HABs — A Deeper Look
Interactive HABs Map
Scientists and resource managers use various methods to assess harmful algal blooms (HABs). Public health monitoring of HAB toxins in shellfish has been conducted for more than 15 years along the U.S. West Coast. Since HAB occurrences differ in location, size, and duration each year, this long-term data provides a historical context that helps predict the potential impacts of HABs in any given year. For this indicator, the status of HABs is determined by the reduction in shellfish harvesting opportunities caused by HAB toxin contamination.
Marine mammal strandings related to HABs are also considered when evaluating HAB impacts, though they are not included in the status and trend determinations due to uncertainties in the data. Adult female California sea lions, Guadalupe Fur Seals, and Northern Fur Seals are used as a representative demographic of three marine mammal species for stranding events, as previous studies have shown this group can reflect the broader effects of domoic acid on the coastal marine mammal population. A probable event is defined as years in which the stranding rate of HAB indicator species exceeds the historical average.
What is the recent status of HABs across the US West Coast?
Status
The coast-wide status for the most recent year was assessed as Meeting Expectation. Roughly 20% of the counties/zones are above historical expectation. The coast-wide average impaired opportunity of all counties/zones was 42% for recreational harvesting opportunities and 33% for commercial harvest opportunities.
This figure shows...
HAB Impaired Shellfish Harvesting Opportunity for individual counties/fishing zones along the U.S. West Coast for commercial and recreational harvesting activities. HAB Impaired Harvest Opportunity is assessed as the percent of lost days relative to the historical baseline for each sector. The historical baseline is the average percentage of impaired days between 2009-2023.
Although HAB impacts to shellfish harvest opportunities were typical this year, the effect of HABs was observed on marine mammals along the U.S. West Coast this year. Marine mammals, particularly in Southern California, were negatively impacted by the HAB toxin, domoic acid.
This figure shows...
the count of strandings of marine mammals that are sentinels for domoic acid HAB events, Adult Female California Sea Lions and Fur Seals in 2023. The historical baseline is the average percentage of the indicator demographic from 2006-2023 for each state.
How does the status of HABs compare among states?
California
- Overall, impaired opportunity in California was on par with the historical average
- Recreational lobster harvest was notably impacted by HAB toxins this year
- Marine mammal strandings were elevated in southern California due to domoic acid.
Oregon
- Overall, impaired opportunity in Oregon was on par with the historical average.
- Commercial and recreational Dungeness crab harvesting was the most impacted by HABs this year.
- Marine mammal strandings were on par with historical expectations.
Washington
- Overall, impaired opportunity in Washington is slightly above the historical average.
- Recreational harvest of razor clams and commercial Dungeness crab harvest were most impacted by HABs.
- Marine mammal strandings were on par with historical expectations.
This figure shows...
HAB Impaired Shellfish Harvesting Opportunity for each subregion of the U.S. West Coast. The panel on the left shows impaired opportunity for the recreational sector and the panel on the right shows impaired opportunity for the commercial sector. The dashed line is the historical average for each subregion and points are individual counties or harvest zones.
This figure shows...
HAB Impaired Shellfish Harvesting Opportunity for each species of interest, with each species represented by a different colored bar. The asterisk in the legend identifies species that are not present along the entire range of the West Coast.
This figure shows...
the percent of the marine mammal species that are indicators of HAB events relative to the historical average. The dashed line is the historical average normalized to zero percent for each subregion of the U.S. West Coast.
How does this year compare to others?
2023 was a typical year for HAB Impaired Shellfish Harvest Opportunity.
This figure shows...
a timeseries of the percent of HAB Impaired Shellfish Harvest Opportunity along the U.S. West Coast. The dashed black line shows the combined long-term average of HAB Impaired Opportunity.
Regionally, HAB events have impacted marine mammals in Southern California more than normal in 2023.
This figure shows...
historical counts of strandings of HAB sentinel marine mammals species (Adult Female California Sea Lions and Fur Seals) across the U.S. West Coast. The historical baseline is the average percentage of the indicator demographic from 2006-2023 for the full coastline.
How are HABs changing across the US West Coast?
Trends
Changes in coast-wide HAB Impaired Shellfish Harvest Opportunity are assessed as having No Trend. The vast majority of counties/zones, three-quarters, have no significant long-term or recent trend.
There are more counties/zones with significant increasing trends than those that are decreasing.
This table shows...
the percent of coastal counties/zones along the U.S. West Coast that have No Trend, are Increasing or are Decreasing over 15 years of HAB toxin monitoring in shellfish. Trends are determined based on a linear fit of the annual data.
How do trends in HABs compare among states?
As a percent of coastal counties or harvest zones, the majority of counties/state in all states are exhibiting no 15-year trend. However, for the 15-year trend, there are both increases and decreases in each state, with more increasing trends.
These pie charts show...
the percent of coastal counties/zones within each state that have HAB Impaired Shellfish Harvest Opportunity with No Trend, Increasing or Decreasing over 15 years. Trends are determined based on a linear fit of the annual data in the maximum extent of kelp canopy coverage for individual coastal segments.
What is the magnitude of the trends?
While the majority of coastal counties or coastal harvest zones show no long-term (15-year) trends, there are counties/zones in each state exhibiting both increases and decreases. The magnitude of change for those segments that are increasing are between 0.2 – 0.8% per year. The magnitude of change for those counties/zones that are decreasing also falls within the same range (-0.2 to -0.8% per year). However, there are not only more counties/zones undergoing increases, but also a few segments undergoing increases greater than 1% per year. Of those, they are all within California.
This figure shows..
the slope of the 15-year trend for all coastal counties or coastal harvest zones along the U.S. West Coast categorized by state. (California – blue circles; Oregon – orange circles; Washington – green circles). If the linear fit was nonsignificant (alpha = 0.05), the slope is reported as zero. There are overlapping data points on the no trend, zero line.
Trend Story:
An example from an individual
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