SUMMARY: May and June 2026 were marked by increased Pseudo-nitzschia activity in Central California, consistent with C-HARM predictions of high probabilities of Pseudo-nitzschia abundance and domoic acid (DA) concentrations exceeding alert thresholds in that region. Cal Poly Pier and Santa Cruz Wharf emerged as the two regional hotspots, with the smaller, less toxigenic “delicatissima” group at Cal Poly Pier reaching 2,658,986 cells/L on 5/10 and the larger, more toxigenic “seriata” group at Santa Cruz Wharf surging to 2,245,440 cells/L on 5/27, coinciding with the most elevated pDA detections of the period: 5,632 ng/L on 5/20 and 11,192 ng/L on 5/27.
Southern California stations recorded elevated but comparatively modest Pseudo-nitzschia activity through much of May before activity declined at most sites through June. Stearns Wharf recorded a particularly intense early May peak of 120,000-140,000 images/L (approximately 240,000-420,000 cells/L) by IFCB. IFCB data broadly corroborated HABMAP observations across the period and provided an important window into Northern California activity at Trinidad Pier, where Pseudo-nitzschia was detected at bloom levels in mid-June, consistent with C-HARM predictions for that region.
Alexandrium remained largely rare or undetected statewide, with low but persistent detections at Cal Poly Pier through May and June.
Fisheries Impacts: Elevated levels of DA detected in commercially harvested Pacific sardines and Northern anchovies from Central California waters in mid-June prompted state health agencies to recommend commercial fisheries restrictions implemented by CDFW, and CDPH to issue a consumption advisory for the recreational fisheries on 6/26.
Animal Impacts: A total of 19 marine mammal strandings with suspected DA exposure were reported across May and June, with Central California accounting for the majority of cases. Two humpback whales stranded on Monterey Bay beaches during this period, with very high DA levels detected in biological samples (see press release).
IMPORTANT NOTE: Pseudo-nitzschia activity continues to persist along the Central and Northern California coast. Trinidad Pier has recorded bloom-level Pseudo-nitzschia throughout August 10-17. Elevated DA was detected at both Humboldt and Santa Cruz, with mussel DA at both sites trending upward though currently below the 20 ppm CDPH alert level. On 7/31, the Del Norte razor clam recreational fishery was closed while the central California commercial sardine and anchovy fishery restrictions and recreational fishery advisory were lifted. Monterey Wharf recorded Pseudo-nitzschia at abundant levels on 8/12. Offshore, recent WCOA cruise observations confirmed high Pseudo-nitzschia between Point Conception and Monterey in July and August. Southern California sites are currently showing low Pseudo-nitzschia activity, with the HAB community dominated by dinoflagellates.
Read more in the full May-June 2026 HAB Bulletin report!
