PSP in Dungeness Crab in Alaska
Title: Life-threatening risk from paralytic shellfish poisoning in Dungeness crab in Southeast Alaska.
Bruce A. Wright¹, Elijah Donat², Ray RaLonde³
¹ APIA, 1131 E. International Airport Rd., Anchorage, AK, USA 99518-1408. (907) 222-4260, brucew@apiai.org
² Chilkat Environmental, PO Box 865, Haines, AK, USA 99827, (907) 303-7899, elijah@chilkatenvironmental.com
³Alaska Sea Grant, 1007 W. 3rd Ave. 100, Anchorage, AK, USA 99501. (907) 274-9697, afrlr@uaa.alaska.edu
Abstract
Paralytics shellfish poison (PSP) has been a pervasive problem in Alaskan shellfish. Primarily affecting bivalve shellfisheries, these industries must comply with sampling program requirements to protect human health. While these sampling efforts have been very successful in the commercial bivalve industry, Alaska does not have a program to monitor PSP for subsistence harvest. PSP from subsistence harvested shellfish continue to cause illnesses and fatalities. In 2010, for the first time in recorded history, a fatality of a Haines, Alaska resident occurred with consumption of Dungeness crab (Metacarcinus magister) viscera, often termed “crab butter.” Following the fatal incident, a collaborative investigation was conducted on Dungeness crab and blue mussels (Mytilus trossulus); mussels are a primary crab food source. Results revealed dangerous PSP toxin levels in mussels and Dungeness crab. Commercially harvested live untested Dungeness crab from beaches we tested are being shipped by air to markets on the Pacific putting people at risk of poisoning and even death.
Key Words
Paralytic shellfish poisoning, Dungeness crab, Metacarcinus magister, Southeast Alaska, harmful algal blooms
Introduction
Documented PSP fatalities in Alaska date back to 1799 when approximately 150 crew members of Alexander Baranof’s crew of the Russian American Trading Company died from PSP after eating blue mussels in Southeast Alaska (1). There have been many cases of illnesses and fatalities in Alaska from PSP toxicity since Baranof’s time.
Recent noteworthy occurrences of paralytic shellfish poisoning proliferated up the U.S. North Pacific Coast during spring and summer of 2010 from Washington (2), British Columbia (3), Southeast Alaska and continuing along the Gulf of Alaska coast to the Kodiak Islands (4) and the Aleutians Islands. PSP levels finally peaked in the Aleutian Islands by July 2010 (see Figure 1). In Alaska, three illnesses were reported on Kodiak Island from eating butter clams, one fatality occurred in the Juneau area from eating cockles Clinocardium sp. Another victim, in an unique case, was sickened from eating the viscera, commonly called crab butter, of Dungeness crab (4) harvested at Taiyasanka Harbor located 7 kms northeast of Haines, Alaska (see Figure 2). The Alaska Department of Health and Human Services-Epidemiology Section (ADHHS-ES) identified the illness as a case of PSP because the symptoms included paralysis and multiple resuscitations on the ‘life flight’ to Juneau. The victim partially recovered, was released and shortly thereafter died from heart failure, however, the State maintains the case as a PSP incident, and is the first recorded death in Alaska from consumption of crab viscera.
Bruce A. Wright¹, Elijah Donat², Ray RaLonde³
¹ APIA, 1131 E. International Airport Rd., Anchorage, AK, USA 99518-1408. (907) 222-4260, brucew@apiai.org
² Chilkat Environmental, PO Box 865, Haines, AK, USA 99827, (907) 303-7899, elijah@chilkatenvironmental.com
³Alaska Sea Grant, 1007 W. 3rd Ave. 100, Anchorage, AK, USA 99501. (907) 274-9697, afrlr@uaa.alaska.edu
Abstract
Paralytics shellfish poison (PSP) has been a pervasive problem in Alaskan shellfish. Primarily affecting bivalve shellfisheries, these industries must comply with sampling program requirements to protect human health. While these sampling efforts have been very successful in the commercial bivalve industry, Alaska does not have a program to monitor PSP for subsistence harvest. PSP from subsistence harvested shellfish continue to cause illnesses and fatalities. In 2010, for the first time in recorded history, a fatality of a Haines, Alaska resident occurred with consumption of Dungeness crab (Metacarcinus magister) viscera, often termed “crab butter.” Following the fatal incident, a collaborative investigation was conducted on Dungeness crab and blue mussels (Mytilus trossulus); mussels are a primary crab food source. Results revealed dangerous PSP toxin levels in mussels and Dungeness crab. Commercially harvested live untested Dungeness crab from beaches we tested are being shipped by air to markets on the Pacific putting people at risk of poisoning and even death.
Key Words
Paralytic shellfish poisoning, Dungeness crab, Metacarcinus magister, Southeast Alaska, harmful algal blooms
Introduction
Documented PSP fatalities in Alaska date back to 1799 when approximately 150 crew members of Alexander Baranof’s crew of the Russian American Trading Company died from PSP after eating blue mussels in Southeast Alaska (1). There have been many cases of illnesses and fatalities in Alaska from PSP toxicity since Baranof’s time.
Recent noteworthy occurrences of paralytic shellfish poisoning proliferated up the U.S. North Pacific Coast during spring and summer of 2010 from Washington (2), British Columbia (3), Southeast Alaska and continuing along the Gulf of Alaska coast to the Kodiak Islands (4) and the Aleutians Islands. PSP levels finally peaked in the Aleutian Islands by July 2010 (see Figure 1). In Alaska, three illnesses were reported on Kodiak Island from eating butter clams, one fatality occurred in the Juneau area from eating cockles Clinocardium sp. Another victim, in an unique case, was sickened from eating the viscera, commonly called crab butter, of Dungeness crab (4) harvested at Taiyasanka Harbor located 7 kms northeast of Haines, Alaska (see Figure 2). The Alaska Department of Health and Human Services-Epidemiology Section (ADHHS-ES) identified the illness as a case of PSP because the symptoms included paralysis and multiple resuscitations on the ‘life flight’ to Juneau. The victim partially recovered, was released and shortly thereafter died from heart failure, however, the State maintains the case as a PSP incident, and is the first recorded death in Alaska from consumption of crab viscera.
Figure 1. PSP levels in µg/100g in butter clams (Saxidomus giganteus) in the King Cove Lagoon, Alaska.
Figure 2. Study location; Taiyasanka Harbor (Lat. 59º 18’ 44.06” N. Lon. 135º 25’ 51.66” W).
Localized marine conditions such as stable vertical stratification with a surface freshwater lens and nutrients primarily from freshwater runoff are thought to be conditions that foster the Alexandrium blooms (5, 6). These conditions are common occurrences in Alaska that likely produce the species responsible for PSP. Focused localization of blooms could result in closely adjoining beaches having different PSP levels. This phenomenon appears to be the case in Alaska with the most numerous recorded PSP events occurring in specific locations in Southeast Alaska, around Kodiak Island, the Alaska Peninsula and in the eastern Aleutian Islands.
Materials and Methods
Rigorous testing for PSP in Alaska, using the Food and Drug Administration approved mouse bioassay, is exclusively performed by the Alaska Department of Environmental Conservation (ADEC) for commercial shellfish operations in Southeast and Southcentral Alaska. Subsistence caught bivalves and crab are not regularly tested for PSP in Alaska.
In response to the 2010 PSP illnesses in Taiyasanka Harbor, Alaska, the authors coordinated an investigation to assess the potential for PSP by collecting blue mussels the day after the fatality, June 19, 2010. The Abraxis ELISA screening method was used in 2010, providing presumptive results that prompted us to expand the study in 2011. For the 2011 study, we contracted with ADEC laboratory for PSP testing using the mouse bioassay procedure.
Tiayasanka Harbor is a small embayment with a total length of approximately 2.10 km and averaging 0.93 kms wide. The total area of the embayment is 325 hectares of which 144 are submerged marine waters. Maximum depth at a zero tide level is 38 meters. The bay exits into Chilkoot Inlet through a narrowed passage that is 58% narrower than the average width of the harbor, resulting in significant containment and isolation. The enclosed bay provides protection from storm events, making the harbor a frequently used anchorage and recreational area. To the north, Ferebee River provides significant freshwater influence and silt deposition into the harbor from Ferebee Glacier 21 kms to the north, forming fine-grained sediment deposits and a shallow mudflat that are good habitat for Dungeness crab. The predominant available prey is blue mussels covering much of the rocky intertidal shoreline and bottom of the natural harbor.
We selected the Taiyasanka Harbor study site for its simple food web and tight link between Dungeness crab, the readily available prey, blue mussels. Our 2010 study had investigated PSP in mussels and crab in both Taiyasanka Harbor and Letnikof Cove on the Chilkat Inlet to sample the locations where crab originated causing the PSP related death of the Haines man. Results identified only low levels on the Chilkat but identified Taiyasanka Harbor as a hot spot. The relatively isolated system is unique in that it likely provides a stable microscale gradient that allows Alexandrium sp. to thrive and persist (7). These conditions promote PSP hotspots, have been identified in a very few locations in Alaska, appear to be a result of unique geologies but offer a valuable opportunity for researching the many questions associated with Alexandrium sp. blooms that produce PSP in Alaska.
We also selected Taiyasanka Harbor because of the 2010 death associated with eating PSP contaminated crab, and Taiyasanka Harbor supports a commercial Dungeness crab fishery, a subsistence fishery for Haines residents, and a recreational fishery for visitors, mostly from Yukon Territory, Canada.
Sampling began June 17, 2011. One composite blue mussel tissue sample containing at least 5 mussels was collected every two weeks. The mussels were often small requiring up to 15 animals to obtain the 100 ml minimum sample volume required for PSP testing using the mouse bioassay. The two bi-monthly crab samples were composites of viscera from 2-3 male crab, but also from a single large male crab (8/29/11 and 9/11/11 samples). The crab traps were set within 5 meters of the location of six Dungeness crab traps and adjacent to rocky shoreline to be close to mussels in the harbor. Some of the mussel samples came from mussels entangled to the crab trap when raised from the harbor bottom. The soft tissue of the samples was collected in 150ml labeled jars, frozen and shipped within 2 days to the ADEC lab. The ADEC laboratory records indicate the samples remained frozen during the shipping.
Results
The test results show two consecutive years (2010 and 2011) with very high levels of PSP in mussels in mid-June in Taiyasanka Harbor, levels that are many times higher that the FDA limit of 80 µg/100g and were high enough to sicken or kill people. The 2010 mussel samples received confirmation testing with mouse bioassay testing and contained concentrations as high as 2,793 micrograms. The June 17, 2011 mussel sample exceeded 5,000 µg/100g, and decreased at each subsequent sampling event (see Figure 3). All 2011 Dungeness crab samples exceeded the FDA limit and peaked at 1,055 µg/100g on August 29, 2011 (see Figure 4).
Localized marine conditions such as stable vertical stratification with a surface freshwater lens and nutrients primarily from freshwater runoff are thought to be conditions that foster the Alexandrium blooms (5, 6). These conditions are common occurrences in Alaska that likely produce the species responsible for PSP. Focused localization of blooms could result in closely adjoining beaches having different PSP levels. This phenomenon appears to be the case in Alaska with the most numerous recorded PSP events occurring in specific locations in Southeast Alaska, around Kodiak Island, the Alaska Peninsula and in the eastern Aleutian Islands.
Materials and Methods
Rigorous testing for PSP in Alaska, using the Food and Drug Administration approved mouse bioassay, is exclusively performed by the Alaska Department of Environmental Conservation (ADEC) for commercial shellfish operations in Southeast and Southcentral Alaska. Subsistence caught bivalves and crab are not regularly tested for PSP in Alaska.
In response to the 2010 PSP illnesses in Taiyasanka Harbor, Alaska, the authors coordinated an investigation to assess the potential for PSP by collecting blue mussels the day after the fatality, June 19, 2010. The Abraxis ELISA screening method was used in 2010, providing presumptive results that prompted us to expand the study in 2011. For the 2011 study, we contracted with ADEC laboratory for PSP testing using the mouse bioassay procedure.
Tiayasanka Harbor is a small embayment with a total length of approximately 2.10 km and averaging 0.93 kms wide. The total area of the embayment is 325 hectares of which 144 are submerged marine waters. Maximum depth at a zero tide level is 38 meters. The bay exits into Chilkoot Inlet through a narrowed passage that is 58% narrower than the average width of the harbor, resulting in significant containment and isolation. The enclosed bay provides protection from storm events, making the harbor a frequently used anchorage and recreational area. To the north, Ferebee River provides significant freshwater influence and silt deposition into the harbor from Ferebee Glacier 21 kms to the north, forming fine-grained sediment deposits and a shallow mudflat that are good habitat for Dungeness crab. The predominant available prey is blue mussels covering much of the rocky intertidal shoreline and bottom of the natural harbor.
We selected the Taiyasanka Harbor study site for its simple food web and tight link between Dungeness crab, the readily available prey, blue mussels. Our 2010 study had investigated PSP in mussels and crab in both Taiyasanka Harbor and Letnikof Cove on the Chilkat Inlet to sample the locations where crab originated causing the PSP related death of the Haines man. Results identified only low levels on the Chilkat but identified Taiyasanka Harbor as a hot spot. The relatively isolated system is unique in that it likely provides a stable microscale gradient that allows Alexandrium sp. to thrive and persist (7). These conditions promote PSP hotspots, have been identified in a very few locations in Alaska, appear to be a result of unique geologies but offer a valuable opportunity for researching the many questions associated with Alexandrium sp. blooms that produce PSP in Alaska.
We also selected Taiyasanka Harbor because of the 2010 death associated with eating PSP contaminated crab, and Taiyasanka Harbor supports a commercial Dungeness crab fishery, a subsistence fishery for Haines residents, and a recreational fishery for visitors, mostly from Yukon Territory, Canada.
Sampling began June 17, 2011. One composite blue mussel tissue sample containing at least 5 mussels was collected every two weeks. The mussels were often small requiring up to 15 animals to obtain the 100 ml minimum sample volume required for PSP testing using the mouse bioassay. The two bi-monthly crab samples were composites of viscera from 2-3 male crab, but also from a single large male crab (8/29/11 and 9/11/11 samples). The crab traps were set within 5 meters of the location of six Dungeness crab traps and adjacent to rocky shoreline to be close to mussels in the harbor. Some of the mussel samples came from mussels entangled to the crab trap when raised from the harbor bottom. The soft tissue of the samples was collected in 150ml labeled jars, frozen and shipped within 2 days to the ADEC lab. The ADEC laboratory records indicate the samples remained frozen during the shipping.
Results
The test results show two consecutive years (2010 and 2011) with very high levels of PSP in mussels in mid-June in Taiyasanka Harbor, levels that are many times higher that the FDA limit of 80 µg/100g and were high enough to sicken or kill people. The 2010 mussel samples received confirmation testing with mouse bioassay testing and contained concentrations as high as 2,793 micrograms. The June 17, 2011 mussel sample exceeded 5,000 µg/100g, and decreased at each subsequent sampling event (see Figure 3). All 2011 Dungeness crab samples exceeded the FDA limit and peaked at 1,055 µg/100g on August 29, 2011 (see Figure 4).
Figure 3. PSP levels in µg/100g in mussels in Taiyasanka Harbor near Haines, Alaska from Jun 17, 2011 to Sept 11, 2011.
Figure 4. PSP levels in µg/100g in Dungeness crab in Taiyasanka Harbor, Lutak Inlet near Haines, Alaska from Jun 17, 2011 to Sept 11, 2011.
Discussion
The PSP levels in Dungeness crab were high throughout the testing period, but the 2011 PSP levels did not closely track the PSP levels seen in the mussels and results varied widely between samples taken on the same day and during the entire sampling period. The possible cause of the variability between PSP levels in mussels and crab may be due to the foraging and feeding behavior of predatory crabs with some crabs feeding on blue mussels while others consume various non toxin-baring food and/or breaks in feeding activity.
Historically, the occurrence of PSP in the viscera of Dungeness crab differs by region. In the commercial fishery around Kodiak Island and the southern Alaska Peninsula, PSP in crabs is a common occurrence; Dungeness crab are usually sold eviscerated and frozen; researchers have determined that Dungeness crab meat does not contain PSP, but the viscera can contain the toxin. Haines, Alaska has a productive commercial Dungeness crab fishery in the summer and commercial crab are harvested in Tiayasanka Harbor where the authors sampled. Most of the Haines crab harvest is shipped via air to markets in Seattle and along the U.S. west coast. These crabs are not regularly tested for PSP because it had not been demonstrated, until completion of this study, that toxin levels in Dungeness crab viscera presented a human health risk and warranted testing in Southeast Alaska.
Alaska Department of Fish and Game monitoring protocols call for a shutdown of the fishery or removal of the viscera if levels are encountered above 70µg/100g. While most people in Alaska discard the viscera, some do this after cooking and could still be exposed to PSP. Dungeness crab harvested in Southeast Alaska is also sold live and much of the market extends to Asia where people regularly eat the viscera and lipid layer under the carapace putting them at risk of poisoning. Shellfish products sold to markets outside of Alaska, due to the lack of investigation and incident reporting, could be causing illness or fatalities, which may include consuming Alaska Dungeness crab. This could be especially problematic where Alaska Dungeness crab is sold to Asian markets.
Determining PSP levels in Alaska shellfish and insuring the safety of crab harvests in Alaska is difficult because localized toxin levels are so variable. Differing sized and aged bivalves may have different PSP levels (8). Crabs are foraging species and PSP levels can vary considerable between crabs caught at the sample location and day of capture. For example, in the 1993-94 Dungeness crab PSP study in the Kodiak fishery, on June 12, 1992, three crabs captured at the same sampling site measuring below the 80 µg/100 gm while two others measured 196 and 313 µg/100 gm. On July 7, 1994 at East Point in the Kodiak fishery, crabs varied from a low of 330 to 1,608 µg/100 gm. In this study on August 29, 2011, two crabs measured 386 and 1,055 µg/100 gm.
Following an episode of PSP in crab viscera in Southeast Alaska in 1992 (Stromme 1995), the ADEC conducted extensive testing of crab viscera for PSP and domoic acid from all commercial species from 1993-94 (Table 1). Stromme (9), while working at Sitka Sound Seafood in Southeast Alaska, reported that crab testing during the 1992 season demonstrated the difficulty of finding PSP in Dungeness crab harvest with only a 3 crab of 311 tested over 80 µg./100 gm, ranging from 85-138 µg. The results of the study led to regulations requiring viscera removed prior to sale in the Dungeness crab harvested in the Kodiak fishery, but the low incidence in Southeast Alaska required only monitoring. With no positive results from the monitoring effort, required testing was terminated in 1998.
Table 1. Paralytic shellfish poison testing results in Alaska commercially harvested Dungeness crab 1993-94.
Sampling Total number Total number Percent
region tested positive positive
Southeast 867 13 1.5%
Yakutat 45 0 0.0%
PWS 54 0 0.0%
Cook Inlet 101 0 0.0%
Kodiak 391 109 27.9%
Total 1458 122 8.4%
Understanding Alexandrium sp. environmental requirements for producing PSP and toxin transfer dynamics between prey and crab predators requires controlled experiments. Laboratory experiments may provide some clues to the factors controlling the production and transfer of PSP through the ecosystem (prey to predator) (10), but we argue that researchers are as likely to resolve some of these questions in well designed studies in the few unique PSP hot spots such as Tiayasanka Harbor.
Conclusions
In 2011 this study found positive PSP results exceeding FDA limits for consumption in all eleven Dungeness crab samples taken over a nine week period demonstrating a localized and sustained PSP event. However, a monitoring program in Southeast Alaska, which encompasses over 15,000 miles of coastline, will likely yield few positive tests. We recommend an effort to investigate hot spots for PSP instead of furthering a geographically broad monitoring program. Hot spots should be identified and posted with signage, regularly sampled and the commercially harvested Dungeness crab either sold eviscerated or the crab fishery terminated in such embayments.
Consumers of commercial and subsistence Dungeness crab should be informed of safe consumption practices. Safe subsistence consumption is assured by cleaning before cooking and careful discard of viscera. Until hot spots are identified and these areas omitted from commercial harvest, when Alaska Dungeness crab are sold live to markets an education effort should precede sale so consumers are informed how they can avoid poisoning and Alaska can avoid liability risks. Precautionary labeling should be included with sales in the appropriate languages.
Acknowledgements:
The Environmental Protection Agency Indian Environmental General Assistance Program provided funds for this study. The co-authors have no conflict of interest to declare.
References:
(1) Tikhmenev, T.A., 1979. In: Pierce, R.A., Donnelly, A.S. (Eds.), A History of the Russian- American Company, Vol. 2, Documents. Period 1783–1807 (D. Krenov, Trans.). Limestone Press, Kingston, Ontario.
(2) Washington Department of Health. 2010. Shellfish Safety (updated 2012). http://www.doh.wa.gov/Portals/1/Documents/5500/EH-SF2011.pdf
(3) Fisheries and Oceans Canada. 2010. - Bivalve Shellfish: Marine Biotoxin Advisory - Widespread Closures on the B.C. Coast due to PSP. Fishery Notice. July 2, 2010.
(4) Alaska Health and Human Services. 2010. Paralytic Shellfish Poisoning in Juneau, Kodiak, and Haines, June 2010. State of Alaska Epidemiology Bulletin. No. 17.
(5) Smayda, T.J. 1997. Harmful algal blooms: Their ecophysiology and general relevance of phytoplankton blooms in the sea. Limnology and Oceanography 42:1137-1153.
(6) Ryan, J.P., H.M. Dierssen, R.M. Kudela, C.A. Sholin, K.S. Johnson, J.M. Sullivan, A.M. Fischer, E.V. Rienecher, P.R. Mcenaney, and F.P. Chavex. 2005. Coastal ocean physics and red tides. Oceanography 18:2.
(7) Stocker, R. 2012. Marine microbes see a sea of gradients. Science. Vol 38; pp628-633.
(8) Chambers, J.S., C.J. Carlson, n H.W. Magnuson. 1950. Variability of beds within individual bays. Technology studies on the Alaska butter clam, Saxidomus giganteus. Report of the Fisheries Product Laboratory, Ketchikan, Alaska.
(9) Stromme, G. 1995. PSP and the Alaska Crab Fishery. In Living with Paralytic Shellfish Poisoning: A Conference to Develop PSP Research and Management Strategies for Safe Utilization of Shellfish in Alaska (ed.) R. RaLonde and R. Painter. Alaska Sea Grant Program, Fairbanks, Alaska.
(10) Oikawa H, M. Satomi, S. Watabe, Y. Yano. 2005. Accumulation and depuration rates of paralytic shellfish poisoning toxins in the shore crab Telmessus acutidens by feeding toxic mussels under laboratory controlled conditions.