Species Spotlight on Elephantear Mussel
By Cassie Hauswald
Freshwater mussels tend to have colorful names, which I like to imagine harkens back to a past when mussels were abundant enough to have localized names, such as the hickory nut, pigtoe, snuffbox and fawns foot to name a few. The elephantear has an equally charming, but not as imaginative a name since this particular mussel does closely resemble the ear of an African elephant in shape and color. On average the elephantear reaches 6 inches in length and is considered one of the largest freshwater mussels. In Blue River specimens average 5 inches in shell length. It is considered a big river species so its abundance in Blue River is especially interesting. In its lower reaches, Blue River has a mixture of large and medium river species co-existing, which makes the river’s mussel assemblage rather unique. The Ohio River’s influence is felt in Blue River’s as far north as Milltown.
The elephantear mussel ranked 6th in overall abundance in a 2003 mussel survey of the entire river. However, the fate of the mussel in Blue River is not as rosy at the numbers appear because no juveniles mussels of the species were found. In fact, the youngest individual was approximately 20 year of age, which means that since 1985 not much reproduction has occurred for this mussel in Blue River. Though Blue River may offer suitable habitat as evidenced by other successful mussel populations, the breakdown for this species may be in their larval host.
While many mussels are obligate parasites on a variety of fish species during their larval development, elephantears are only known to use one fish, the skipjack herring. Skipjack migrate upriver in the early spring to complete their spawning. Dams along large rivers hinder that progress so that only major flood events re-distribute the skipjack. Limitations on the mobility of skipjack herring are possibly limiting the reproductive success of elephantears since the mussels may release their larvae when there are little to no fish hosts present to parasitize. As the overall Ohio River population of elephantears increases in age so does that of the Blue River. The elephantear is listed as secure in Indiana according to NatureServe, but is a species that should be monitored. Its intriguing name and equally fascinating lifecycle add yet another facet to Blue River’s natural history mosaic.
More Results for the 2003 Mussel Survey
- 55.5 hours spent sampling the river
- 18 live species documented
- 74 sites sampled
- 933 specimens counted
- Purple wartyback (Cyclonaias tuberculata) was the most abundant species
- 4 species recorded in Salem Fork
- 5 species recorded in South Fork
Nature picture credits (top to bottom, left to right): Photo © K.S. Cummings/Illinois Natural History Survey(elephantear mussel) Photo © The Nature Conservancy (group of various freshwater mussels found in the Blue River).
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