high abundance and low abundance, as is famously depicted in John Steinbeck’s “Cannery Row.” Periods of few young fish joining the stock can lead to longer periods of low population abundance, even in the absence of fishing.


The stock was declared “overfished” in 2019 when the biomass fell below the overfished threshold of 50,000 metric tons. This was despite the closure of the U.S. Pacific sardine fishery since 2014 when the stock biomass fell below a precautionary threshold of 150,000 metric tons. The higher threshold aims to preserve enough sardines to jump-start a new cycle of population growth when ocean conditions become more favorable.

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Q: Why is estimated fishing mortality so high in recent years?

A: In this assessment, the Ensenada landings were high in 2018 at about 11,000 mt and the landings for 2019 were assumed to be the same. These landings were separated between northern and southern subpopulations of sardine based on temperature-dependent habitat modeling. Because the stock size remains low, these comparatively high landings result in high estimated fishing mortalities. 


Q: Is the Pacific sardine stock experiencing overfishing? 

A: No. Whether the Pacific sardine stock is experiencing overfishing is evaluated using the definition from the Council’s Coastal Pelagic Species Plan, which specifies that overfishing occurs if catch exceeds the overfishing limit (OFL). The OFL was 5,816 mt for the 2019-2020 fishing year and the most recent catch statistics are preliminary and incomplete at 139 mt (U.S. total landings). Annual catch has never exceeded the overfishing limit (OFL) and overfishing has not occurred. In addition, the directed fishery has been closed since April 2015. 


Q: Why is the Pacific sardine stock low?

A: Sardines and other west coast forage fish populations have experienced dramatic fluctuations in abundance (see "Collapse and recovery of forage fish populations prior to commercial exploitation" SWFSC 2017) driven primarily by recruitment, a process that encompasses both reproductive output by adults and the subsequent survival of eggs, larvae and juveniles. Recruitment is affected by a combination of feeding conditions experienced by adult fish, drift of their eggs, availability of suitable food to developing larvae, and predation pressure on all stages. While the effects of climate change on habitat and predation and harvest on adults are difficult to disentangle, the directed fishery for the northern subpopulation has been closed for the last four years so the observed patterns are most likely accounted for by environmental drivers and their effect on recruitment.  

Q: Do the acoustic-trawl survey data and the stock assessment model estimates show the same trends in biomass in recent years

A: Yes, the survey data and assessment model outputs both show similar trends in biomass. The acoustic-trawl survey estimated biomass (“acoustic-trawl survey biomass estimates” column in table below) declined from 2015 to 2019 as did the stock assessment estimates for age 0+ and age 1+ biomass. The overall trend is a decline in estimated biomass, while there is year-to-year variability, due in part to uncertainty in the stock assessment models and the data collection. 


Acoustic-trawl survey biomass estimates (mt) (from table 6 in assessment report)

Stock assessment age 0+ biomass estimates (mt) (from table 15 in assessment report)

Stock assessment age 1+ biomass estimates (mt) (from table 15 in assessment report)






















Q: Why is the biomass south of Point Conception not included in the stock assessment?

A: The NOAA Fisheries acoustic-trawl survey routinely covers the coast south of Point Conception, which has seasonally warmer water temperatures. Only biomass estimates associated with the northern subpopulation from this region are included in the assessment. Exclusion is not based on a geographic cutoff.


Q: Why is the sardine caught off Ensenada counted toward the total catch on the stock in the assessment? 

A: There is a long-standing consensus in the scientific community that sardines off the west coast of North America represent three subpopulations. A northern subpopulation (northern Baja California to Alaska), a southern subpopulation (outer coastal Baja California to southern California), and a Gulf of California subpopulation (see figure). The northern subpopulation is exploited by fisheries off Canada, the U.S., and northern Baja California, and represents the stock included in the Coastal Pelagic Species Fishery Management Plan. And there is now general scientific consensus that catches landed in Ensenada and southern California likely represent a mixture of the southern subpopulation (during warm months) and northern subpopulation (during cool months). Satellite temperature data and habitat models were used to separate catches between the northern and southern subpopulations. Only catches from the northern subpopulation were used in the assessment. 


Q: Are there other survey data that you could use in the assessment? 

A: The NOAA Fisheries acoustic-trawl survey currently being used is designed to capture the range of the northern subpopulation of sardine, and ranges from Canada to the US-Mexico border. It combines acoustic echosounder data with biosampling from trawls in order to measure sardine (and other coastal pelagic fish) biomass. Although there are other surveys that exist off the US West coast, those surveys are not targeted towards coastal pelagic species such as sardine, and they are often of limited and/or patchy spatial or temporal scope compared to the NOAA Fisheries acoustic-trawl survey. Additionally, there is a process for including alternative data sources which requires a formal methodology review and approval prior to inclusion in a stock assessment. 


Q: What improvements are planned for the next assessment? 

A: NOAA Fisheries will continue collaborating with the fishing industry to measure sardine abundance nearshore, and the plan is for the upcoming Summer 2020 acoustic-trawl survey to make strides to extend nearshore coverage over a larger area and even further inshore with acoustic echosounders and purse seining.