The occurrence of paralytic shellfish toxins in invertebrates, forage fishes and predatory fishes across southern Alaska.

In Alaska, paralytic shellfish poisoning (PSP) is associated with the toxic dinoflagellate Alexandrium catenella, which blooms annually along the coastline from the Canadian border to the Beaufort Sea. While it has long been recognized that these blooms cause annual outbreaks of shellfish toxicity each spring and summer, little is known about other pathways for PSP toxins in the marine food web. Here, we present data from a four-year study to characterize the occurrence of PSTs in marine non-bivalve invertebrates, forage fishes and predatory fishes across the breadth of southern Alaska. Samples were obtained at coastal sites throughout the Gulf of Alaska, including the Aleutian Islands, Alaska Peninsula, Cook Inlet region, Prince William Sound and southeast Alaska, as well as sites in the southeastern Bering Sea. Collectively, 235 non-bivalve invertebrate samples, 1511 forage fish samples and 364 commercially important predatory fish were collected and analyzed for PSP toxins (PSTs) via an improved ELISA method. Overall, 41% of specimens exhibited detectable levels of PSTs across 14 invertebrate taxa, 23 forage fish species and 7 species of predatory fishes. In non-bivalve invertebrates, 39.8% of samples were positive for PSTs with the greatest levels in crabs, sea stars and carnivorous snails. In forage fishes, >35% showed detectable PST levels, with the highest in Pacific Sand Lance, Pacific Herring, juvenile Pacific Cod, juvenile Pacific Tomcod, Capelin, Surf Smelt and juvenile salmon. Notably, toxins were commonly present in important prey for seabirds and marine mammals, in addition to juveniles of commercially important fishes. In predatory fishes, PSTs were detected in 60-75% of all tissues tested, with the highest incidence in fish liver and kidney tissue, and lowest in stomach contents. PST levels were low in muscle tissue, signifying low toxicity risks to humans consuming filets. However, the prevalence of these toxins in so many fishes suggests potential impacts to survival and recruitment of juvenile predatory fishes in Alaskan coastal areas.