Cyanotoxins accumulate in Lake St. Clair fish yet their fillets are safe to eat

Abstract

Consuming fish exposed to harmful algal blooms (HABs) may be a major route of microcystin toxin exposure to humans. However, it remains unknown whether fish can accumulate and retain microcystins during pre- and post-HAB periods when fishing is active, raising uncertainties about fish catch in waterbodies with recurring seasonal HABs. We conducted a field study on Largemouth Bass (Micropterus salmoides), Northern Pike (Esox lucius), Smallmouth Bass (Micropterus dolomieu), Rock Bass (Ambloplites rupestris), Walleye (Sander vitreus), White Bass (Morone chrysops), and Yellow Perch (Perca flavescens) to assess the true human health risks to microcystin toxicity via fish consumption. We collected 124 total fish in 2016 and 2018 from Lake St. Clair, a large freshwater ecosystem in the North American Great Lakes that is actively fished and regularly experiences HABs. Muscles were analyzed using the MMPB Lemieux Oxidation method for total microcystins, which was used to perform a human health risk assessment for comparison against fish consumption advisory benchmarks available for Lake St. Clair. From this collection 35 fish livers were additionally extracted to confirm the presence of microcystins. Although microcystins were detected in all livers at widely varying concentrations (1-1,500 ng g-1 wet weight (ww)), muscle levels were consistently low (0-15 ng g-1 ww). Following the fish consumption advisories for microcystins in Lake St. Clair, our results suggest that fish filets may be safely consumed during pre- and post-HAB periods.