An alien fisher in Patagonian South America

Abstract

While doing fieldwork in the Cape Horn Biosphere Reserve at the southernmost tip of South America (Patagonia), we saw an American mink (Neovison vison) diving into a kelp forest and later emerging with an enormous golden kingklip (Genypterus blacodes), which it ate on the rocky shore. Mink were introduced to Chile and Argentina by fur farmers in the 1940s. Since then, this invasive, semiaquatic mammal has spread through Patagonia, feeding on mammals, birds, and fishes. Of the fishes, mink prey on small exotic salmonids, galaxiids, and notothenioids. Astonishingly, this mink had caught a demersal fish that was larger than itself. The kingklip, a marine predator that is important for small-scale fisheries, inhabits depths from the intertidal zone to 1000 m, but is most abundant between 50 m and 500 m. So, this was likely an unusual prey for a mink, raising new questions about mink's feeding habits. Are we detecting all native species that are affected by invasive mink? Despite using scat or stable isotope analyses to identify the prey items of invasive species, direct observations can also contribute essential data. The kingklip has very small, smooth-edged scales, which can make it undetectable in scat. How did the mink catch a marine demersal fish? The boulder-covered seafloor is a perfect habitat for a kingklip, but mink must dive to catch this prey. Most diving mink studies are done in freshwater environments where dives typically do not exceed 3 m depth. Our observation also provides questions about invasive mink ecology: has their diving behavior been learned in marine environments, and are mink expanding beyond their normal range in this novel environment? What are the likely consequences for the marine food web in Patagonia?