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Seafood Safety

Is it risky to eat the seafood from the bay? To citizens of Texas and the Galveston Bay region, this is a compelling question. News accounts of bay-related health threats get a lot of attention from the media and the public. For example, contamination in Upper Galveston Bay and its tributaries has led to an advisory from the Texas Department of State Health Services (TDSHS) to avoid certain seafood taken from that area. Similarly, large areas of the bay are closed to shellfish harvesting due to potential risk to consumers from pathogens.

There are various types of risk to human health that may be associated with using the bay. Public health risks are placed in three categories: pathogens, such as the bacteria that cause infection; toxicants, such as dioxins or mercury; and other risks, such as drowning. To minimize risks to human health, state and federal agencies conduct risk assessments and monitor water and sediment quality.  The data support management strategies, such as the classification of shellfish harvest areas and the issuance of seafood consumption advisories.

Seafood Consumption Advisories

Seafood consumption advisories are issued by the TDSHS under the Aquatic Life Law. When indications of a risk to human health are brought to the agency's attention, a risk assessment is conducted. If a risk assessment indicates an imminent health hazard, the affected area is declared ‚ÄúProhibited‚ÄĚ for affected species, and taking those species from the area becomes a violation of law. An imminent hazard exists if just one or a few meals would result in an acute health problem. If a less immediate hazard exists, one created by longer-term consumption habits, a ‚ÄúConsumption Advisory‚ÄĚ is issued with consumption recommendations for affected populations.

Six seafood advisories have been issued for the Galveston Bay system since 1990 and five of them are in effect:

  • ADV-3, issued in 1990, recommends that catfish and blue crabs from the Houston Ship Channel be consumed at one meal per week or not at all if the consumer is a pregnant woman or child.
  • ADV-20, issued in 2001, recommends that consumption of any fish from the Houston Ship Channel be limited as described in ADV-3.
  • ADV-28, issued in 2005, recommends that consumption of spotted seatrout in the upper portion of Upper Galveston Bay be limited as described in ADV-3.
  • ADV-35, issued in 2008, recommends that spotted seatrout and all species of catfish from any location in Galveston Bay be consumed at one meal a week and that pregnant women and children consume none due to the risk associated with dioxin/furan and PCB levels.
  • ADV-37, issued in 2009, recommends that fish from Clear Creek not be consumed at all due to PCB contamination.

  

Table 1.  Seafood consumption advisories issued by the TDSHS for Galveston Bay since 1990.

Year Area Species Contaminant
1990 Houston Ship Channel, Upper Galveston Bay

Catfish and blue crab

(Map) (Advisory)

Dioxin
1993 Clear Creek (rescinded in 2001)

Catfish and blue crab

(Map) (Advisory)

Volatile organic compounds (VOCs), chlordane
2001 Houston Ship Channel (between Lynchburg Ferry and Highway 90 Bridge)

All species of fish

(Map) (Advisory)

Organochlorine pesticides, PCBs
2005 Houston Ship Channel, Upper Galveston Bay

Spotted seatrout     

(Map) (Advisory)

PCBs
 2008
Galveston Bay

Spotted seatrout and all catfish species

(Map) (Advisory)

PCBs, dioxins/furans

2009

Clear Creek

All species of fish

(Map) (Advisory)

PCBs

 

Shellfish Harvest Areas

The consumption of oysters, especially raw, can pose a significant health risk because oysters can concentrate bacterial and viral pathogens in their tissues. The TDSHS Seafood Safety Division is responsible for regulating the harvest of oysters to protect the public from this health risk. Alternatively, the TCEQ is responsible for regulating water quality in areas designated for shellfish harvest via the Texas Surface Water Quality Standards. Harvest areas are classified by TDSHS based on the observed concentrations of fecal coliform bacteria in the water around the oyster reef. Oyster reefs can be closed on an emergency basis when pathogens or other harmful agents are detected in the water or in the oyster tissue. This type of closure occurred in summer 2000 due to red tide toxins in the oysters and in summer 1998 due to Vibrio parahaemolyticus infections in consumers. More recent closures have been due to large inflows of flood waters containing pollutants. For example, oyster harvesting was closed after Hurricane Ike caused oil and chemical spills and pushed large amounts of debris into the bay.

Maps are periodically produced by the TDSHS as a regulatory tool to designate shellfish harvest area classification in Texas bays. Harvest areas are classified as Approved, Conditionally Approved, Restricted or Prohibited. All shellfish harvested in Texas waters must come from approved or conditionally approved areas. Conditionally approved areas remain subject to classification changes based upon meteorological conditions that influence runoff. Oysters may be transplanted to private leases from restricted areas and harvested after a specified depuration period. Shellfish harvest area maps published by the TDSHS in 2003 and 2008 have been analyzed for spatial changes in the four classifications as shown in the figure to the right. The classifications of most potential shellfish harvest areas have remained the same.

Harvesting oysters is prohibited in areas of Galveston Bay that typically lie near the developed shore. Areas in which oyster harvest is approved tend to be closer to the Gulf, away from human development. Restricted and conditionally approved areas usually occur at the boundaries between the other two types and are likely to move in response to the amount of bacterial loadings from storm water run-off.

 

 

Related Pages:

Pathogens
Toxics
Oysters

 

MANAGEMENT SYSTEMS ARE IN PLACE TO PREVENT HARVEST AND SALE OF OYSTERS CONTAMINATED BY HUMAN DERIVED PATHOGENS. IMAGE ©ISTOCKPHOTO.COM/J. GANSER.
Management systems are in place to prevent harvest and sale of oysters contaminated by pathogens.   Image copyright istockphoto.com/J. Ganser.

 

 

 

 

 

 

Seafood Consumption Advisories
CURRENT SEAFOOD CONSUMPTION ADVISORIES IN GALVESTON BAY. DATA SOURCE: TDSHS.
Current seafood consumption advisories in Galveston Bay. Data Source: DSHS

 

 

 

 

 

 

 

 

 

TDSHS Harvest Area Maps
Texas Department of State Health Services Logo

 

 

 

 

 

 

 

 

 

Changes to Shellfish Harvest Areas
CHANGE IN SHELLFISH HARVEST CLASSIFICATION AREAS; 2003 VERSUS 2008. DATA SOURCE: (TDSHS 2003; TDSHS 2008D).
Change in shellfish harvest classification areas; 2003 versus 2008. Data Source: DSHS

 

 
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