OH seafood relatively safe amid rising tuna mercury levels

By Terri Dee

The Ohio Department of Health promotes the benefits of incorporating fish into a balanced diet as a low-fat food rich in healthy omega-3 fatty acids. But climate change is warming the world's oceans at an accelerated rate, and scientists predict the temperature change will push some fish species, particularly tuna, away from Pacific Island nations and toward the high seas. Tuna migrates to areas with ideal water temperatures for reproduction and food abundance.

Kevin McKay, CEO of Safe Catch Tuna, said multiple studies show warming ocean temperatures also affect how tuna grows.

"Fish use oxygen in order to produce the energy to grow," he explained. "The increase in the ocean temperature is decreasing the oxygen in the waters. This is causing fish to become smaller – they're maturing earlier and not getting to the same sizes that they were before."

McKay described how low oxygen levels inhibit a tuna's ability to maintain its energy for migration. Another effect is that tuna are eating more bait to survive, which creates an increase in the bioaccumulation of mercury. Research site DataOhio lists 47 fishing lakes statewide.

Tuna consumers may have concerns about the best and healthiest type of seafood to eat. Skipjack and yellowfin tuna have less mercury than albacore tuna, a larger fish that generally lives longer. McKay said even considering the effects of climate change, shoppers should not see a noticeable cost difference between tuna products.

"It is gonna affect it a little bit, because the fish are maturing earlier," he continued. "They're not getting to the same sizes. You're not going to get as much tuna per fish to go into the can. So it'll increase the raw material cost a little bit, but it's not going to have a huge effect on price."

Seafood industry research group Sustainable Fisheries UW says more than two billion people rely on seafood as their primary source of protein, and it's one of the least environmentally impactful proteins. The organization says it is a good idea to look for MSC-certified tuna caught in the USA, and for sourcing or fishing method information on the package.