Evidence for the decline and possible extinction of a marine parasite species caused by intensive fishing

Abstract

Abstract The first good evidence of the role of intensive commercial fishing in the decline and possible extinction of a marine parasite is presented. The larva of Stichocotyle nephropis Cunningham, 1887 (Aspidogastrea: Digenea) was described in 1887 from the outside of the intestine of the decapod crustacean Nephrops norvegicus (L., 1758) in the North Sea. Similar larvae were found outside the intestine of the American lobster Homarus americanus (Milne-Edwards, 1837) caught off New England in 1895. The adult form was first found in 1898 in the bile ducts of the thornback ray Raja clavata (L., 1758) from the North Sea, then in the barndoor skate Dipturus laevis (Mitchill, 1818) caught off Nantucket. There have been few records of its occurrence since then, with the last records from the northeast and northwest Atlantic published in 1972 and 1986 respectively, despite the recent attempts reported herein to find larvae and adult parasites. Both the elasmobranch final hosts are listed as “near threatened” or “ endangered” and the latest evidence on their population sizes suggests that they may have been fished to below the thresholds required for successful transmission of the parasite.