Lampsilis higginsii - (I. Lea, 1857)
Higgins Eye
Synonym(s): Lampsilis higginsi (I. Lea, 1857)
Taxonomic Status: Accepted
Related ITIS Name(s): Lampsilis higginsii (I. Lea, 1857) (TSN 80018)
Unique Identifier: ELEMENT_GLOBAL.2.112888
Element Code: IMBIV21100
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
 
Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Lampsilis
Genus Size: D - Medium to large genus (21+ species)
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Concept Reference
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Concept Reference: Turgeon, D.D., J.F. Quinn, Jr., A.E. Bogan, E.V. Coan, F.G. Hochberg, W.G. Lyons, P.M. Mikkelsen, R.J. Neves, C.F.E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F.G. Thompson, M. Vecchione, and J.D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland: 526 pp.
Concept Reference Code: B98TUR01EHUS
Name Used in Concept Reference: Lampsilis higginsii
Conservation Status
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NatureServe Status

Global Status: G1G2
Global Status Last Reviewed: 25Jun2010
Global Status Last Changed: 30Mar1994
Rounded Global Status: G1 - Critically Imperiled
Reasons: Although never a common species, range has been reduced to a few remaining sites on the Mississippi River (a decline of over 50% recently and likely over 80% historically) and two tributaries (from 9 historically). Recent reintroduction and new populations have been discovered but zebra mussels (not a threat during initial conservation assessment of 1982) now pose a serious threat to many of the most viable populations and predictive models indicate futher decline, although some evidence of recovery in the presence of zebra mussels has been shown.
Nation: United States
National Status: N1N2 (25Jun2010)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Illinois (S1), Iowa (S1), Minnesota (S1), Missouri (S1), Nebraska (S1), South Dakota (S1), Wisconsin (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (14Jun1976)
U.S. Fish & Wildlife Service Lead Region: R3 - North Central
IUCN Red List Category: EN - Endangered
Convention on International Trade in Endangered Species Protection Status (CITES): Appendix I
American Fisheries Society Status: Endangered (01Jan1993)

NatureServe Global Conservation Status Factors

Range Extent: 1000-5000 square km (about 400-2000 square miles)
Range Extent Comments: The historic distribution before 1965 was given as the main stem of the Mississippi River from just north of St. Louis, Missouri, to just south of St. Paul, Minnesota; in the Illinois, Sangamon, and Rock Rivers in Illinois; in the Iowa, Cedar, and Wapsipinicon Rivers in Iowa; in the Wisconsin and St. Croix rivers in Wisconsin; and, in the Minnesota River in Minnesota (based on Havlik, 1980; USFWS, 1983). A questionable report of this species in the lower Ohio River was also given (Havlik, 1980). A study by Cawley (1996) extended the reported range of Lampsilis higginsii 98 miles to the south and 82 miles to the north based on the collection of dead specimens. As such, current distribution in the upper Mississippi River is between La Crosse, Wisconsin, and Muscatine, Iowa, as well as the St. Croix, and Wisconsin Rivers (Miller and Payne, 2007).

Area of Occupancy: 126-2,500 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: 6 - 20
Number of Occurrences Comments: This species is restricted to a few sites in the following drainages: Copperas-Duck, Flint-Henderson, Lower Rock, Grant-Little Maquoketa, Coon-Yellow, Lower Wapsipinicon, Lower St. Croix, Twin Cities, Rush-Vermillion, La-Crosse-Pine (see USFWS, 1982 and USFWS, 2004). The latest recovery plan lists 10 (up from 7 in previous plan) locations as primary habitats (6 in Mississippi River between river miles 489 and 656, 1 in Wisconsin River, 3 in St. Croix River) and 9 (same as previous plan) as potential secondary habitats, with reintroductions since 2000 into 4 rivers from which it had previously been extirpated (USFWS, 2004), including pool 4 and the Twin Cities region nof the Mississippi River below St. Anthony Falls, Minnesota (Sietman, 2003). Miller and Payne (2007) summarize the distribution following the latest recovery plan (USFWS, 2004) as: upper Mississippi River is between La Crosse, Wisconsin, and Muscatine, Iowa, as well as the St. Croix, and Wisconsin Rivers.

Population Size: 100,000 - 1,000,000 individuals
Population Size Comments: Mathiak (1979) reported collecting 45 specimens from the Mississippi River in Wisconsin in 1975 prior to the species' listing as an endangered species in 1976; mostly from a commercial clamming operation. Cawley (1996) noted that 510 specimens of Lampsilis higginsii had been collected since 1980. Hornbach et al. (1995) examined populations in the St. Croix River and estimated populations to be 4,000 mussels at Franconia, 4,000 to 10,000 mussels at Prescott, Minnesota, and 238,000 to 260,000 mussels at Hudson, Wisconsin (all listed as Essential Habitat Areas in the initial recovery plan). Heath (in litt. 1998), and Heath et al. (1999) collected almost 90 L. higginsii from 1987-1999 in the area of the St. Croix river, extending upstream of Franconia, MN to the Interstate Park Area (Taylor's Falls, MN) - about 3 river miles. They estimate L. higginsii population densities of approximately 0.01 individuals/m2. In 2000, mean density estimates of L. higginsii at Interstate Park and Hudson were 0.01 and 0.09, respectively (Heath et al., 2001); these estimates did not reflect a statistically significant change in abundance at either site. Estimates of population size were 9,224 (95% CI = 4,192 - 14,255) at Hudson and 4,212 (95% CI = 358 - 7,886). Hornbach et al. (1995) estimated that there were 4000 live individuals in the St. Croix River at RM 50.2 and as many as 260,000 at RM 17.6. In a recent re-evaluation of the species in the Upper Mississippi River (Miller and Payne, 2007), the number of L. higginsii at Essential Habitat Areas (EHAs) ranged from several thousand to more than 500,000. The species is much less abundant in the Wisconsin River and St. Croix River EHAs. In 2001 this species was found alive at four sites in the Upper Mississippi River National Wildlife and Fish Refuge (formerly Savanna Army Depot) in Illinois/Iowa between RM 544.5 and 558.4 in relative abundance from 0.9 to 2.6% (Sietman et al., 2004).

Number of Occurrences with Good Viability/Integrity: Very few (1-3)
Viability/Integrity Comments: Cawley (1996) noted that 510 specimens of Lampsilis higginsii had been collected since 1980. Thiel (1981) stated that Pool 10 of the Mississippi River supported the largest population of L. higginsii. The area in the East Channel of the Mississippi River, by Prairie du Chien, Wisconsin, was considered to be the most productive L. higginsii habitat in the Mississippi River system. Since Cawley's (1996) review, however, zebra mussels (Dreissena polymorpha) have drastically reduced the population of L. higginsii at Prairie du Chien. The first recovery plan (USFWS, 1983) included six locations in the Upper Mississippi River and one in the St. Croix River as essential habitats because they supported viable reproductive populations and the second recovery plan (USFWS, 2004) identified 3 more (1 in the Wisconsin River and 2 in the St. Croix River), identifying these regions as "Essential Habitat Areas (EHA).

Overall Threat Impact: High
Overall Threat Impact Comments: Fuller (1978) suggested that overfishing may be at least in part responsible for the decline of this species. Based on collecting efforts with a commercial clamming operation in Prairie du Chien, Wisconsin, Mathiak (1979) estimated that hundreds were harvested in the years prior to the species' listing as an endangered species in 1976, likely leading to its eventual listing as an endangered species. Although zebra mussels are currently the most important threat (in all areas) to Lampsilis higginsii, habitat alteration (construction activities, channelization, sedimentation, dredging), environmental contaminants (spills, seasonal runoff flushings, sediments, agricultural runoff), other invasive species (black carp, round goby, and poor water quality may also pose significant threats (USFWS, 2004). Commercial harvest has been identified as a small historical threat only. Both recovery plans (USFWS, 1983; 2004) suggest the reduced range of the species could be attributed to anthropogenic impacts: increased sedimentation, river modifications, and poor water quality; as well as impact from zebra mussels, although it does have some capability of recovering from such infestations. Historical data do not provide clear evidence that stable, recruiting populations ever existed in the 7 tributaries where it has not been collected recently (Miller and Payne, 2007).

Short-term Trend: Decline of 30-50%
Short-term Trend Comments: It has been eliminated from approximately 45% of its original range. Thiel (1987) reported mid-1980's die-offs of mussels in the Mississippi River that were most noticeable in areas of Lampsilis higginsii occurrence. Cummings and Mayer (1997) noted it is extirpated from all other (5 total) drainages where it was historically found in Illinois except a few sites on the Mississippi River. Blodgett and Sparks (1987) noted a decline in the unionid community near the Sylvan Slough Essential Habitat Area and Havlik (1987) noted a die-off near Prairie du Chien, Wisconsin, another Essential Habitat Area. Havlik (1987) also indicated an unusual number of fresh-dead Lampsilis higginsii at this site in 1985. Few papers presented at a workshop examining die-offs (Neves, 1987) gave concrete reasons for the cause of the die-off, however Scholla et al. (1987) indicated that a gram-negative rod bacterium, which forms yellow colonies was associated with sick mussels from the Tennessee River. Latest recovery plan lists 10 (up from 7 in previous plan) locations as primary habitats (6 in Mississippi River between river miles 489 and 656, 1 in Wisconsin River, 3 in St. Croix River) and 9 (same as previous plan) as potential secondary habitats, with reintroductions since 2000 into 4 rivers from which it had previously been extirpated (USFWS, 2004). Data from Miller and Payne (2007) suggest the species may not be in imminent danger of extinction, has always been rare, and is not adapted to small rivers.

Long-term Trend: Decline of 70-90%
Long-term Trend Comments: The Higgins eye pearlymussel was never abundant and Coker (1919) indicated that it was becoming increasingly rare even at the end of the 1800s. The fact that there were few records of live specimens from the early 1900s until the enactment of the Endangered Species Act in 1973 was a major factor in its listing in 1976; and historical and archaeological sites indicate the species has consistently been a rare component of the river fauna (Miller and Payne, 2007). Pre-1965 range was from Prescott, Wisconsin (RM 811) to Louisiana, Missouri (RM 283), a distance of 850 km (Havlik, 1981); as well as 9 tributaries (Minnesota River, Minnesota; St. Croix and Wisconsin Rivers, Wisconsin; Rock, Illinois, and Sangamon Rivers, Illinois; Wapsipinicon, Iowa, and Cedar Rivers, Iowa). After 1965, 196 and 248 km were lost from the northern and southern part of its range, respectively (overall decline of > 50%) and tributary occurrences declined from 9 to 2 (St. Croix and Wisconsin Rivers) (Havlik, 1981). Data from Miller and Payne (2007) suggest the species may not be in imminent danger of extinction, has always been rare, and is not adapted to small rivers.

Intrinsic Vulnerability: Highly vulnerable
Intrinsic Vulnerability Comments: This species was never abundant to begin with plus has experienced some decline (USFWS, 2004), however, it has been shown to be adapted as a rare species even historically and, despite some early occurrences in smaller tributaries, is a large-river species and recently has shown some potential for recovery even in the presence of zebra mussels (Miller and Payne, 2007).

Environmental Specificity: Very narrow. Specialist or community with key requirements scarce.
Environmental Specificity Comments: The species is restricted to high flow conditions only primarily in large rivers (difficult to survey) and early occurrences in slower flowing smaller tributaries was represented by very small populations with poor or no viability (Miller and Payne, 2007).

Other NatureServe Conservation Status Information

Inventory Needs: Develop interagency partnerships to conserve, monitor, and inventory populations; especially those with zebra mussels present.

Protection Needs: The removal of zebra mussels in a manner and scale necessary to benefit L. higginsii is evidently not currently feasible. Therefore, the plan focuses on developing methods to prevent new infestations, monitoring zebra mussels at Essential Habitat Areas, and developing and implementing contingency plans to alleviate impacts to infested populations. Based on recent activities, the latter may consist largely of removing L. higginsii from areas where zebra mussels pose an imminent risk to the persistence of the population and releasing them into suitable habitats within their historical range where zebra mussels are not an imminent threat. Because this is a species that is widespread but uncommon, it can be best protected by implementing conservation strategies that safeguard rich and diverse mussel assemblages and the habitats upon which they depend, as opposed to conservation at the species level (Miller and Payne, 2007).

Distribution
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Global Range: (1000-5000 square km (about 400-2000 square miles)) The historic distribution before 1965 was given as the main stem of the Mississippi River from just north of St. Louis, Missouri, to just south of St. Paul, Minnesota; in the Illinois, Sangamon, and Rock Rivers in Illinois; in the Iowa, Cedar, and Wapsipinicon Rivers in Iowa; in the Wisconsin and St. Croix rivers in Wisconsin; and, in the Minnesota River in Minnesota (based on Havlik, 1980; USFWS, 1983). A questionable report of this species in the lower Ohio River was also given (Havlik, 1980). A study by Cawley (1996) extended the reported range of Lampsilis higginsii 98 miles to the south and 82 miles to the north based on the collection of dead specimens. As such, current distribution in the upper Mississippi River is between La Crosse, Wisconsin, and Muscatine, Iowa, as well as the St. Croix, and Wisconsin Rivers (Miller and Payne, 2007).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: endemic to a single nation

U.S. & Canada State/Province Distribution
United States IA, IL, MN, MO, NE, SD, WI

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
IA Allamakee (19005), Clayton (19043), Clinton (19045), Des Moines (19057), Dubuque (19061), Jackson (19097), Johnson (19103), Lee (19111)*, Linn (19113), Louisa (19115), Lyon (19119), Muscatine (19139), Scott (19163)
IL Henderson (17071), Jo Daviess (17085), Mercer (17131)*, Rock Island (17161), Whiteside (17195)
MN Carver (27019), Chisago (27025), Dakota (27037), Goodhue (27049), Hennepin (27053), Houston (27055), Ramsey (27123), Scott (27139), Wabasha (27157), Washington (27163), Winona (27169)
MO Marion (29127)
NE Cuming (31039)*
SD Yankton (46135)
WI Buffalo (55011), Columbia (55021), Crawford (55023), Dane (55025), Grant (55043), Iowa (55049), La Crosse (55063), Pierce (55093), Polk (55095), Richland (55103), Sauk (55111), St. Croix (55109), Trempealeau (55121), Vernon (55123)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
07 Twin Cities (07010206)+, Lower Minnesota (07020012)+, Lower St. Croix (07030005)+, Rush-Vermillion (07040001)+, Cannon (07040002)+, Buffalo-Whitewater (07040003)+, La Crosse-Pine (07040006)+, Coon-Yellow (07060001)+, Grant-Little Maquoketa (07060003)+, Turkey (07060004)+, Apple-Plum (07060005)+, Lower Wisconsin (07070005)+, Copperas-Duck (07080101)+, Upper Wapsipinicon (07080102)+, Lower Wapsipinicon (07080103)+*, Flint-Henderson (07080104)+, Upper Cedar (07080201)*, Upper Iowa (07080207)*, Lower Iowa (07080209)+, Pecatonica (07090003)*, Lower Rock (07090005)+, Kishwaukee (07090006)*, Green (07090007)*, Bear-Wyaconda (07110001)*, The Sny (07110004)+, Kankakee (07120001)*, Iroquois (07120002)*, Lower Illinois-Lake Chautauqua (07130003)*, Spoon (07130005), Upper Sangamon (07130006)*, Lower Sangamon (07130008)*, Salt (07130009)*, Lower Illinois (07130011)*
10 Lewis and Clark Lake (10170101)+, Rock (10170204)+, Lower Elkhorn (10220003)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A freshwater mussel with a heavy yellow or brown shell often with green rays.
General Description: (From Parmalee 1967:67-68) "Shell oval, elliptical or rhomboid, somewhat inflated, thick heavy; anterior end rounded, posterior end bluntly pointed in the male, truncated in the female. Beaks directly forward, swollen, elevated; sculpture consists of a few, slightly looped feeble ridges. Posterior ridge rounded but distinct. Surface usually shiny marked by irregular growth lines which are more pronounced at rest periods where they become dark colored. Epidermis yellowish or olive, with faint to quite distinct green rays.

Left valve with two triangular or pyramidal, thick, erect, divergent, serrated pseudocardinal teeth; the two lateral teeth heavy, moderately thick and short, roughened. Right valve with a large, erect, massive, triangular tooth in front. Interdentum fairly narrow; beak cavity deep. Nacre silvery-white, often tinged with pink; iridescent posteriorly." See illustration in Parmalee (1967).

Diagnostic Characteristics: This species has been confused with Lampsilis abrupta from the Ohio River System. Higgin's eye has lower umbo and a lighter periostracum (Havlik, 1981). This species exhibits marked sexual dimorphism with the posterior end in the females sharply truncated with a post-basal swelling. The posterior end in the males is more roundly pointed. A number of species can be confused with L. higginsii. Those cited as most similar are Obovaria olivaria, L. cardium, L. siliquoidea, L. abrupt and Actinonaias ligamentina (Baker, 1928; Cummings and Mayer, 1992). Although nothing has been published specifically on the internal anatomy of L. higginsii, Baker (1928) indicates it is most likely similar to that of other lampsilines.
Reproduction Comments: The exact breeding season is unknown, but the closely related Lampsilis abrupta is gravid from September to June (Ortmann, 1919). Sexual maturity is reached in 6-12 years and an individual may live up to 50 years. From USFWS (2004): Early studies indicated that the sauger (Stizostedion canadense) and freshwater drum (Aplodinotus grunniens) were fish hosts for glochidia of L. higginsii (Surber, 1912; Wilson, 1916; Coker et al., 1921). These identifications were based on examination of natural infestations, but field identifications are not robust (Waller and Holland-Bartels, 1988; Waller and Mitchell, 1988); Hove and Kapuscinski (2002), however, confirmed sauger as a suitable host. Based on laboratory infestations of fish with L. higginsii glochidia, Waller and Holland-Bartels (1988) indicated that four species of fish were suitable hosts: largemouth bass (Micropterus salmoides), smallmouth bass (M. dolomieu), walleye (Stizostedion vitreum vitreum) and yellow perch (Perca flavescens). There was some transformation of glochidia to juveniles on green sunfish (Lepomis cyanellus), whereas two species, bluegill (Lepomis macrochirus) and northern pike (Esox lucius), were considered marginal hosts, because each produced only one juvenile. The common carp (Cyprinus carpio) and fathead minnow (Pimephales promelas) were unsuitable hosts. Studies by Waller and Holland-Bartels (1988) and Waller and Mitchell (1988) supported those by Sylvester et al. (1984) that walleye and largemouth bass were hosts for L. higginsii, but Sylvester et al. (1984) indicated that the green sunfish and bluegill were not suitable hosts. Hove and Kapuscinski (2002) confirmed largemouth bass as suitable hosts and found that sauger and black crappie also facilitated metamorphosis of L. higginsii glochidia. Lampsilis higginsii is a long-term brooder (bradytictic). Glochidial release has been reported during June and July and May and September. Glochidia of L. higginsii are morphologically similar to those of several other species of lampsilines in the Upper Mississippi River. Waller and Mitchell (1988) have shown that Lampsilis higginsii glochidia can be differentiated from L. cardium, L. siliquoidea, and Ligumia recta by electron microscopy; they could not be differentiated by light microscopy or morphometric measures.
Habitat Type: Freshwater
Non-Migrant: Y
Locally Migrant: N
Long Distance Migrant: N
Riverine Habitat(s): BIG RIVER, MEDIUM RIVER
Special Habitat Factors: Benthic
Habitat Comments: This species is found in substrates of mud with a mixture of gravel and stones. It prefers rapidly flowing water (USFWS, 1982). Lampsilis higginsii is characterized as a large river species occupying stable substrates that vary from sand to boulders, but not firmly packed clay, flocculent silt, organic material, bedrock, concrete or unstable sand. Water velocities should be less than 1 m/second during periods of low discharge. They are usually found in mussel beds that contain at least 15 other species at densities greater than 0.01 individual/square meter. In the Mississippi River, the density of all mussels in the bed typically exceeds 10/square meter (USFWS, 1982; Hornbach, 2004). Although historical distribution includes tributaries with a wide range in average mean discharge, current recruiting populations now inhabit rivers with mean annual discharge greater than 500 cubic feet per second suggesting Lampsilis higginsii inhabits large rivers, not small tributaries (Miller and Payne, 2007).
Adult Food Habits: Planktivore
Food Comments: From USFWS (2004): Among the few published studies on unionid feeding mechanisms are recent studies by Tankersley and Dimock (1992, 1993a, 1993b) who used endoscopic techniques to examine feeding in Pyganodon cataracta. There have been no studies focusing specifically on L. higginsii but generally unionids are filter-feeders, removing small suspended food particles from the water column utilizing the large lamellibranch gills as feeding organs. Feeding rate in bivalves is known to be greatly influenced by temperature, food concentration, food particle size and body size (Jørgensen 1975; Winter 1978).

Adult Phenology: Circadian
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: This species was listed as federally endangered in the U.S. in 1976 and a recovery plan (USFWS, 2004) created. Reintroductions have occurred since 2000 into 4 rivers from which it had previously been extirpated (USFWS, 2004), including pool 4 and the Twin Cities region nof the Mississippi River below St. Anthony Falls, Minnesota (Sietman, 2003). The first recovery plan (USFWS, 1983) included six locations in the Upper Mississippi River and one in the St. Croix River as essential habitats because they supported viable reproductive populations and the second recovery plan (USFWS, 2004) identified 3 more (1 in the Wisconsin River and 2 in the St. Croix River), identifying these regions as "Essential Habitat Areas (EHA). EHAs are those sites with at least 0.25% of the mussel fauna identified as Lampsilis higginsii, a dense assemblage (>10/ square meter), and contained at least 15 species (each > 0.01/square meter). The plan recommended downlisting to threatened if populations in 5 EHAs were reprducing, self-sustaining, and not threatened by zebra mussels; and delisted if populations in 5 EHAs met the above criteria and were sufficiently secure to assure long-term viability.
Restoration Potential: This species has received more conservation aid than any other mussel and is the subject of a federal recovery plan. It has been transplanted with at least initial success. Since the inception of the recovery plan, additional populations have been discovered, some containing numerous individuals. It has been suggested by some workers that it be delisted from the endangered status. Because of this attention, this species may be a good candidate for man-mediated recovery and conservation within its remaining range.
Management Requirements: Refer to the General Freshwater Mussel ESA.
Biological Research Needs: Relocation and translocation away from zebra mussels. Develop propagation techniques.
Population/Occurrence Delineation
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Group Name: Freshwater Mussels

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on some evidence of historical or current presence of single or multiple specimens, including live specimens or recently dead shells (i.e., soft tissue still attached and/or nacre still glossy and iridescent without signs of external weathering or staining), at a given location with potentially recurring existence. Weathered shells constitute a historic occurrence. Evidence is derived from reliable published observation or collection data; unpublished, though documented (i.e. government or agency reports, web sites, etc.) observation or collection data; or museum specimen information.
Mapping Guidance: Based on the separation distances outlined herein, for freshwater mussels in STANDING WATER (or backwater areas of flowing water such as oxbows and sloughs), all standing water bodies with either (1) greater than 2 km linear distance of unsuitable habitat between (i.e. lotic connections), or (2) more than 10 km of apparently unoccupied though suitable habitat (including lentic shoreline, linear distance across water bodies, and lentic water bodies with proper lotic connections), are considered separate element occurrences. Only the largest standing water bodies (with 20 km linear shoreline or greater) may have greater than one element occurrence within each. Multiple collection or observation locations in one lake, for example, would only constitute multiple occurrences in the largest lakes, and only then if there was some likelihood that unsurveyed areas between collections did not contain the element.

For freshwater mussels in FLOWING WATER conditions, occurrences are separated by a distance of more than 2 stream km of unsuitable habitat, or a distance of more than 10 stream km of apparently unoccupied though suitable habitat. Standing water between occurrences is considered suitable habitat when calculating separation distance for flowing water mussel species unless dispersal barriers (see Separation Barriers) are in place.

Several mussel species in North America occur in both standing and flowing water (see Specs Notes). Calculation of separation distance and determination of separation barriers for these taxa should take into account the environment in which the element was collected. Juvenile mussels do not follow this pattern and juveniles are typically missed by most standard sampling methods (Hastie and Cosgrove, 2002; Neves and Widlak, 1987), therefore juvenile movement is not considered when calculating separation distance.

Separation Barriers: Separation barriers within standing water bodies are based solely on separation distance (see Separation Distance-suitable, below). Separation barriers between standing water bodies and within flowing water systems include lack of lotic connections, natural barriers such as upland habitat, absence of appropriate species specific fish hosts, water depth greater than 10 meters (Cvancara, 1972; Moyle and Bacon, 1969) or anthropogenic barriers to water flow such as dams or other impoundments and high waterfalls.
Separation Distance for Unsuitable Habitat: 2 km
Separation Distance for Suitable Habitat: 10 km
Alternate Separation Procedure: None
Separation Justification: Adult freshwater mussels are largely sedentary spending their entire lives very near to the place where they first successfully settled (Coker et al., 1921; Watters, 1992). Strayer (1999) demonstrated in field trials that mussels in streams occur chiefly in flow refuges, or relatively stable areas that displayed little movement of particles during flood events. Flow refuges conceivably allow relatively immobile mussels to remain in the same general location throughout their entire lives. Movement occurs with the impetus of some stimulus (nearby water disturbance, physical removal from the water such as during collection, exposure conditions during low water, seasonal temperature change or associated diurnal cycles) and during spawning. Movement is confined to either vertical movement burrowing deeper into sediments though rarely completely beneath the surface, or horizontal movement in a distinct path often away from the area of stimulus. Vertical movement is generally seasonal with rapid descent into the sediment in autumn and gradual reappearance at the surface during spring (Amyot and Downing, 1991; 1997). Horizontal movement is generally on the order of a few meters at most and is associated with day length and during times of spawning (Amyot and Downing, 1997). Such locomotion plays little, if any, part in the distribution of freshwater mussels as these limited movements are not dispersal mechanisms. Dispersal patterns are largely speculative but have been attributed to stream size and surface geology (Strayer, 1983; Strayer and Ralley, 1993; van der Schalie, 1938), utilization of flow refuges during flood stages (Strayer, 1999), and patterns of host fish distribution during spawning periods (Haag and Warren, 1998; Watters, 1992). Lee and DeAngelis (1997) modeled the dispersal of freshwater into unoccupied habitats as a traveling wave front with a velocity ranging from 0.87 to 2.47 km/year (depending on mussel life span) with increase in glochidial attachment rate to fish having no effect on wave velocity.

Nearly all mussels require a host or hosts during the parasitic larval portion of their life cycle. Hosts are usually fish, but a few exceptional species utilize amphibians as hosts (Van Snik Gray et al., 2002; Howard, 1915) or may metamorphose without a host (Allen, 1924; Barfield et al., 1998; Lefevre and Curtis, 1911; 1912). Haag and Warren (1998) found that densities of host generalist mussels (using a variety of hosts from many different families) and displaying host specialists (using a small number of hosts usually in the same family but mussel females have behavioral modifications to attract hosts to the gravid female) were independent of the densities of their hosts. Densities of non-displaying host specialist mussels (using a small number of hosts usually in the same family but without host-attracting behavior) were correlated positively with densities of their hosts. Upstream dispersal of host fish for non-displaying host specialist mussels could, theoretically, transport mussel larvae (glochidia) over long distances through unsuitable habitat, but it is unlikely that this occurs very often. D. Strayer (personal communication) suggested a distance of at least 10 km, but a greater distance between occurrences may be necessary to constitute genetic separation of populations. As such, separation distance is based on a set, though arbitrary, distance between two known points of occurrence.

Date: 18Oct2004
Author: Cordeiro, J.
Notes: Contact Jay Cordeiro (jay_cordeiro@natureserve.org) for a complete list of freshwater mussel taxa sorted by flow regime.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 25Jun2010
NatureServe Conservation Status Factors Author: Cordeiro, J. (2010); Whittaker, J.C.; revised by M. Morrison (1995)
Management Information Edition Date: 13Sep2007
Management Information Edition Author: Cordeiro, J. (2007) WATTERS, THOMAS G. (Ohio State University) (1987)
Element Ecology & Life History Edition Date: 13Sep2007
Element Ecology & Life History Author(s): Cordeiro, J.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • Baker, F. C. 1928.  The fresh water mollusca of Wisconsin:  part II: Pelecypoda.  Wisconsin Geological and Natural History Survey Bulletin No. 70, Part II.  University of Wisconsin, Madison.  495 pp.

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  • Howard, A.D. 1915. Some exceptional cases of breeding among the Unionidae. The Nautilus 29:4-11.

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  • Matthews, J.R. and C.J. Moseley (eds.). 1990. The Official World Wildlife Fund Guide to Endangered Species of North America. Volume 1. Plants, Mammals. xxiii + pp 1-560 + 33 pp. appendix + 6 pp. glossary + 16 pp. index. Volume 2. Birds, Reptiles, Amphibians, Fishes, Mussels, Crustaceans, Snails, Insects, and Arachnids. xiii + pp. 561-1180. Beacham Publications, Inc., Washington, D.C.

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  • Mueller, L. 1993. Winged mapleleaf mussel and Higgins eye pearly mussel: freshwater mussels threatened with extinction. Minnesota Department of Agriculture. Booklet, 19 pp.

  • Nelson, D.A. and T.M. Freitag. 1980. Ecology, identification and recent discoveries of Higgin's eye (Lampsilis higginsi), spectacle case (Cumberlandia monodonta), and fat pocketbook (Potamilis capax) mussels in the upper Mississippi River. Pages 120-148 in J. Rasmussen (ed.), Proceedings of the UMRCC Symposium on the Upper Mississippi River Bivalve Molluscs. Upper Mississippi River Conservation Committee, Rock Island, Illinois.

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  • Sietman, B. E. 2003. Field guide to the freshwater mussels of Minnesota. Minnesota Department of Natural Resources, St. Paul, Minnesota. 144 pp.

  • Sietman, B.E. 2003. Field Guide to the Freshwater Mussels of Minnesota. Minnesota Department of Natural Resources: St. Paul, Minnesota. 144 pp.

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References for Watershed Distribution Map
  • Cummings, K.S. and C.A. Mayer. 1997. Distributional checklist and status of Illinois freshwater mussels (Mollusca: Unionacea). Pages 129-145 in: K.S. Cummings, A.C. Buchanan, C.A. Mayer, and T.J. Naimo (eds.) Conservation and management of freshwater mussels II: initiatives for the future. Proceedings of a UMRCC Symposium, October 1995, St. Louis, Missouri. Upper Mississippi River Conservation Committee, Rock Island, Illinois.

  • Miller, A.C. and B.S. Payne. 2007. A re-examination of the endangered Higgins eye pearlymussel Lampsilis higginsii in the upper Mississippi River, USA. Endangered Species Research, 3: 229-237.

  • U.S. Fish and Wildlife Service (USFWS) (Hornbach, D.J.) 2004. Higgins eye pearlymussel (Lampsilis higginsii) recovery plan: first revision. U.S. Fish and Wildlife Service, Ft. Snelling, Minnesota. 126 pp.

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