View in Vital Signs- Thriving Species and Food Web
- Forage Fish
- Indicator
- Biomass of spawning Pacific Herring
- Vital Sign Indicator
- Metric Ton (metric tons)
- /
-
No targets are currently set for this indicator.
-
Phillip Dionne
- Contributing Partners
-
- Last Updated
- 3/13/2024 9:51:23 AM
The biomass of spawning Pacific Herring indicator is the estimated annual tonnage (four-year average) of herring that have reproduced in Puget Sound. Estimates are based on surveys of the density and extent of eggs deposited by herring on marine vegetation. Herring, along with a few other small schooling fish species, play a unique role in the food web: they are an essential source of food for larger fish, seabirds, and marine mammals.
Four-year average spawning biomass estimates for three genetic stock groups and the combined total are shown with dashed and solid lines; dashed lines represent periods of incomplete data; each color corresponds to a different stock group, and black is the combined total of all stocks. The 25-year mean (1986-2010) for each stock is referenced as a baseline and is shown with horizontal dotted lines of corresponding colors.
Herring are a small schooling fish species that plays a critical role in the food web: they are an essential source of food for seabirds, marine mammals, and larger fish, including Pacific salmon. Herring require clean water and natural shorelines, so their continued survival depends on maintaining links between nearshore and open-water habitats.
- In 2023, the 4-year average spawning biomass for the Other Stocks Complex exceeded 14,000 metric tons for the first time in this time series. This high average is the result of high spawning biomass in 2020 and 2023, and about average spawing biomass in 2021 and 2022. The Other Stocks Complex consists of all Puget Sound herring stocks other than Cherry Point and Squaxin Pass. In contrast, the 4-year averages of the genetically distinct Cherry Point and Squaxin Pass stocks remain well below their baselines. Therefore, our conclusion about progress of Pacific Herring stocks in Puget Sound remains “Mixed.”
- We estimate 17,984 metric tons of total herring spawning biomass for the southern Salish Sea in 2023. This is an increase of about 39% from 2022, but is shy of the recent high estimate of 18,559 metric tons in 2020 (click here to download a table of annual biomass estimates).
- No spawning was observed for the Cherry Point herring stock in 2023. This is the first time in the history of these surveys that we did not find evidence of spawning by the Cherry Point herring stock. It is worth noting that our surveys did not extend into Canadian waters in 2023, so spawning may have occured outside our survey area. Surveys will be extended into Canadian waters in 2024.
- Record high spawning estimates were observed in 2023 at the Port Orchard/Port Madison and the Purdy spawning areas leading to the highest estimates of spawning biomass we've observed in both the Central and South Sound regions.
- During the 2023 season we continued to observe shifts in spawning distribution for some stocks and once again observed herring spawning in areas that had not been previously documented.
- Monitoring Program
Washington State Department of Fish and Wildlife, Marine Fish Unit (Forage Fish)
- Data Source
Washington State Department of Fish and Wildlife, Marine Fish Unit (Forage Fish)
The biomass of spawning Pacific Herring indicator is the estimated four-year average tonnage of reproducing herring in greater Puget Sound (also referred to as the southern Salish Sea). Studies have identified two genetically distinct stocks in Puget Sound, Cherry Point and Squaxin Pass. This indicator reports on abundance trends for these stocks independently, and for all other stocks combined as the Other Stocks Complex.
Herring spawning biomass is based on surveys of spawn deposition conducted by the Washington State Department of Fish and Wildlife (WDFW). Surveyors estimate the density and spatial extent of eggs deposited by herring on marine vegetation. Egg coverage is then converted to the estimated biomass of spawning herring, based on assumptions about sex ratios in spawning aggregations, average female fecundity, and the area of the spawning grounds. The indicator reflects the status of reproductive fish (males and females) and not the status of the entire population because younger, immature age classes do not spawn.
WDFW has monitored Pacific Herring annually in Puget Sound since 1973. Estimates began with the Cherry Point stock and have since expanded to include a total of 21 stocks. Surveys of spawning biomass have been consistently attempted for all known Puget Sound herring stocks by WDFW since 1996. The status of each stock is evaluated by the most recent four-year mean spawning biomass. The 25-year mean of each stock (1986-2010, or for as long as we have data if less than 25 years) serves as the baseline reference value and provides perspective on the current status.
- Critical Definitions
Puget Sound herring data are characterized by broad year-to-year fluctuations (Figure 2). This pattern is typical of Pacific Herring and other forage fish populations, and likely reflects natural environmental and demographic variability. In the past twelve years we have observed both our lowest and second highest estimates of total spawning biomass in Puget Sound. During this 12-year period, we recorded the lowest spawning biomass estimates for 13 of the 21 stocks, and recorded the highest spawning biomass estimates for eight stocks. In Puget Sound, the bulk of the biomass of the Other Stocks Complex is contributed by different stocks in different years, further implicating the role of site-specific variability.
An ongoing challenge in assessing and understanding fluctuations in herring stocks is a lack of information about the population dynamics of the stocks. During the 2021 and 2022 spawning seasons, in partnership with the Suquamish Tribe and with funding from the National Estuary Program, we had the opportunity to implement a paired acoustic trawl sampling design to collect herring and estimate herring biomass at several historically documented pre-spawn holding areas (2021: Port Orchard-Port Madison, Quilcene Bay, and Port Gamble; 2022: Port Orchard-Port Madison, Elliott Bay, Holmes Harbor and Port Susan).
Biomass estimates from acoustic trawl methods correlated with estimates derived from egg deposition surveys but were generally lower. This discrepancy can largely be explained by known biases of these methodologies, as well as rapidly shifting spatiotemporal distribution and short residency time of spawning herring in the pre-spawn holding areas. The acoustic trawl methods also provided biometric samples of spawners, which have long been recognized as a shortcoming of the egg deposition surveys for stock management.
Overall, herring biometrics (length, weight, sex, etc.) varied more for the 2021 samples than samples from the 2022 surveys. The Quilcene Bay stock boasted the largest and oldest fish sampled for this project (Figure 3). Additionally, 65% of Quilcene Bay fish sampled were female. The Quilcene Bay herring stock has had one of the largest spawning biomasses in Puget Sound for the better part of the last decade, which is likely the reason this stock was dominated by older fish. The smaller proportion of 2-year-old fish at Quilcene Bay in 2021 compared to 3- and 4-year-old fish could be evidence of weak recruitment from the 2019 spawning season, and would predict a smaller spawner return in 2022, which is what we observed (only 1,688 tonnes estimated from egg deposition surveys in 2022 compared to 3,289 tonnes in 2021). In 2023, Quilcene Bay continued to decline to 1,465 tonnes, but at a slower rate than the previous two seasons' declines. Interestingly, herring sampled from the Port Orchard-Port Madison stocks in 2021 and 2022 were nearly identical in size and weight, and both years were composed primarily (>50%) of 2-year-old herring.
While more males than females were collected in the 2021 sample than the 2022 sample, the proportion of males in the Port Orchard-Port Madison stocks overall was similar (40 to 45%). Given the record spawning biomass observed in 2020, we were hopeful that the high proportion of 2-year-old fish in 2022 was evidence of a good survival of the 2020-year class and that we would observe another good spawning season in 2023. Our optimism was warranted because 2023 was another record year for the Port Orchard-Port Madison stock which we estimated had 7,473 tonnes of spawning biomass.
-
The exact causes of Puget Sound herring stock volatility are unknown but reports of increased spawning biomass in other parts of the NE Pacific in 2020 tell us that favorable ocean conditions led to higher survival rates for herring which spawned in 2020. The offspring of these fish were likely the bulk of the fish observed spawning in 2023 and will hopefully survive to spawn for several more years to come. The reason that some stocks continue to decline is also unknown, but the differences in abundance between spawning areas may be evidence of local factors influencing recruitment or of different migration patterns between stocks leading to differential survival. Alternatively, there may be less fidelity to spawning areas within Puget Sound than expected and shifting distribution between spawning areas from year to year could give the appearance of fluctuations in local abundance while overall abundance remains more stable.
A recent review of threats to Salish Sea herring stocks in the 2018 report: Assessment and Management of Pacific Herring in the Salish Sea: Conserving and Recovering a Culturally Significant and Ecologically Critical Component of the Food Web (see the executive summary), describes many of the threats that experts in the region think are the most likely culprits for decline.
Threats to Pacific Herring populations identified as common across the Salish Sea include:
- Predation by marine mammal populations undergoing population increases (Harbor seals, Harbor porpoises, sea lions, humpback whales)
- Noise from vessel traffic
- Water quality degradation
- Habitat degradation, including loss of submerged vegetation and shoreline hardening
- Cumulative impacts of shoreline development, including noise, ambient light, poor water quality, and habitat degradation
Threats to Pacific Herring populations identified as unique to areas of the Salish Sea
- Contaminants that increase embryo mortality and embryo and larval malformations (Puget Sound)
- Fishing that may cause local extinctions when interacting with populations having certain migration patterns (Strait of Georgia)
An ongoing challenge in assessing and understanding fluctuations in herring stocks is a lack of information about the population dynamics of the stocks, their food web, and their environment. The disparity in spawning abundance among stocks in Puget Sound suggests that not all stocks are exposed to the same stressors equally and highlights the need for more comprehensive monitoring of these factors. Our acoustic trawl surveys during 2021 and 2022 provided samples of herring at a critical point in their life history, but regular sampling is needed to allow us to understand patterns in survival, growth, and recruitment.
REFERENCES
Sandell, T., A Lindquist, P. Dionne and D. Lowry. 2016 Washington State Herring Stock Status Report. Fish Program Technical Report Series FTP 19-07. 84 pp.
Stick, K., A. Lindquist and D. Lowry. 2012 Washington State Herring Stock Status Report. Fish Program Technical Report No. FPA 14-09. State of Washington. 97 pp.
The Salish Sea Pacific Herring Assessment and Management Strategy Team. 2018. Assessment and Management of Pacific Herring in the Salish Sea: Conserving and Recovering a Culturally Significant and Ecologically Critical Component of the Food Web. The SeaDoc Society, Orcas Island, WA. 74 pp.
EXTERNAL LINKS
Washington State Department of Fish and Wildlife, Marine Beach Spawning Fish Ecology
The Puget Sound Partnership believes in the transparency and accessibility of the data used to address puget sound indicators. These data are provided by contributing partners to the Partnership and are made publicly available through the Puget Sound Info site. These data are available on an "as is" basis and the Partnership is not responsible for any errors, omissions, or inaccuracies. Please acknowledge the monitoring program and data source when using these data and obtain permission from the Vital Sign Indicator Reporter to use these data in a publication.
- HerringSpawningBiomassTable_1973-2023
- Uploaded On
- 3/12/2024
- File Type
- Excel (XLSX)
- Description
- Table of the annual estimated spawning biomass of Pacific herring for each Puget Sound spawning area.
- Reporting Instructions
| Name | |
|---|---|
| Genetic Grouping |
Cherry Point, Cherry Point Baseline, Squaxin, Squaxin Baseline, All Other Herring Stocks Combined
[1 More Options]
All Other Herring Stocks Combined Baseline
|