Shawnee Twin Lakes was one of seven Oklahoma lakes that have been added to the Oklahoma Department of Environmental Quality (DEQ) list of lakes with consumption advisories for mercury that was released on Thursday, August 19. Other lakes added were Chandler Lake, Lake Hefner, Sooner Lake, Lake Tenkiller, Lake Texoma, and Lake Thunderbird. According to the DEQ, the levels of mercury in a lake do not affect the lake’s safety as a source of drinking water or for lake recreation such as swimming and boating.

Five other lakes were removed from the list since recommendations were last made in early 2020.

When bigger fish eat smaller ones, the predators also absorb their prey’s contamination in a process known as biomagnification. This is why smaller fish are generally safer to eat than large fish. EPA began a cooperative effort in 1995 to assemble a nationwide data base on total mercury concentrations in fish tissue. The first objective of this project was to assemble and review data on the mercury contamination in fish tissue. This step included identifying appropriate state, such as Oklahoma DE, and federal agencies and other groups with relevant data on mercury concentrations in fish. The second step in this project involved the development of a fish tissue data base, organizing relevant data to be used for future analyses.

EPA restrictions divide the population into two groups: general population and sensitive population. The general population includes males age 15 and older and women past childbearing age. The sensitive population includes women of childbearing age, pregnant or nursing mothers, and children under age 15.

The EPA scale for fish tissue concentrations (mg/kg) is: less than 0.5 - no restrictions; 0.5 – 1.0 – 2 meals per month for sensitive and no restrictions for general; 1.0 – 1.5 – no consumption for sensitive and 2 meals per month for general; over 1.5 – no consumption for either group.

Recommendations for SHAWNEE TWIN LAKES: Flathead Catfish; Sensitive - no restrictions on fish under 22 inches, two meals per month for fish 22 – 27 inches, and no meals per month for fish 37 inches and over. General - no restrictions on fish under 37 inches and two meals a month on fish 37 inches and over. Largemouth Bass: Sensitive – no restrictions under 17 inches, two meals per month 17 inches and over. General - no restriction. Saugeye; Sensitive – no restrictions under 22 inches, two meals per month 22 inches and over. General – no restriction. Spotted Bass; Sensitive – no restrictions under 16 inches, two meals a month 16 inches and over. General – no restriction.

There are no restrictions on Channel Catfish, White Bass, or White Crappie.

The following recommendations for area lakes were issued previously by the DEQ.

Recommendations for SPORTSMAN LAKE: Channel Catfish; Sensitive - no restrictions under 20 inches, two meals per month 20 inches and over. General – no restrictions

Largemouth Bass; Sensitive – no restriction under 16 inches, two meals per month 15 – 20 inches, no meals per month 20 inches and over. General – no restrictions under 20 inches, two meals per month 20 inches and over. Spotted Bass; Sensitive – no restrictions under 15 inches, two meals per month 15 – 17 inches, no meals per month 17 inches and over. General – no restrictions under 17 inches, two meals per month 17 inches and over.

No other fish were samples at this lake.

WEWOKA LAKE: Blue Catfish; Sensitive – no restrictions under 23 inches, two meals per month 23 inches and over. General – no restrictions. Flathead Catfish; Sensitive – no restrictions under 21 inches, two meals per month 21 -29 inches, no meals per month 29 inches and over. General – no restrictions under 29 inches, two meals per month 29 inches and over. Largemouth Bass; Sensitive – no restrictions under 17 inches, two meals per month 17 inches and over. General – no restriction. Saugeye; Sensitive - no restriction under 21 inches, two meals per month 21 inches and over, General – no restriction. Spotted Bass; Sensitive – no restriction under 14 inches, two meals per month 14 inches and over. General – no restriction. Channel Cat – no restrictions

KONAWA LAKE; tested and no restrictions.

HOLDENVILLE LAKE; Blue Catfish; Sensitive – two meals per month all lengths. General – no restrictions. Channel Catfish; Sensitive – no restrictions under 21 inches, two meals per month 21 inches and over. General – no restrictions. Flathead Catfish; Sensitive – no restrictions under 26 inches, two meals per month 26 inchers and over. General – no restrictions. Largemouth Bass; Sensitive – no restrictions under 17 inches, two meals per month 17 inches and over. General – no restrictions. Spotted Bass; Sensitive – no restrictions under 15 inches, two meals per month 15 inches and over. General – no restrictions. White Crappie; no restrictions.

A complete list of recommendations for Oklahoma lakes can be found at the https://go.usa.gov/xFfc9 website.