Fish behavioral response to lures produced by the plain pocketbook mussel (Lampsilis cardium)

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Leonard Steinert and Todd D. Levine, Biology, Carroll University, Waukesha, WI

Background/Question/Methods
Mussels species belonging to the Unionidae family are among the most threatened group of animals in North America, and part of the reason for this may be in part due to their complex life cycle. Many species in this family use lures to attract host fish for their glochia. Lampsilis cardium is one of the species that uses a modified piece of mantle tissue to lure and attract host fish. Although laboratory tests identify which fish are capable of hosting mussels, lab tests cannot determine which fish will interact with the mussel lures in their habitat. Fish species that are important to maintaining wild populations of mussels depends on both the physiology understood through laboratory tests and the way that fishes respond to mussel lures in their natural environment. Fish species that are physiologically suitable for parasitic glochidia must bite or strike the lure of a gravid female L. cardium in order for successful maturation of larvae. We conducted approximately 1 hour observations by using remote cameras to record fish behavior near L. cardium displaying their lures, mussels without lures and in areas of the river without mussels.
Results/Conclusions
While a large number of fishes have been observed in the river (roughly 50 species), only a few were observed in our videos of displaying L. cardium. Five of those species exhibited interest in mussels, reflected by time spent near and oriented toward the mussels. Fundulus notatus, Lepomis macrochirus, and Lepomis gibbosus were observed striking the active lure of a displaying mussel. We compared the fish activity to laboratory reports of host suitability. At least the two sunfish were physiologically compatible with the mussels that we observed. From preliminary results, several fish may be potential hosts both physiologically and behaviorally. The diversity of fish species available to populations of L. cardium are slightly different from river to river, and different populations of mussel might use fish communities slightly differently. In depth understanding of this critical life stage of Unionidae mussels is necessary for effective conservation efforts.