Hidden Threat

There is more than one good reason to leave those big breeder size red drum in the water.

Story by Dr. Kesley Banks

Caught all year-round, red drum is an anglers favorite to note only catch but to serve on the dinner table. The most well-known way to prepare red drum is blackened, which was made famous by the late Chef Paul Prudhomme, owner of K-Paul’s Louisiana Kitchen in the French Quarter of New Orleans. This iconic recipe was introduced in the 1980s and resulted in a dramatic increase in the commercial harvest of red drum. By 1986, populations had been depleted so much that red drum were classified as overfished, sparking the closure of federal waters to recreational and commercial fishing for red drum that remain in effect today.

Red drum are an estuarine-dependent species early in its life. After reaching maturity, larger, older fish migrate offshore to spawn in the fall and remain there for the remainder of their 50-year life spans. This migration is often referred to as the “bull run.” These large, spawning fish, or bull reds, form large aggregations near bay and Gulf passes during this time making them easy to target and vulnerable to fishing. The harvest moratorium on the big breeder fish in federal waters has been key allowing the stocks to recover.

Fish like red drum play an important role in a healthy diet, whether you purchase your fish from the market or catch it yourself. While most fish are considered safe to eat, some have varying levels of contaminants like mercury, especially larger older individuals. Anglers often have questions regarding where these contaminants come from and how safe is it to eat your catch.

Mercury in the Environment

Contaminants are found throughout our environment, in the water, sediment, and even the air. Some are introduced by humans, through pollution, while other contaminants occur naturally in the environment. One of the most harmful contaminants is mercury, which is extremely poisonous and is found both naturally in the environment and as a pollutant. Mercury can enter the body through touch, inhalation, or consumption and causes severe health concerns.

Methylmercury is the most common form of mercury found in fish tissue and accumulates in higher concentrations as you move up the food chain. Benthic invertebrates and plankton absorb it through the sediment and water. These organisms are then eaten by small fishes, which are then eaten by larger predatory fishes. Some larger fish accumulate the methylmercury from their prey, which essentially means that the older and larger the fish, the greater the potential for high mercury levels in their bodies. These larger fish are then caught and eaten by us, causing the methylmercury to accumulate in our tissues, which can then lead to varying degrees of mercury poisoning.

Originally discovered in 1956 in Minamata Bay, Japan, locals experienced tingling in their hands and feet, reduced motor control, tremors, speech impairment, and mental retardation after consuming mercury contaminated seafood. The resulting illness was named Minamata disease and was caused by the discharge of industrial wastewater that contained mercury in the Minamata Bay.

So How Safe is it to Eat Your Catch?

Fish consumption advisories for specific waterbodies or susceptible groups of the population are put in place by local, state, and national agencies. Mercury accumulation in fishes in the Gulf of Mexico has been well established, even in red drum. Because they are long lived, grow to a large size, and forage relatively high in the food chain, red drum are prone to bioaccumulation of mercury and other toxins. The United States Food and Drug Administration (FDA), which oversees commercial fisheries, issues advisories when mercury concentrations are higher than 1.0 ppm wet weight, while the Environmental Protection Agency (EPA) issues recommendations for recreational fisheries if mercury concentrations are higher than 0.3 ppm wet weight. States are tasked with setting advisories within their borders for waterbodies found to have fish with elevated mercury levels.

Studies have shown that larger red drum can have elevated mercury concentrations above the acceptable limits. Fortunately, those studies also showed red drum within slot sizes are generally below the advisory limits and safe to eat unless an advisory is set for a particular waterbody. The prohibited retention of red drum in federal waters no only helps conserve the spawning stock but limits the amount of large red drum loaded with mercury being consumed by anglers. Unfortunately, the prohibition on commercial harvest of red drum in the future is not completely certain.

“Occasionally there are misguided efforts to reopen harvest of big breeder-sized red drum at the Gulf of Mexico Fishery Management Council, which would jeopardize not only the health of the fishery, but the health of consumers who have no idea of the hidden toxicity of those big fish,” said Ted Venker, Conservation Director for CCA National. “The Science is clear – retain red drum within the slot size for consumption and practice catch and release for oversized fish.”

Kesley Banks, Ph.D. is a Postdoctoral Assistant Research Scientist in the Center for Sportfish Science and Conservation at the Harte Research Institute for Gulf of Mexico Studies (HRI) at Texas A&M University-Corpus Christi. She graduated from Texas A&M University – Corpus Christi in December 2019 with a doctorate in marine biology and was one of the first recipients of a Science of Conservation Marine Scholarship. The Science of Conservation Scholarship program was founded in 2018 through a partnership of Shimano and CCA and is dedicated to benefitting students furthering their marine science education.

Kevin Hickson

Author Kevin Hickson

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