Nutritional content, mercury, and trace element analyses of two skate (Rajidae) species in the Gulf of Alaska

Seafood is recognized as an important source of proteins and long chain omega-3 fatty acids. However, one of the primary concerns with seafood consumption is the level of heavy metals, particularly mercury, present in fish tissues, which may influence the demand of certain fishery products. We sampled muscle and liver tissues from 20 big (Beringraja binoculata) and 20 longnose (Raja rhina) skates collected near Kodiak and Cordova, Alaska, and analyzed their nutritional content (protein, moisture and lipid content and fatty acid profiles), heavy metal (mercury, arsenic, cadmium, lead) and trace element (selenium) load. Big and longnose skate muscle was composed of lean protein (14.7% ± 0.7% SD) with 1.2% (±0.4%) lipids and 83% (±0.8%) moisture. Skate livers were very high in lipids, between 52.5 and 57.5% and had high percentages of omega-3 fatty acids (30.2%). Mercury in these skates had mean levels of 0.21 mg/kg, lower than average levels found in Pacific halibut (Hippoglossus stenolepis). Overall, the risk/benefit ratio of consuming skate muscle was slightly positive (3.62%) based on the balance of mercury toxicity and omega-3 fatty acid benefits. Big skates were overall more beneficial to consume, and only longnose skates from Cordova had a negative risk/benefit ratio. These data can be used by the fishing industry to understand current and future market demands for skate products, and to be aware of any health concerns of consuming Gulf of Alaska skates.