A recent pilot study of contaminants in black drum, spotted seatrout and redfi sh indicates a need for further
study after six large redfish from a test of about 50 revealed high levels of heavy metals and other substances.
In a project funded by the Coastal Bend Bays & Estuaries Program, Greg Stunz, professor of marine biology, and the endowed chair for fisheries and ocean health at the Harte Research Institute for Gulf of Mexico Studies, and his research crew caught and had analyzed 49 fish during the 2010 summer for mercury, polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenxofurans (PCDFs).
In July 2008, the Texas Department of State Health Services (TDSHS) posted consumption advisories for
spotted seatrout and all catfi sh species in the Galveston Bay area due to elevated contaminant levels.
“My phone started ringing with lots of concerned anglers here,” said Stunz.
“We were wondering if there was concern in our area, but there wasn’t really any recent data.”
CBBEP project manager Jace Tunnell consulted with the TDSHS in the design of a small pilot study to determine if there was a need for additional research. And there is, Stunz said.
“The good news is contamination is relatively low in most species, but it was higher in some species, particularly bull redfish,” he said.
They caught a total of 49 fish from Nueces Bay, Corpus Christi Bay, Aransas Bay, the Upper Laguna Madre, Baffin Bay, and on the Gulf beach around Port Aransas. The researchers followed a careful procedure for collecting and shipping the fish tissue for lab analysis. All were tested for mercury and 36 were tested for PCBs and PCDDs/PCDFs.
Most of the fish had very low, often undetectable levels for contaminants studied.
But one redfish measuring around 36 inches in length from Corpus Christi Bay tested 50 times higher than the
Texas Department of State and Health Services recommended consumption level for PCBs.
The lab repeated the test three times on the sample to ensure accuracy, and all tests were similar.
This redfish was estimated at seven years old. With a lifespan of 50 years, the fish could continue to accumulate
toxins for many years.
The study also showed higher-than-acceptable levels of mercury in four of the five oversize redfish (sizes ranging from 32 to 40 inches) collected from the surf zone. For those fish, the larger they were, the higher their mercury levels. The mean age for the five redfish caught in the surf zone was 20 years old. Four of the five redfish caught in the surf zone were above the acceptable TDSHS mercury level for consumption. Only mercury tests were completed for the surf zone redfish so other contaminants are an unknown for these five oversize redfish.
Spotted seatrout and black drum analyzed had very low levels of all contaminants and the researchers recommend no additional study for these species.
Results of this study are currently under review by the TDSHS, which handles consumption advisories. Another important point to make about all of the fish species collected during this study are that they move in and out of the bays and up and down the coast. So just because a fish is caught in a certain bay, doesn’t necessarily mean that the fish has lived in that bay its entire life. This is important to note when trying to discern where and how contamination of a fish has occurred over time.
Mercury finds its way into water mostly through emmissions of burning coal for energy. In humans, mercury can harm the central nervous system and is known to cause problems in the development of organs and nerves in developing fetuses.
PCBs were used as coolants and insulating fluids in electrical equipment and for other industrial uses. PCBs affect the cardiovascular system, liver and skin and are considered probable carcinogens.
PCDDs/PCDFs are produced through metal smelting, refining and chemical manufacturing. PCDDs/PCDFs are released into the atmosphere and enter the food chain.
While no conclusion can be made with only six fish testing high, researchers recommend further study on large oversize redfish. Redfish are popular to catch, and a favorite meal, too. Fishermen are only allowed to keep two
redfish larger than 28 inches a year, but those fish yield many pounds of meat, so it’s important to consider if any additional advisories or restrictions are needed.
Stunz said the level of contamination is discouraging. “Future research looking at these oversize red drum
would be important.”
For additional information about the Coastal Bend Bays & Estuaries Program, contact Beth Wilson, communications manager, at (361) 885-6246 or bwilson@cbbep.org.
Download the .pdf project flyer here.