Opening a can of worms: Archived canned fish fillets reveal 40 years of change in parasite burden for four Alaskan salmon species

Abstract

How has parasitism changed for Alaskan salmon over the past several decades?Parasitological assessments of salmon are inconsistent across time, and thoughparasite data are sometimes noted when processing fillets for the market, thosedata are not retained for more than a few years. The landscape of parasite riskis changing for salmon, and long-term data are needed to quantify this change.Parasitic nematodes of the family Anisakidae (anisakids) use salmonid fishes asintermediate or paratenic hosts in life cycles that terminate in marine mammaldefinitive hosts. Alaskan marine mammals have been protected since the 1970s,and as populations recover, the density of definitive hosts in this region has in-creased. To assess whether the anisakid burden has changed in salmonids overtime, we used a novel data source: salmon that were caught, canned, and ther-mally processed for human consumption in Alaska, USA. We examined canned fil-lets of chum (Oncorhynchus keta, n = 42), coho (Oncorhynchus kisutch, n = 22), pink(Oncorhynchus gorbuscha, n = 62), and sockeye salmon (Oncorhynchus nerka, n = 52)processed between 1979 and 2019. We dissected each fillet and quantified thenumber of worms per gram of salmon tissue. Anisakid burden increased over timein chum and pink salmon, but there was no change in sockeye or coho salmon. Thisdifference may be due to differences in the prey preferences of each species, or todifferences in the parasite species detected across hosts. Canned fish serve as awindow into the past, providing information that would otherwise be lost, includinginformation on changes over time in the parasite burden of commercially, culturally,and ecologically important fish species