Controlling Proteocephalus ambloplites (Cestoda) Infections and Changing Fish Parasitic Fauna Following Post-Rotenone Rehabilitation of Lakes, With Light Microscopy

Abstract

Efforts to establish desirable fish populations by rotenone treatment of lakes dominated by winter-kill resistant species, e.g., bullhead, and restocking have been attempted by the Wisconsin Department of Natural Resources, as well as by other agencies throughout the United States since the mid-1930s. Such efforts were performed in Little Elkhart Lake, eastern Wisconsin which was treated with rotenone (1.5 ppm) in 1981, to kill its rough fish and restock with desirable fish populations. Pre- and posttreatment samples of fish were examined for parasites in September 1981 and 1988, respectively. This is a revision and update of work originally published in 1993 with the addition of light microscope images of recovered parasites for the first time. Relatively heavy infections in largemouth bass, Micropterus salmoides, (Lacépède) and sunfish in 1981 with Proteocephalus ambloplites (Leidy, 1887) (Cestoda) disappeared after the rotenone treatment. Infections with Neoechinorhynchus cylindratus Van Cleave, 1913 decreased but drastically increased with Leptorhynchoides thecatus (Linton, 1891) Kostylew, 1924 with changes in their fish and invertebrate host populations following rotenone use. Metacercariae of Posthodiplostomum minimum (MacCallum, 1921) (Trematoda) in sunfish and Hysterothylacium brachyurum Ward and Magath, 1917 (Nematoda) in largemouth bass were also present before and after the chemical treatment, respectively. The observed loss of P. ambloplites after 1981 points to a possible method for its control. The unusual presence of the leech Myzobdella lugubris in the anterior intestine of a yellow perch, Perca flavescens (Mitchill) was documented.