Collection and Examination of Small-Bodied, Freshwater Fish for Helminth Parasites

Small-bodied, freshwater fish are often used in parasitological studies because they host a variety of parasites. As a result, it is important to have an accessible resource for the collection, housing, and examination of helminth parasites. Fish may be collected using passive (e.g., minnow traps or fyke nets) or active (e.g., seine netting or electrofishing) sampling methods depending on the species and water body being sampled. It is best to keep fish alive (e.g., in aquaria) until immediately prior to euthanasia for dissection. Using an overdose of anesthetic is the preferred method of sacrificing hosts as it limits distress and tissue damage. During dissections, the host should be separated into sections, e.g., the head, eviscerated body, and internal organs, to ensure accurate accounting of infection sites. If monogeneans are of interest the body surface and gills should be thoroughly examined. Natural history collections are also a source of small-bodied fish hosts that can be used to describe historical host-parasite interactions and changes in parasite communities. However, using natural history collections presents issues that require careful consideration, including what specimens are available, where the specimens are housed, obtaining permission from curators, and performing examinations on preserved specimens. Providing an easily accessible resource for recovering helminth parasites from small-bodied fish will allow researchers without backgrounds in parasitology to undertake quality parasitological studies.