Sardine Population Remains Low, New Draft Stock Assessment Finds

The sardine population off the West Coast remains depressed despite a closure of the sardine fishery over the last four years, according to a new draft stock assessment that NOAA Fisheries delivered to the Pacific Fishery Management Council (PFMC) this week.

Stock assessments are conducted each year to help determine what the annual fishing levels will be for the upcoming fishing season. The low numbers this year open the possibility that sardines could be determined to be overfished, depending on a series of reviews and consideration by PFMC and NOAA Fisheries. An overfished determination would trigger a process under the Magnuson-Stevens Fishery Conservation and Management Act that calls for the PFMC to develop a rebuilding plan for the stock.

A trend of declining stock biomass has been observed in the sardine assessed off the West Coast, plateauing at recent low levels since 2014, and projected to an estimate of 27,547 metric tons in July 2019. The numbers of young fish added to the population from 2011 to 2017, known as recruitment, have been among the lowest in recent history, the draft stock assessment reports. 

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

If the population biomass falls below a precautionary level of 150,000 metric tons, three times greater than when the stock could be considered overfished, then directed fishing for Pacific sardines is closed. This occurred in 2014 and the directed fishery for sardines has since remained closed. This threshold aims to preserve enough sardines to jump-start a new cycle of population growth when ocean conditions become more favorable.

NOAA Fisheries scientists assess the sardine population 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 extended from San Diego, California, to the northern tip of Vancouver Island, Canada.
 
Low fish numbers make the surveys more challenging because the scarcer fish are, the tougher they are to detect and measure, said Kevin Hill, a SWFSC fisheries biologist who compiled the assessment.

The draft assessment goes first to the PFMC’s Science and Statistical Committee’s (SSC) Coastal Pelagic Species Subcommittee, and then on consideration by the full SSC and then the full Council at the next public meeting scheduled for April 2019. 

Read more about Pacific sardine: 
Assessment of the Pacific sardine resource in 2019 for U.S. Management in 2019-2020. Draft document prepared for SSC CPS Subcommittee review The previous link is a link to Non-Federal government web site. Click to review NOAA Fisheries Disclaimer
Distribution, biomass, and demography of coastal pelagic fishers in the California Current ecosystem during summer 2017 based on acoustic-trawl sampling. NOAA-TM-NMFS-SWFSC-610.
Pacific Fishery Management Council Coastal Pelagic Species The previous link is a link to Non-Federal government web site. Click to review NOAA Fisheries Disclaimer 
California Cooperative Oceanic Fisheries Investigations (CalCOFI) 

Links to past sardine stories:
New methods further discern extreme fluctuations in forage fish populations (2017)
Sardine numbers remain low, 2016 fishing remains closed (April 2016)
Sardine assessment shows cyclic decline in population (April 2015)

For more information, please contact: Michael.Milstein@noaa.gov or Jim.Milbury@Noaa.gov (West Coast Regional Office Public Affairs), Dale.Sweetnam@noaa.gov (Southwest Fisheries Science Center) and Joshua.Lindsay@noaa.gov (West Coast Regional Office)

Q and A

Q: How does SWFSC estimate the biomass of sardine? 
A: The Acoustic Trawl Method (ATM) is used by NOAA's Southwest Fisheries Science Center (SWFSC) to survey the distributions and abundances of sardine and other coastal pelagic species (CPS) and their oceanographic environments. The 2018 summer survey was conducted onboard the NOAA Fisheries Survey Vessel (FSV) Reuben Lasker, one of the world’s most technologically advanced fisheries survey vessels. The survey combines information collected with a suite of state-of-the-art echosounders, trawl-net catches of juvenile and adult CPS, remote and real-time oceanographic measurements, and continuous sampling of fish eggs. Acoustic data were collected during the day to allow sampling of fish schools aggregated throughout the surface mixed layer. Trawling was conducted during the night to sample fish dispersed near the surface. The summer 2018 survey occurred over 80 days at sea (26 June through 23 September 2018), and transects spanned the west coast of the U.S. and Canada, from the northern end of Vancouver Island to San Diego. The survey totaled 5,122 nmi of 106 daytime east-west acoustic transects and 167 night-time surface trawls. 

Q: How have we managed the sardine fishery given that biomass has been low? 
A: As a precautionary measure, the primary directed fishery for sardine was closed in April 2015, when the stock fell below the precautionary cutoff level of 150,000 mt and above  the 50,000 mt overfished level, and it has remained closed since then.. The primary directed fishery will again be closed in 2019-2020.

Q: The draft assessment numbers suggest that the stock is overfished, what happens next? 
A: The draft stock assessment indicates that the northern subpopulation of Pacific sardine is now below the 50,000 mt minimum stock size threshold for an overfished stock as defined in PFMC’s Coastal Pelagic Species Fisheries Management Plan. After the draft stock assessment is reviewed by the PFMC, then NOAA Fisheries will initiate a process to determine whether to formally declare the stock overfished. An overfished sardine population is one with a stock biomass for sardine ages one and older on July 1 of 50,000 mt or less. If the stock is determined to be overfished, NOAA Fisheries will notify the PFMC, who will have two years to develop a rebuilding plan. 

Q: Is the Pacific sardine stock experiencing overfishing? 
A: No.  Under the PFMC’s Coastal Pelagic Species Plan, overfishing occurs if catch exceeds the overfishing limit (OFL). The OFL was 11,324 mt for the 2018-2019 fishing year and the most recent catch statistics are preliminary and incomplete at 1,507 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 population 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: Why are there two different acoustic-trawl method sardine biomass estimates for 2017 mentioned in the 2019 draft stock assessment? 
A: During the course of preparing a NOAA Technical Memorandum regarding the 2017 survey the scientists discovered an error in the depth range used for calculation of the integrated coastal pelagic species (CPS) backscatter from the echosounders. The acoustic-trawl method estimates Pacific sardine biomass from putative coastal pelagic fishes integrated in the upper water mixed layer, typically 10 - 70 m in the spring and 10 - 40 m in the summer. It was later discovered that in the 2017 analysis, the vertical integration utilized to calculate the original estimate, was occurring from 10 - 250 m, which included backscatter from non-CPS species with swim bladders, such as rockfishes and hake. After replacing the acoustic original backscatter data those from only the vertical region where CPS reside, the estimate of Pacific Sardine biomass during summer 2017 is revised here to 24,349 t (CV = 37%). Using the same analysis protocol, the summer 2018 sardine biomass is 35,501 t (CV = 73%).