2023 Marine Biotoxin Monitoring Annual Report
California Department of Public Health
Introduction
Historically, the majority of shellfish toxicity episodes have originated along the open coast, occasionally moving into bays and estuaries. Monitoring phytoplankton and mussels along the California coast is therefore essential for protecting the public that sport-harvests shellfish. Coastal monitoring also provides an early warning of toxic conditions that may soon impact shellfish in bays and estuaries, which harbor the majority of commercial shellfish growers and recreational clam beds.
Paralytic Shellfish Poisoning (PSP) and domoic acid poisoning (also referred to as amnesic shellfish poisoning or ASP) represent serious ongoing public health threats that require year-round attention. The California Department of Public Health (CDPH) manages a prevention program comprised of six elements: (1) a coastal phytoplankton monitoring program for early detection of toxin-producing species that could impact shellfish resources; (2) a coastal shellfish monitoring program that serves to protect recreational harvesters and acts as an early warning for harmful algal blooms (HABs) that could be transported into the bays and estuaries used for commercial shellfish aquaculture; (3) frequent toxin and phytoplankton monitoring of commercial shellfish growing areas; (4) an annual statewide quarantine on sport-harvested mussels (from May 1 through October 31); (5) mandatory reporting of disease cases; and (6) public information and education activities.
This annual report summarizes the monitoring effort and results for the PSP toxins, domoic acid, and toxigenic phytoplankton for 2023. A summary of quarantine and health advisory activities is also provided.
Materials and Methods
Detailed information on sampling protocols, analytical methods, and other aspects of the CDPH marine biotoxin monitoring program can be found in the program’s Management Plan for Marine Biotoxins in California Shellfish, available upon request. The following is a brief summary of the materials and methods used for routine monitoring of phytoplankton and shellfish.
Shellfish Sampling
Mussel samples are routinely collected at one or more representative sampling stations in each coastal county. These coastal samples serve to protect the public that harvests shellfish recreationally and also act as an early warning for recreational (e.g., clamming) and commercial shellfish harvesting inside bays and estuaries.
Sea mussels (Mytilus californianus) are the predominant species collected along the coast, with bay mussels (M. galloprovincialis) more prevalent in calmer waters (bays, estuaries, marinas) and commercial aquaculture leases.
Coastal mussel samples are collected at least monthly by a number of participating agencies and volunteers. CDPH requests additional samples based on observed toxicity or the presence of a toxin-producing species of phytoplankton in the region. Coastal sampling is usually limited to two intervals per month when the daytime low tide is sufficiently low to allow safe access to mussel beds.
A valuable adjunct to the sampling of natural mussel populations is the use of sentinel mussels: plastic mesh bags filled with mussels and suspended from a pier or buoy. Both sea mussels and bay mussels may be used for this purpose. Samples from sentinel mussel bags can be retrieved regardless of tides and ocean conditions, providing a valuable tool for both routine and emergency response monitoring.
Commercial shellfish harvesting in California is conducted on private tidelands or aquaculture leases granted by state or local authorities. Commercial shellfish growing areas are sampled at least weekly. Sentinel mussels are strategically located in most commercial growing areas as an early warning tool; they can be retrieved regardless of tidal conditions and are often safer than sampling intertidal populations. In some cases there are natural sets of mussels in the desired location (e.g., on pilings) that can serve the same purpose. In most growing areas oyster samples from representative locations are also submitted weekly.
Shellfish sample handling and preparation is conducted following the CDPH sampling protocol provided to all collectors. This protocol is based on National Shellfish Sanitation Program (NSSP) requirements. A shellfish sample consists of at least 15-20 individuals, more if necessary, to provide a minimum of 250 grams (g) of tissue. In the case of certain larger or difficult to obtain recreational species (e.g., gaper clams and razor clams, respectively), fewer individuals may be collected to assess potential immediate risk to sportharvesters. Individual shellfish are cleaned of exterior sand and debris, opened while avoiding tissue damage and the byssal threads removed as needed, drained of excess liquid, and placed in a sample bottle provided by CDPH. The sample is immediately refrigerated, typically in an ice chest with ice packs (i.e., ‘blue ice’) and maintained at 0-10° during transport back to the collector’s base, where it is immediately frozen. The frozen sample and completed sample submission form are packaged and shipped to the CDPH laboratory in Richmond via 24-hour courier in an insulated shipping container provided by CDPH.
The CDPH Microbial Diseases Laboratory conducts PSP assays following the American Public Health Association (1970) methodology recognized by the NSSP. Samples are homogenized and extracted, with the majority of mussel sample screened for toxin presence/absence via a lateral flow immunoassay (Neogen Reveal 2.0). Negative samples do not require further testing. Positive mussel samples and samples of all other shellfish species are immediately tested with the mouse bioassay (APHA, 1970). The assays used report the total toxicity of a sample, consisting of saxitoxin (STX) and the various analogs that may be present. Data is therefore reported as micrograms of saxitoxin equivalents per 100 grams of tissue (µg STX eq./100 g). The PSP alert level is ≥ 80 µg STX eq./100 g of shellfish tissue and the laboratory’s detection limit ranges from 32 to 37 µg STX eq./100 g.
A subset of samples arriving each day are split after homogenization, with a portion of the sample being directed to the CDPH Food and Drug Laboratory for domoic acid analysis by high performance liquid chromatography (Dhoot, 1993; Quilliam, 1995). Staff of the marine biotoxin monitoring program determine which samples to analyze for domoic acid based on current trends in the presence and relative abundance of Pseudo-nitzschia, the detection of this toxin in shellfish from the region, or representative regional monitoring. Higher risk offshore areas have routine monitoring. The domoic acid alert level is ≥ 20 µg/g (= 20 parts per million [ppm]) and the laboratory’s minimum reporting limit is 2.5 ppm.
Phytoplankton Sampling
Phytoplankton samples are primarily collected from coastal piers, with some samples collected from the surf zone, boat docks, and offshore via vessel.
Qualitative samples are collected with a plankton net provided to each collector. Standardized equipment used by CDPH consists of a 1 meter length conical nylon mesh net, 25 centimeters wide at the mouth, with a 20 µm mesh size and a collecting bucket at the cod end to contain the concentrated sample. Vertical net tows are conducted at most sites, although horizontal tows are necessitated by shallow water sites. A standard tow consists of a total tow length of 50 feet (e.g., five vertical net retrievals in 10 feet of water). Adjustments can be made for deeper water sites (e.g., a single tow at 50 feet); collectors are advised to examine the sample and, if clear, do additional tows to increase the cell mass. The depth sampled and total tow length are recorded by the sampler.
For sandy beach surf zones (e.g., some coastal sites in Del Norte and Humboldt counties), volunteer samplers collect buckets of seawater and pour these through a supported net.
An estimate of the total volume sampled is recorded by the sampler. Each sample is thoroughly mixed before decanting into a sample bottle containing a small amount of fixative. The sample bottle and sample collection form are placed in a shipping canister and sent to the CDPH laboratory in Richmond. Marine Biotoxin Monitoring Program staff conduct all sample observations. A wet mount slide is prepared for each sample and observed using standard light microscopy. All cells present are identified to genera, with identification to species when possible, and an estimate made of the percent composition of each. A simpler abundance scale was developed primarily for use by volunteers trained to conduct field observations, consisting of the following ranks: Rare (< 1%), Present (1-9%), Common (10-49%), and Abundant (≥ 50%).
Estimates of abundance based on percent composition can be misleading because they do not account for varying cell densities (e.g., cells per liter of seawater) or sampling effort (i.e., the depth of water sampled and the number of times the phytoplankton net is retrieved through that depth). To adjust for the importance of cell mass and sampling effort, a Relative Abundance Index (RAI) was formulated[1]. The RAI data can provide perspective on the significance of the percent composition data for the species of interest.
[1] The RAI is based on an estimate of cell mass as determined by settled cell volume (a), the percent composition of each species (b), and the sampling effort as determined by the total tow length (c; this is the depth sampled multiplied by the number of net retrievals over that depth)): RAI = (a*b)/c
Results
2023 Sampling Effort: Paralytic Shellfish Poisoning
Shellfish samples were collected at 70 different sites along the coast of California in 2023 for PSP toxin testing. Not all commercial sampling sites are shown due to the scale of the maps: several growing areas have multiple sampling sites, representing different harvest areas, within a small area.
There were 839 shellfish samples collected statewide for PSP toxin assay during 2023. The greatest number of samples (198) was collected at sites in Marin County; 85% of these samples were associated with commercial shellfish aquaculture companies operating in Tomales Bay.
Statewide, commercial shellfish growers accounted for 60% of all samples collected in 2023, followed by various state agencies and universities, citizen volunteers and educational nonprofit organizations, coastal county health departments, and federal and tribal agencies (18%, 12%, 5%, and 5%, respectively).
The majority of samples collected in 2023 consisted of mussels (78%), followed by Pacific oysters (21%). The Marine Biotoxin Monitoring Program uses mussels as a primary indicator species for PSP toxins because of their ability to bioaccumulate these toxins at a faster rate than other bivalve species (Shumway, 1990). Differential uptake in mussels versus oysters during a major PSP event in California was previously documented, with sentinel oysters accumulating only 12 to 35% of the total toxin concentration found in sentinel mussels (California Department of Health Services, 1991).
2023 Sampling Effort: Domoic Acid
Many of the samples arriving at the CDPH laboratory for PSP testing are also analyzed for domoic acid. Shellfish samples from 56 different sampling sites were targeted for domoic acid analysis as a result of observations of elevated numbers of Pseudo-nitzschia spp. in samples from the volunteer monitoring network, as routine shellfish monitoring samples, or as a follow-up to a previous positive sample.
There were 400 bivalve shellfish samples analyzed for domoic acid during 2023, with 49% of these samples originating from commercial aquaculture companies. Citizen volunteers and nonprofit organizations also accounted for a significant number of domoic acid samples (18%). The greatest numbers of samples were submitted from the counties of Santa Barbara (113, 28%), San Luis Obispo (63; 16%), Humboldt (59; 15%), and Del Norte (52; 13%). Mussels, oysters, and razor clams accounted for the majority of these samples (60%, 25%, and 14%, respectively).
2023 Sampling Effort: Phytoplankton
There were 1092 phytoplankton samples collected during 2023 by our volunteer-based monitoring effort. These samples were collected by 70 samplers at 120 sites representing all 15 coastal counties and two interior counties bordering San Francisco Bay. A number of organizations collect samples in multiple counties and several areas (e.g., commercial shellfish growing areas) have multiple sites that are not individually identified in the figures.
The distribution of toxin-producing species (Alexandrium and Pseudo-nitzschia) was widespread. Alexandrium was observed at 55 different sampling sites representing all coastal counties sampled, except Del Norte, including two interior counties bordering San Francisco Bay. Pseudo-nitzschia was observed at 91 sampling sites representing all coastal counties and the same two San Francisco Bay counties. Of the 1092 phytoplankton samples collected in 2023, 536 (49%) contained one or more toxigenic species. The percentage of total samples containing one or more toxin-producing species, by coastal county, ranged from 27% (Del Norte County) to 71% (Marin County).
Inside San Francisco Bay, there was a higher percentage of samples with toxigenic species in Contra Costa (59%) than in adjacent Alameda County (9%). This was an artifact of sampling, as the majority of the latter samples was collected at a location with limited marine influence.
2023 Monitoring Results:
The following is a brief summary of major trends in the distribution and relative abundance of toxic phytoplankton and the associated distribution and magnitude of marine biotoxins in shellfish. More detail can be found in the monthly reports produced by the CDPH Marine Biotoxin Monitoring Program. The monthly reports contain detailed maps of shellfish toxin and phytoplankton data that illustrate the weekly domoic acid and PSP toxin concentrations and the distribution and relative abundance of Alexandrium and Pseudo-nitzschia. In addition, information is provided on the current status of quarantines and health advisories and lists of program participants are provided. These reports are available at the following Internet site:
2023 Monitoring Results: Alexandrium Observations and Paralytic Shellfish Poisoning Toxicity
Alexandrium occurred in 175 of the 1092 phytoplankton samples (16%). For those counties exceeding the median number of samples (65), the highest frequency of occurrence for Alexandrium was observed in San Luis Obispo (26%), Marin (24%), and Santa Cruz (20%).
Observations of Alexandrium were recorded in each month of the year at multiple sites along the California coast. Slight increases in the percent composition of Alexandrium were observed in mid-May at several sites. The relative abundance of this dinoflagellate continued to increase through early July, declining to lower percentages by August. A second increase in Alexandrium percent composition occurred in late August, peaking in mid-September and declining to background levels by October.
The pattern of increase in Alexandrium percent composition in July and August involved a number of disparate sites rather than a sustained pattern of increase and decrease in one geographical area.
The majority of Alexandrium observations occurred at sites in San Diego (30), San Luis Obispo (28), and Marin (20) counties. The greatest percent composition of Alexandrium was observed in mid Morro Bay, San Luis Obispo County (15%, July 5). Alexandrium was also common (10%) in several subsequent samples: Richmond Marina Bay (Contra Costa County) inside San Francisco Bay (July 20), at two sites offshore of San Francisco (July 21 and 25), and in mid Morro Bay (September 5).
The majority of samples with an elevated percent composition of Alexandrium were not associated with significant increases in cell mass. The few occurrences of increased cell mass, as determined by the relative abundance index (RAI), occurred between July and September.
The July 5 mid Morro Bay sample with 15% Alexandrium also had a modest increase in cell mass. The next occurrence of an elevated RAI was not until August 30 at the Pacifica Pier (San Mateo County), followed by a September 17 sample at the Drakes Bay sentinel mussel station (Marin County).
In general, the relative abundance of Alexandrium was low, with 126 of the 175 observations ranked as “Rare” (71%) and 48 as “Present” (27%).
PSP activity in 2023 was similar to 2022 and considerably reduced compared to the eight years prior to 2021.
Of the 839 shellfish samples collected in 2023, 130 (15%) contained PSP toxins, with 10 of those exceeding the alert level. PSP toxicity was detected in shellfish from each coastal county between Del Norte and San Diego counties, with the exception of Los Angeles and Orange.
Low levels of PSP toxins were detected through most of January, then subsided until the beginning of May. PSP toxicity in shellfish samples exceeded the alert level from July to the beginning of August, with a separate single peak in mid-September. Low toxins levels continued to be detected through the end of the year.
There was a northward progression of PSP toxins in shellfish, with the first positive samples in Santa Barbara (January), progressing through San Luis Obispo (early June), Santa Cruz (late May), Marin and Sonoma (early July), and Humboldt (early August). Note: the above counties had the greatest number of total, as well as PSP-positive, samples. Other counties with fewer samples (see previous table) exhibited variations to this general pattern of toxicity onset.
San Luis Obispo County had the greatest number of shellfish samples exceeding the PSP alert level. Low toxin concentrations were first detected in mussels from the Cal Poly Pier (44 µg STX eq./100 g, June 5) and Montana de Oro State Park (43 µg STX eq./100 g, June 7). By early July these toxins were also detected in oysters from inner Morro Bay (67 µg STX eq./100 g, July 5), coinciding with a significant increase at Montana de Oro State Park (311 µg STX eq./100 g, July 6). Oysters inside Morro Bay exceeded the alert level briefly (108 µg STX eq./100 g, July 17), declining below the alert level by July 19. PSP toxicity declined below the alert level by mid-August, with a singular spike in mussels at the Cal Poly Pier on September 18 (293 µg STX eq./100 g). Toxicity remained at low levels along the San Luis Obispo coast through December.
2023 Monitoring Results: Pseudo-nitzschia Observations and Domoic Acid Toxicity
Pseudo-nitzschia was observed in 455 of the 1092 phytoplankton samples collected (42%), representing all coastal counties as well as two counties bordering the east shore of San Francisco Bay. This diatom was also observed in samples from multiple counties during each month of the year.
Of the 455 observations of Pseudo-nitzschia, 213 were ranked as “Rare”, 155 as “Present”, 74 as “Common”, and 13 as “Abundant”.
The “Common” occurrences of Pseudo-nitzschia were observed at 35 different sampling locations representing all coastal counties except Mendocino and Ventura. “Abundant” occurrences of this diatom were observed at 13 different sampling sites in nine counties: Humboldt, San Mateo, Santa Cruz, Monterey, Santa Barbara (including offshore at Santa Cruz Island), Ventura, Los Angeles, Orange, and San Diego.
Of the 400 samples analyzed for domoic acid, 55 had detectable concentrations: 47 razor clam samples, four sea mussel samples, two bay mussel samples, and two Pacific oyster samples. There were 15 razor clam samples that exceeded the alert level, ranging from 20 to 59 ppm; one sample each of cultured bay mussels and Pacific oysters also exceeded the alert level (31 and 29 ppm, respectively).
The magnitude of domoic acid in shellfish remained low during 2023, comparable to the previous two years and significantly reduced from years prior to 2021.
The percent composition of Pseudo-nitzschia increased in late February through June. A separate, brief increase was also observed at the end of September.
The elevated percent compositions of Pseudo-nitzschia observed between February and June occurred mostly at southern California sites. Moving northward, there were increases in this diatom in May between Monterey and San Mateo counties.
There was a brief but significant increase in Pseudo-nitzschia percent composition in late September at sampling sites in Humboldt Bay and in northern Del Norte County, extending into October for the former location.
Despite the elevated percent composition of Pseudo-nitzschia at southern California sites between early spring and early summer, the cell mass, as represented by the relative abundance index, remained low, with the exception of a single early March sample. In contrast, the fall increase in percent composition was accompanied by significant increases in cell mass.
The early spring increase in cell mass, noted above, occurred offshore of Orange County in Santa Catalina Channel.
The fall increases in Pseudo-nitzschia cell mass occurred at sites in Humboldt and Del counties.
The elevated domoic acid concentrations detected in razor clams at the end of 2022 persisted through May, finally decreasing below the alert level by June. On June 12 there was a spike in domoic acid in aquacultured mussels and oysters offshore of Santa Barbara. By late October the domoic acid concentration increased above the alert level in razor clams, similar to the fall increase in northern California the previous year.
The elevated levels of domoic acid in winter and spring occurred in razor clams from both Del Norte (Crescent Beach) and Humboldt (Clam Beach) counties. Toxin concentrations declined at both sites at approximately the same time. The fall increase in domoic acid occurred in razor clams from Del Norte, with mussels and razor clams from Humboldt sites exhibiting a much lower concentration of this toxin. Unfortunately, inadequate tides and scarcity of razor clams prevented the collection of additional razor clam samples through the remainder of the year. Sport-harvesting of razor clams in Del Norte County was prohibited during this time (see the health advisory details below).
The June increase in domoic acid in aquacultured mussels and oysters offshore of Santa Barbara and the high cell mass of Pseudo-nitzschia observed in Santa Catalina Channel coincided with the reported strandings and deaths of thousands of marine mammals in southern California through June.
CDPH would like to acknowledge the tremendous help provided by the Tolowa Dee-ni’ Nation and volunteer Ken Graves in providing razor clam samples from Del Norte County, and volunteers Jack Foster and Mario Minder for providing razor clams and a Washington clam sample, respectively, from Humboldt County. Their efforts were essential for monitoring toxin levels and protecting the public from gathering and consuming highly toxic shellfish.
Quarantines, Health Advisories, and Reported Illnesses
Annual Mussel Quarantine
CDPH issues the annual quarantine on sport-harvesting of mussels for human consumption on May 1, which normally extends through October 31. Toxin activity outside of the normal quarantine period may result in an early start or an extension to the quarantine. The annual mussel quarantine applies only to sport-harvested mussels along the entire California coastline, including all bays and estuaries. Routine biotoxin monitoring is maintained throughout the quarantine period. Additional health advisories are issued for other affected species when toxins are detected at dangerous levels. The annual quarantine does not affect the certified commercial shellfish growing areas in California. Shellfish sold by certified harvesters and dealers are subject to frequent mandatory testing, with harvest closures directed by CDPH as needed.
Health Advisories
• On December 12 CDPH lifted the paralytic shellfish poisoning toxins shellfish advisory related to sport-harvested mussels, scallops, and clams in San Luis Obispo County.
• On November 20 CDPH lifted the paralytic shellfish poisoning toxins shellfish advisory related to sport-harvested mussels, scallops, and clams in San Mateo County.
• On November 9 CDPH issued a health advisory warning consumers not to eat sport-harvested razor clams from Del Norte County due to dangerous levels of domoic acid in samples collected at the end of October.
• On October 27 CDPH announced that the annual mussel quarantine would end at midnight, October 31 for all counties except San Mateo and San Luis Obispo.
• On September 7 CDPH issued a health advisory warning consumers not to eat sport-harvested mussels, clams, or scallops from Mendocino County due to dangerous levels of the paralytic shellfish poisoning toxins in shellfish samples.
• On August 3 CDPH lifted the domoic acid shellfish advisory related to sport-harvested razor clams in Humboldt County.
• On August 1 CDPH lifted the domoic acid shellfish advisory related to sport-harvested mussels, scallops, and clams in Santa Barbara County.
• On July 28 CDPH issued a health advisory warning consumers not to eat sport-harvested mussels, clams, or scallops from San Mateo County due to dangerous levels of the paralytic shellfish poisoning toxins in shellfish samples.
• On July 14 CDPH issued a health advisory warning consumers not to eat sport-harvested mussels, clams, or scallops from San Luis Obispo County due to dangerous levels of the paralytic shellfish poisoning toxins in shellfish samples.
• On July 6 CDPH lifted the shellfish advisory related to sport-harvested razor clams in Del Norte County. The advisory was due to dangerous levels of naturally occurring domoic acid, also referred to as Amnesic Shellfish Poisoning. Razor clams have been continually tested and have now met the criteria for lifting the safety notification in Del Norte County. An advisory for razor clams in Humboldt County remains in effect.
• On June 16 CDPH advised consumers not to eat sport-harvested mussels, clams, or scallops from Santa Barbara County due to the presence of dangerous levels of domoic acid in shellfish samples.
• On May 1 CDPH initiated the annual quarantine of sport-harvested mussels gathered along the California coast. The quarantine normally extends from May 1 through October 31, although elevated toxin levels can extend the quarantine period. This annual quarantine applies to all species of mussels that are recreationally harvested for human consumption along the California coast, including all bays and estuaries. The quarantine is in place to protect the public from poisoning that can lead to serious illness, including coma and death.
• On January 9 CDPH rescinded the October 27, 2022, advisory for sport-harvested mussels, scallops, and most types of clams in Humboldt County. An advisory for razor clams in Humboldt County remains in effect.
Reported Illnesses and Deaths
There were no reported illnesses or deaths associated with either PSP or domoic acid in 2023.
Additional Information
CDPH Office of Public Affairs press releases for the above health advisories:
CDPH Food and Drug Branch domoic acid health advisories for Dungeness and rock crab:
Acknowledgements
The information in this report represents the efforts of many individuals, including program participants that collect shellfish and phytoplankton samples; California Department of Public Health (CDPH) laboratory scientists responsible for domoic acid and paralytic shellfish poisoning testing; environmental scientists in the CDPH Preharvest Shellfish and Marine Biotoxin Monitoring Program that manage the monitoring programs and examine phytoplankton samples; food inspectors in the CDPH Food and Drug Branch that collect a variety of seafood samples during a biotoxin event; communications experts in the department’s Office of Public Affairs who issue press releases to alert and educate the public; and many others that support these efforts. All of those involved in the CDPH Marine Biotoxin Monitoring Program play a vital role in protecting the public’s health.
CDPH would like to thank the California Department of Fish and Wildlife for their support of a portion of the paralytic shellfish poisoning monitoring effort of the Marine Biotoxin Monitoring Program. This program provides protection and guidance to sportharvesters and commercial shellfish growers. The CDPH Marine Biotoxin Monitoring Program would also like to acknowledge the dedicated work and expertise of the scientists of the Department’s Microbial Diseases Laboratory and the Food and Drug Laboratory for their efforts in conducting PSP assays and domoic acid analyses, respectively. Due to the unpredictable nature of marine biotoxin activity, the laboratories are often called upon to respond immediately to an influx of samples resulting from these events. It is due to their efforts that we are able to provide rapid feedback to field samplers and notify the public of potential health risks.
Shellfish toxicity data are generated on a daily basis by the Marine Biotoxin Monitoring Program thanks to the continuing efforts of our program participants. Additionally, volunteers are collecting phytoplankton samples on a routine basis, increasing their sampling frequency during periods of concern and providing near real-time observations of the occurrence of toxin producing species. These efforts are critical to our ability to monitor phytoplankton distribution and abundance along the California coast. As with all such endeavors, our success in protecting the public is due in large part to the numerous people who contribute their time and effort to collect samples at representative sites along the coast. The listing of our program participants, provided in each monthly report and in this annual report, illustrates the diversity of groups and individuals that contribute to these efforts.
We would like to express our sincere appreciation to our program participants for all of their efforts. It is through their active participation that CDPH is able to protect and improve the health of all Californians.
The following is a list of program participants that collected shellfish samples during 2023:
The following is a list of program participants that collected phytoplankton samples during 2023:
References
American Public Health Association, 1970. Recommended Procedures for the Examination of Sea Water and Shellfish, 4th Edition, APHA, New York, N. Y.
California Department of Health Services Marine Biotoxin Monitoring Program, 1991. Shellfish biotoxin monitoring program annual report, 1991, 50 pp.
California Department of Public Health, Monthly Biotoxin Monitoring Program reports, 2019.
Dhoot, J.S.; del Rosario, A.R.; Appel, B.R.; Tamplin, B.R.1993. An improved HPLC procedure for domoic acid analysis in seafood, Int. J. Environ. Anal. Chem. Volume 53, 4, 269-279.
Quilliam, M.A., Xie, M., and Hardstaff, W.R. 1995. Rapid extraction and cleanup procedure for the determination of domoic acid in tissue samples. NRC Institute for Marine Biosciences, Technical Report #64, National Research Council Canada #33001. Journal of AOAC International, 78: 543–554.
Shumway, S. E. 1990. A review of the effects of algal blooms on shellfish and aquaculture, J. World Aquaculture Soc., 21: 65 – 104.
