Triannual Unionid Report
Report No. 9
May 1996
A forum for the informal exchange of information on the status of
North American unionid research, management, and conservation
Richard G. Biggins
U.S. Fish and Wildlife Service
160 Zillicoa Street
Asheville, North Carolina 28801
NOTE: The intent of this report is to expedite the exchange of information in an
informal format. Report submissions were solicited from individuals and
agencies involved in unionid conservation. The submissions were not edited.
They were copied as received and assembled into the report.
The report was then scanned to create this Web site.
The mussel above was drawn by an elementary school student as part of a contest
to design the character "Russell the Mussel" held by the Tennessee Aquarium, Chattanooga, Tennessee.
TABLE OF CONTENTS
TRIANNUAL UNIONID REPORT NO. 9
MAY 1996
Hoke, E.
The unionid mollusks of the Big and Little Nemaha Rivers of southeastern Nebraska and northeastern Kansas.
Strayer, D. L. and L. C. Smith
Zebra mussels may kill unionids without fouling them.
Bowers-Altman, J.
Dwarf wedgemussels of the Pequest River, Warren County, New Jersey.
McMurray, S. E. and G. A. Schuster
An investigation into reproduction in a unionid bed impacted by a dam with hypolimnionic drain.
Garner, J. T.
Alabama Game and Fish Division malacology program: 1) mussel population assessments/Tennessee River; 2) reproductive biology studies of Potamilus alatus, Obliquaria reflexa, and Megalonaias nervosa; and 3) pamphlet of the commercial mussels of Alabama.
Schueler, F. W.
A survey of the unionid mussels of the Rideau and Lower Ottawa drainages (in Ontario).
Watters, G. T.
1996. Small dams as barriers to freshwater mussels (Bivalvia: Unionoida) and their hosts. ABSTRACT FROM: Biological Conservation. 75:79 85.
Watters, G. T.
Cross polarized light to detect glochidia.
Watters, G. T.
Glochidia overwintering on host.
Watters, G. T.
New host for Lampsilis cardium.
Ahlstedt, S.
USGS NAWQUA study unit upper Tennessee River tributaries and Steve's new address and phone number.
Neves, R. J.
Information request: Requesting a list of researchers and research projects on aquatic bivalves in the Ohio River drainage.
Neils, D. E. and R. J. Neves
Large scale relocation of native unionids from Kentucky Lake (Tennessee River) to an upper Tennessee River tributary (Holston River).
Liu, H. and M. Mulvey
Genetic relationship among some Elliptio species: RFLPs analysis of amplified ITS region.
Hove, M. C. Considerations when conducting host suitability tests.
Havlik, M. E. Shall I age my unionids? Is a poor age estimate better than no age information?.
Haag, W. R. and M. L. Warren, Jr. Host Fishes of some Mobile Basin unionids.
Altaba, C. R. News about Margaritifera auricularia.
Waller, D. L., J. J. Rach, W. G. Cope, and G. A. Miller. 1995. Effects of handling and aerial exposure on the survival of unionid mussels. ABSTRACT FROM: Journal of Freshwater Ecology. 10(3)199.
Cope, W. G. and D. L. Waller.1995. Evaluation of freshwater mussel relocation as a conservation and management strategy. ABSTRACT FROM: Regulated Rivers: Research & Management. 11:147-155.
Author: Ellet Hoke
Address: 13931 Reflection Ct. #736, Ballwin, MO 63021
Phone: (314) 391 9459
The Unionid Mollusks of the Big and Little Nemaha Rivers of Southeastern Nebraska and Northeastern Kansas
The unionid mollusks of the Big Nemaha and Little Nemaha Rivers have been relatively unstudied as have the unionids of Nebraska and northern Kansas in general. In conjunction with a project to document the unionid distributions of this region, 87 sites were collected in the Nemaha basins between 1976 and 1995 Sites were collected by hand or with the use of a garden rake under low water conditions.
A total of 28 taxa were confirmed for the region in this study. One bivalve, Alasmidonta marginata, was documented through a museum record. In addition, twenty seven taxa were collected during this survey of the Nemaha basins. Twenty one of these document taxa first reported, though apparently unvouchered, by Aughey (1877). The remaining six taxa, Arcidens confragosus, Quadrula p. pustulosa, Obovaria olivaria, Truncilla donaciformis, Toxolasma parvus, and Lampsilis t. teres are first reported from the study area in this survey.
The unionid fauna of the region appears to have been largely destroyed. Most of the bivalves collected during the survey were represented solely by weathered or chalky shells. Only eight taxa were collected live or as relatively fresh shells, suggesting a possible decrease in the documented unionid fauna of the study area of as much as 71%. The most widely distributed bivalves recovered were Amblema p. plicata, Fusconaia flava, Strophitus u. undulatus, and Ligumia subrostrata. With one exception, all occurrences of each of these taxa were as weathered shells only. A single specimen of L. subrostrata was collected as a fresh shell at one location in northeastern Kansas.
The demise of the unionid fauna of the Nemaha basins is no doubt the product of a number of factors, however, channelization is probably the most significant of these. Beginning in 1904, both river basins were heavily channelized with a resultant loss of 164 river miles or 11.4 percent of their original stream mileage. Channelization was most heavily concentrated in the larger streams of the region where the greatest bivalve diversity was probably once located. Additional factors impacting unionids in the region include siltation, feedlot runoff and, probably, chemical pollution from pesticides and herbicides.
Aughey, Samuel. 1877. Catalogue of the land and freshwater shells of Nebraska. Bulletin of the U.S. Geological and Geographical Survey of the Territories 3(3): 697 704.
David L. Strayer and Lane C. Smith
Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545
phone: (914) 677 5343
fax: (914) 677 5976
email: dlstrayer@aol.com
Zebra mussels may kill unionids without fouling them
We have been monitoring the unionid community (Elliptio complanata, Anodonta implicata, Leptodea ochracea) of the freshwater tidal Hudson River through the zebra mussel invasion (1991 95). Although zebra mussels have been abundant in the river since September, 1992 (riverwide mean =600-4000 m 2), few of the unionids have been infested by zebra mussels. Infestation rates have hovered around 30%, with no difference among unionid species, and most infested animals carry only 1 2 zebra mussels. We have no idea why our infestation rates are so low. Despite these low infestation rates, the unionid community has declined sharply since the zebra mussel arrived: density is down by 56%, recruitment of young year is down by 90%, and condition (body mass at a given shell length) is down by 20 50%. Elliptio appears to be less severely affected than the other species. We believe that these impacts have occurred not from fouling, but from competition for food: zebra mussels have reduced the biomass of phytoplankton in the Hudson to 15% of the pre invasion levels. Our results emphasize that fouling is not the only way in which zebra mussels can strongly affect unionids; impacts through the food web must be considered as well.
A manuscript describing our findings will be submitted this month (April).
Department of Environmental Protection
Division of Fish, Game and Wildlife
Robert McDowell, Director
CN 400
Trenton, NJ 08625
609-292-2965
609-984-1414 FAX
Jeanette Bowers-Altman, Senior Zoologist
Endangered and Nongame Species Program
Shells of the federally endangered dwarf wedgemussel (Alasmidonta heterodon) were recently discovered in the Pequest River in Warren County, New Jersey. During the months of August and September 1995, nine A. heterodon valves and 11 partial valves and fragments were recovered on state property by zoologists from the Division of Fish, Game and Wildlife's Endangered and Nongame Species Program (ENSP) and the Division of Parks and Forestry's Natural Heritage Program (NHP). Although no live A. heterodon were located, the host fish species tessellated darter (Etheostoma olmstedi) was abundant throughout the study area. Surveys focusing on the previously unknown site are scheduled to continue in the spring of 199B. The ENSP dwarf wedgemussel survey is made possible through USFWS Section 6/ federal aid funding.
Authors: Stephen E. McMurray and Guenter A. Schuster
Address: Department of Biological Sciences
Eastern Kentucky University
Richmond, Kentucky 40475 3124
(606) 622 2280 & (606) 622 1016
e mail:
STUMCMUR@ACS.EKU.EDU
BIOSCHUS@ACS.EKU.EDU
An Investigation Into Reproduction in a Unionid Bed Impacted by a Dam with a Hypolimnionic Drain
One of the most perplexing problems of unionid conservation is the documented loss of recruitment (reproduction) in some unionid beds. The freshwater unionid bed in the Licking River at Moores Ferry, Kentucky, is a diverse bed consisting of 29 unionid species, as well as Corbicula fluminea. Unionid densities were found to average 7.98/m2 and C. fluminea was found to have an average density of 300.66/m2, while no juvenile unionids (<20 mm in length) were found (Smathers 1990). These results were supported by Kane (1990) while studying the feeding habits of muskrats. Kane (1990) sampled a total of 23 muskrat middens over an eight month period. A total of 6814 bivalve shells, comprising 13 species of unionids and C. fluminea were collected. None of the unionid shells found were juveniles. These two studies suggested that recruitment had ceased or was dramatically decreased in this diverse unionid bed.
An objective of our present work is to determine if recruitment has ceased in this unionid bed, and if it has, to determine where in the life cycle reproduction is breaking down. Is it: 1. During gametogenesis so that eggs and sperm are not even produced?; 2. That there is no fertilization so that glochidia are not produced?; 3. That glochidia are produced, but for some reason do not infect host fishes?; 4. That host fishes are infected, but the glochidia do not properly mature and form juvenile mussels?; or 5. A combination of all these factors? Another objective of this study is to determine what effects, if any, that the hypolimnionic discharge from the dam at Cave Run Reservoir is having on the unionids in this bed. It is hypothesized that the loss of recruitment in this bed is either directly or indirectly the result of the dam, which is located approximately 3S.4 km upstream from Moores Ferry. It is hypothesized that the discharge from the dam has altered both the natural temperature and flow regimes of the river.
Unionids in this bed and another bed approximately 194 km downstream from the dam have been examined on a monthly to bimonthly basis for the presence or absence of glochidia. Also, five individuals of two target species, Elliptio dilatata and Actinonaias ligamentina are collected each time, and returned to the lab to determine if gametogenesis is occurring. These species were chosen because they are the most common in this bed (Smathers 1990), they represent both reproductive strategies (bradytictic and tachytictic) of freshwater unionids, and they are commonly encountered throughout their respective ranges (Oesch 1984). Fish are also collected at the same time and returned to the lab to examine them for the attachment of glochidia. Finally, drift nets are being set out for one hour at each site to determine if glochidia are being released. In addition to this, temperature and discharge data for the Licking River at Farmers, Kentucky, which is near Moores Ferry, have been obtained from the USGS. Since Farmers is an historical site, temperature and discharge data are available for recent times, as well as preimpoundment times (pre 1974). With all of these data, we hope to show that the regulated flow from the dam at Cave Run Reservoir has had an adverse effect on the freshwater unionids in this bed.
One juvenile Actinonais ligamentina has been found in the bed attached to an adult of the same species by a byssal threat, and preliminary data indicate that the production of glochidia is occurring. It is apparent that reproduction may be occurring, but that it is clearly decreased. It is not yet known what the exact reproductive success of this bed is. Preliminary data also seem to indicate that the decrease in reproduction is in part the result of either: 1. Glochidia not attaching to host fish(es); 2. The encystment period being affected by water temperature; or 3. Glochidia being prematurely expelled because of extreme water temperature changes caused by the release of water from the tam.
Literature Cited:
Kane, M.A. 1990. The predation of freshwater bivalves by muskrats (Ondatra zibethicus) in the Licking River, at Moores Ferry, Kentucky. MS Thesis, Eastern Kentucky University, Richmond, Kentucky. 64 pp.
Oesch, R.D. 1984. Missouri naiades: a guide to the mussels of Missouri. Missouri Department of Conservation. 270 pp.
Smathers, K.L. 1990. An analysis of a bivalve (Mollusca: Bivalvia) community in the Licking River, at Moores Ferry, Kentucky. MS Thesis, Eastern Kentucky University, Richmond, Kentucky. 65 pp.
Jeffrey T. Garner
Alabama Game and Fish Division
P.O. Box 366
Decatur, AL 35602
(205) 232-2101
fax 240-0402
The Alabama Game and Fish Division malacology program got under way a little over a year ago. Most of the first year was spent getting equipped for field work, locating study sites for mussel population assessments and perfecting data collection methods. Following is a list of current ongoing activities.
Mussel Population Assessments
Three sample stations were established on the Tennessee River during the summer of 1995. These stations will be quantitatively sampled periodically (annually or biennially) in order to monitor the health the populations. Due to time constraints, data were collected from only one site last year. During the 1996 field season, work will continue on the Tennessee River and sites will be established on the Alabama River system.
In addition to the quantitative population assessments, a catch per unit effort study is being carried out. These methods, which are much less demanding on time and resources, allow a larger portion of the state to be sampled. The sampling is aimed at determining the effects of commercial harvest on mussel populations. These data, used along with the quantitative assessments, should give an accurate picture of the health of Alabama's mussels.
Reproductive Biology Studies
In conjunction with the University of North Alabama, studies on the reproductive biology of Potamilus alatus, Obliquaria reflexa and Megalonaias nervosa are underway. Monthly samples have been collected since July 1995. Histological sectioning of the specimens is underway. Quantitative assessment of gametogenesis in the specimens will be carried out later this year, beginning with P. alatus.
Mussel Pamphlet
Alabama Game and Fish Division has funded the production of a pamphlet on commercial mussels in the state. Each commercial species is described along with a full color photograph. The pamphlet also contains introduced species and endangered mussels which may be confused with commercial species. It is being prepared by Monte McGregor and is near completion.
Frederick W. Schueler
Biological Checklist of the Kemptville Creek Drainage Basin, Bishops Mills, RR#2 Oxford Station, Ontario K0G 1T0 Canada
(613)258 3107 (no fax or email address)
A SURVEY OF THE UNIONID MUSSELS OF THE RIDEAU AND LOWER OTTAWA DRAINAGES (in Ontario).
A.H. Clarke (Freshwater Mollusks of Canada, 1981), working from the now Canadian Museum of Nature (CMN) collection, mapped 15 unionid species in Eastern Ontario. In 1995, in a survey commissioned by the Ontario Ministry of Natural Resources, I found Elliptio complanata, Lampsilis radiata, & Anodonta grandis ubiquitously. In order of decreasing abundance, Lasmigona compressa, L. costata, Strophitus undulatus, Lampsilis ventricosa, & Anodontoides ferussacianus are widespread in suitable habitat. Ligumia recta is found at several sites near Ottawa. I found Leptodea fragilis, Elliptio dilatata, & Ligumia nasuta at single sites, but not Obovaria olivaria, Alasmidonta undulata, or A. marginata, though I did not search the few sites where they had been known. I found no evidence that any species had been extirpated, but found introduced Zebra Mussels (Dressensa polymorpha) only in the Rideau River at Monotick.
Most of the unionids in the Ottawa area were found by collections made in 1881 1882. This & subsequent CMN collecting was not! directed towards a systematic survey, & resulted in no collections at all from the Kemptville Creek, Jock, & Tay drainages, & very few from the Mississippi or South Nation drainages. It is still possible to find almost all of the fecal species in a couple of years. The largest valve collected in 1993 1995 was larger than the largest found historically (1881 1980) in seven species, while there were only four species where the largest historic valve was larger (about 200 lots in each sample), & the relative abundances of species were similar. ~
The Jock River supports a rich fauna, while diversity on Kemptville Creek peaks below the Oxford Mills dam. Shells were abundant at Perth on the Tay. All three streams had very few unionids at their mouths in the Rideau Canal. One station on the Rigaud supports several species. The ubiquitous species all participate in hybrid zones. Many lower Ottawa River Elliptio appear intermediate between the widespread E. complanata & E. dilatata. Anodonta grandis & A. cataracta hybridize, & hybrids between the species or subspecies Lampsilis (r.) radiata & L. (r.) siliquoidea are not described by Clarke, who did not have samples from the streams where they are largest.
I hope to publish an account of this fauna after another season of surveying streams & lakes I could not get to in 1995. The Ottawa River, the South Nation, & most lakes will be best surveyed by boat. Eastern drainages, & the Castor, Tay & Mississippi can still be explored by vehicle. Deep water sampling will require scuba diving.
G. Thomas Watters
Aquatic Ecology Laboratory & Museum of Biological Diversity, Ohio State University
1314 Kinnear Rd., Columbus, OH 43212-1194
voice: 614 292 6170
fax: 614 292 0181
email: gwatters@magnus.acs.ohio-state.edu
1. New publication
Watters, G.T. 1996. Small dams as barriers to freshwater mussels (Bivalvia: Unionoida) and their hosts. Biological Conservation 75:79 85.
Abstract. The distributions of two unionoids (fragile papershell, Leptodea fragilis, and pink heelsplitter, Potamilus alatus) were examined in five North American Midwest river systems in relation to the location of dams on the rivers. These dams were non navigational (without locks), lacked fish ladders, and varied in height from 1 to 17.7 m. Both species were restricted in their distribution to the river downstream of the dams. This suggests that the host fish(es) of these species was unable to move upstream of these obstacles. Both unionoids are believed to parasitize the freshwater drum (Aplodinotus grunniens). Several endangered unionoid species also may use this fish, or other dam limited fishes, as hosts. Dams, even lowhead structures, may contribute to the overall depletion of unionoids by artificially restricting their distributions and isolating populations from each other. Management practices for endangered fishes and mussels must take into account these physical obstacles.
2. Cross polarized light to detect glochidia
Glochidia may be difficult to detect and count in samples containing zooplankton, algae, fish waste, etc. We use cross polarization to greatly improve the efficiency of examining these types of samples. A polarized filter is attached to the nose of a dissecting microscope, and a sheet of polarized film is taped to the glass stage. By rotating the filter, light becomes cross polarized. This sharply illuminates glochidial shells, either open or closed. Transformed individuals appear darker than untransformed ones, and the paired adductor muscles are clearly visible. Non prismatic material such as algae, chitin, and feces are not illuminated, but sand grains and other prismatic shell material (ostracodes, zebra mussels, etc.) are illuminated. We found this technique indispensable in sorting samples containing numerous bivalved cladocerans of the same size as glochidia, and in detecting glochidia in fish waste. Samples may be counted faster, with greater ease, and at lower magnifications using this method.
This technique was first used to detect zebra mussel veligers in zooplankton samples: Johnson, L. E. 1995. Enhanced early detection and enumeration of zebra mussel (Dreissena ssp.) veligers using cross polarized light microscopy. Hydrobiologia 312: 139. We thank Dr. Dave Culver, Ohio State University, for demonstrating the technique.
3. Glochidia over wintering on hosts preliminary results
We assume that some mussels parasitize their hosts in the fall and that the glochidia overwinter on the fishes. The degree of mortality associated with this overwintering is unknown. How long glochidia may be maintained at winter temperatures, and still metamorphose when exposed to warmer temperatures, also is unknown. Our recent experimental work suggests that metamorphosis will not take place, or takes place at a greatly reduced rate, at 13ºC. When the host is brought to 21ºC, transformation begins. For this preliminary study, we infected hatchery raised largemouth bass (LMB) with Lampsilis cardium. As a control, LMB were parasitized at 13ºC and then brought to 21ºC. Transformation occurred from day 15 to 43, with a mode of day 25. A second group was parasitized and held at 13ºC for 46 days before being brought to 21ºC. Transformation began after three days and lasted 28 days, with a mode of 17 days post "warming." A third group was parasitized and held at 13ºC for 64 days before being brought to 21ºC. Transformation began after three days and lasted 20 days, with a mode of 15 days post "warming." No increased mortality is evident with this overwintering. Once warmed, glochidia metamorphose faster than the control by approximately one week. Apparently, glochidia undergo some development even at winter temperatures, but do not transform. We have begun a more comprehensive experiment that will study this phenomenon over seven months of "winter."
Control. Hosts parasitized at 13ºC, then brought to 21¡C immediately afterward.
insert graph
Hosts parasitized and held at 13ºC for 46 days, then brought to 21ºC (arrow).
insert graph
Hosts parasitized and held at 13ºC for 64 days, then brought to 21ºC (arrow).
insert graph
4. New hosts for Lampsilis cardium
Two new hosts are reported for Lampsilis cardium based on laboratory infections. At 21ºC, 30% of attached glochidia transformed on green sunfish between 33 and 47 days post infection. At 21ºC, 4% of attached glochidia transformed on western banded killifish between 13 and 19 days
Steven Ahlstedt
U. S. Geological Survey
1820 Midpark Drive
Knoxville, TN 37921
Phone: (423) 545-4140 or 545-4141 (Ext. 17)
FAX: (423) 545-4496
The UTEN NAWQA study unit will commence biological sampling beginning the week of May 6. The following sites will be sampled for fish, benthic macroinvertebrates, mollusks, and algae:
Clinch River @ Tazewell, TN
Copper Creek near Gate City, VA (intensive site)
Middle Fork Holston River, VA @ seven mile ford (intensive site)
Nolichucky River @ Lowlands, TN
Nolichucky River @ Embreeville, TN
Big Limestone Creek near Limestone, TN (intensive site)
Guest River, VA just above confluence with Clinch River
French Broad River near Newport, TN
Pigeon River near Newport, TN
Holston River @ Surgoinsville, TN
Powell River @ Arthur, TN
Weekly water quality, pesticides, and bacteriological sampling are taken at the intensive sites. The remaining sites are sampled monthly for water quality.
Synoptic collections will also be performed in the Clinch Powell Holston River drainages in conjunction with TVA's river action teams (RAT). TVA is our major contractor for helping us sample fish at these sites. Contract person for fish at TVA is Charlie Saylor (423) 632 1779.
My old address and phone numbers at TVA are no longer valid since the USGS has moved into new quarters. Please use the above address and phone numbers. Thanks!
RICHARD J. NEVES
Virginia Cooperative Fish and Wildlife Research Unit, Virginia Tech, Blacksburg, VA 24061
Phone: (540) 231 5927, FAX: (540) 231 7580
email: mussel@vt.edu
INFORMATION REQUEST
The mussel subgroup of the Ohio River Valley Ecosystem Team has requested that I compile a list of researchers and research projects on aquatic bivalves within the Ohio River drainage. If you are conducting any research, monitoring, or periodic sampling for native or exotic mollusks within tributaries or the main stem Ohio River, please contact me. If you aren't but know of someone who is, please pass along their name to me. I hope to be able to compile a list of who's doing what in the Ohio River Valley.
David E. Neils and Richard J. Neves
Virginia Cooperative Fish and Wildlife Sciences
Department of Fisheries and Wildlife Sciences
Virginia Polytechnic Institute and State University
Blacksburg, VA 24061 0321
(540) 231 5927
(540) 231 5780
Large scale relocation projects have been suggested as a proactive management strategy to protect native unionid populations in southeastern rivers and lakes from the negative effects of the ever encroaching zebra mussel (Dreissena polymorpha). This project is designed to explore the feasibility of relocating mussels from the Kentucky Lake region of the Tennessee River, which has already been inoculated with zebra mussels, to three sections of the upper Holston River (NFHRM 6.3 & 4.6, HRM 122), where inoculation is unlikely. Initial efforts of the project included collection, quarantining, and stocking of animals, as well as snorkel surveys which were completed during the summer and fall of 1995. Seasonal estimates of recovery and survival, and annual estimates of growth and gravidity will be utilized to determine the success of the relocation.
A total of approximately 5,000 animals of 8 different species were collected for relocation. Collection was completed by purchasing animals from a commercial shell buyer, hiring a commercial diver, or by TWRA divers. Of the animals collected, three ridge (Amblema plicata) comprised the largest proportion followed by, in descending order of abundance, ebonyshell (Fusconaia ebena), monkeyface (Quadrula metanevra), purple wartyback (Cyclonaias tuberculata), pimpleback (Quadrula pustulosa), washboard (Megalonaias nervosa), butterfly (Ellipsaria lineolata), and elephantear (Elliptio crassidens). Only five adult zebra mussels were found attached to the unionids collected. All animals were quarantined in 2400 liter aerated tanks for a period of 30 60 days to ensure that no zebra mussels were transferred from the site of collection to the relocation site. Following the quarantine period, no additional zebra mussels were found Approximately 1,000 animals died during the quarantine period, and most of those animals were purchased from the commercial shell buyer. Therefore, it is likely that much of the mortality can be attributed to desiccation and stress prior to quarantine.
Mussels were stocked in either large study reaches (~600-1000 m2 ) or smaller quadrats (9 m2 ) by individually placing each animal in the substratum. Animals plated in study reaches were identified by a file mark on their valve, while animals in quadrats were identified by a numbered tag. A total of 4,030 mussels were stocked as follows: NFHRM 6.3,1,907; NFHRM 4.6,977; HRM 122,1,146. The species composition relocated to NFHRM 6.3 and 4.6 were similar and consisted of three ridge (83%), purple wartyback (10%), and pimpleback (7%), while the species relocated HRM 122 were ebonyshell (44%), monkeyface (39%), washboard (10%), butterfly (4%), and elephantear (3%).
Fall snorkel surveys were completed at all sites to obtain baseline estimates of survival, recovery, and abundance. Visual observations during quadrat surveys at NFHRM 6.3 and 4.6 indicated that initial survival (~30 days) was similar among sites and ranged from 75 100% for all species, and that recovery success was high for three ridge (67 83%) but lower for purple wartyback (57 63%) and pimpleback (3260%). However, vertical migration in the substratum was believed to account for the lower recovery success of purple wartyback (45.8% buried)and pimpleback (19.4% buried). Transect surveys at NFHRM 6.3 and 4.6 also indicated that initial survival was high and similar among sites, ranging from 87 100% for all species. Survival of animals observed during transect surveys conducted at HRM 122 was 70%, slightly lower than NFHRM 6.3 and 4.6. Snorkel surveys are planned for the spring, summer, and fall of 1996. In addition to abundance and survival, estimates of gravidity, growth, and glochidial release will also be determined.
Genetic relationships among some Elliptio species: RFLPs analysis of amplified ITS region
Authors: Hsiu Ping Liu, and Margaret Mulvey
Address: Savannah River Ecology Laboratory, University of Georgia
P.O. Drawer E, Aiken, SC 29802
Phone Numbers: HPL: (803) 725-7095, MM: (803) 725-5786
Fax Number: (803) 725-3309
Email: liu@srel.edu
mulvey@srel.edu 2
Evolutionary studies of unionids have long been hindered by lack of an adequate species concept. The species concept that has been most frequently used is based almost entirely on conchology. The morphological variance within and among populations and species is so great that it is frequently difficult to distinguish species on the basis of conchology, especially genus Elliptio. The purposes of this study are: (1) to determine whether restriction fragment length polymorphisms (RFLPs) of ITS region could be used to differentiate Elliptio species and (2) to assess the relationships among 20+ Elliptiospecies.
Although study and analysis are ongoing, the following are our preliminary results and comments.
1. RFLPs of ITS region are useful to differentiate Elliptiospecies.
2. We would like to comment on the result of another RFLPs study. In 1996 newsletter, released by National Biological Service, Leetown Science Center at West Virginia, reported that E. fisheriana and E. producta are indistinguishable based on the RFLP analysis of ITS 1 region. However, in our RFLPs study; E. producta is significantly different from E. fisheriana. Several explanations are possible for the contradicting results.
a) Similar but different DNA regions were amplified. We amplified the entire ITS region that includes ITS-1, 5.8S and ITS-2 regions, NBS only amplified the ITS-1 region. Therefore, different fragment patterns would likely be obtained and lead to different conclusion.
b) Different restriction enzymes may have been used. It will again lead to different fragment patterns and conclusion. In our study, we found that most of the six base cutters are not informative.
c) "E. producta" specimens might be "E. fisheriana" Our study includes "E. producta" from Virginia and Georgia and "E. fisheriana" from Virginia. These names were applied based on shell features. We detect no genetic difference between "E. producta" from Virginia and "E. fisheriana," but significant difference between "E. producta" from Georgia and "E. fisheriana." E. producta from Georgia was taken from the Savannah River near Augusta, Georgia essentially the type locality. The name E. producta probably should be restricted to the phenotypes from the Savannah River and the name E fisheriana applied to those found in Virginia.
Considerations when conducting host suitability tests
Mark C. Hove, Department of Fisheries and Wildlife
Univ. of Minnesota, 1980 Folwell Ave., St. Paul, MN 55108
(612) 624-3019, mh@fw.umn.edu
Identification of fish hosts is a priority item listed under the basic biology research goal in the national strategy for freshwater mussel conservation (Biggins et al. 1995). Although protocols have been established for conducting host suitability tests (e.g., Zale and Neves 1982) you may want to consider these additional points.
Protect juvenile mussels from being consumed by test fish
The following observations have led me to believe that juvenile mussels should be protected from being consumed by suckers and small fish species during host suitability trials. On three occasions I've collected very few glochidia after inoculating white suckers and northern hog suckers. The catostomids quickly sloughed the glochidia and apparently consumed them after they fell to the bottom of the aquarium.
On another occasion I inoculated two groups of spotfin shiners with glochidia to determine if separating the fish from juveniles would increase the number of juveniles recovered. Eleven juveniles were recovered from five unrestricted shiners, while fifty-five juveniles were collected from six shiners that were prevented access to the bottom of the aquarium by a plastic screen. I suspect the unrestricted shiners consumed the juvenile mussels.
Test fish can be separated from juvenile mussels to avoid this problem. I've held fish in suspended nets and used false tank bottoms to separate fish from the tank bottom. However, siphoning under a suspended net is much easier than siphoning under a false tank bottom. Trdan and Hoeh (1986) designed a test chamber which separates fish from the mussels and enables the user to collect glochidia and juveniles without siphoning.
Check fish for glochidia before tests
Occasionally I've observed natural infestations of glochidia on test fish. I checked the fins and gills of each fish before conducting a study and replace those individuals which are already infested with glochidia. However, sometimes glochidia escape detection. I've collected Anodontine juveniles while studying Lampsiline glochidia. Holding test fish in warm water a month before conducting experiments will facilitate juvenile encystment. Repeated trials will help identify false positives.
Culture recovered juveniles
You can add a valuable component to your host suitability study by conducting culture experiments on the juveniles you've worked so hard to recover. Knowledge of juvenile mussel culture is badly needed if rare mussel reintroduction programs are to succeed.
Literature Cited
Biggins, R.G., R.J. Neves, and C.K. Dohner. 1995. Draft National strategy for the conservation of native freshwater mussels. USFWS, Asheville, NC. 26 pp.
Trdan, R.J., and W.R. Hoeh 1986. A chamber for monitoring glochidial infections of fish hosts. Malacological Review 19: 119-120.
Zale, A.V., and R.J. Neves. 1982. Fish hosts of four species of lampsiline mussels (Mollusca: Unionidae) in Big Moccasin Creek, Virginia. Can. J. Zool. 60: 2535-2542.
HAVLIK, MARIAN E.
Malacological Consultants, 1603 Mississippi Street, La Crosse, WI, 54601-4969
Phone/Fax: 608-782-7958
SHALL I AGE MY UNIONIDS? IS A POOR AGE ESTIMATE BETTER THAN NO AGE INFORMATION?
Field aging of unionids is a challenge. While amblemines have fairly distinct rest rings, lampsilines often have indentations rather than darkened rings. Age gives much more data to assess a unionid population rather than length alone. Using a large 1990 Prairie du Chien, WI, data set as a baseline, information has been compared from the Illinois, Meramec, Rock, and Mississippi rivers (including Lake Pepin). 1240 unionids were field aged on each valve; a mean age was determined for each specimen. Of these specimens, 42.1% were the same age, 31.2% were within one year of each age, 13.8% were within two years of each age, 7.5% were within three years of each age, and 5.5% had an age difference of four to six years. For each population, data has been compared as mean length/age class, abundance/age class, and abundance and mean age for size classes. Just over three percent of 754 Amblema p. plicata (Say, 1817) were less than 35 mm long, but they ranged from 2 - 7 years of age. Thirty-six seven year olds had the largest size range for an age class, 58 mm (31 to 89 mm long). At age 11 the range in length of 56 A. p. plicata was 27 mm (51 to 78 mm). At age 23 the range in length of 49 A. p. plicata was 25 mm. The overall mean length range for each age class was 24.7 mm. Two 67 mm long A. p. plicata from the same quadrat were eight and 23 years of age. Similarly, two Obliquaria reflexa Rafinesque, 1820, from the lower Rock River, IL, each 73 mm long, were seven and 25 years of age. Number/size class for A. p. plicata from Prairie du Chien showed the expected bell curve, but age data showed a bimodal distribution with a decline at 14 years corresponding to the large 1976 dredging. Age data on l00 specimens per species is preferred, and 200 specimens of a species per site gives good information on a population. In another study, using Lampsilis higginsi (Lea, 1857) from Prairie du Chien, WI, at least l0 specimens of each age class were measured, or back measured, to get data for each age class. At Prairie du Chien unionids only grow about two mm/year after sexual maturity. Age and length data for 200 A. p. plicata, obtained in 1988 on the Illinois River, showed among the most mean growth per age class. Unionids from Lake Pepin also showed a higher mean growth rate per age class than Prairie du Chien specimens. When analyzing commercial populations, height gives information on the age structure. Sixty-one A. p. plicata 65 mm high, ranged from 7 to 30 years of age. One hundred seven A. p. plicata that were over 67 mm (legal height) ranged from 13 to 32 years of age, yet five unionids over 27 years were not of a commercial height. A. H. Clarke's early 1990's Prairie du Chien data yielded a mean length per age distribution curve like ours, but Miller's 1995 extrapolation of Prairie du Chien data revealed a higher mean length for each age class, for essentially the same area. This means extrapolations must be very carefully done if aging is not done concurrently. So, learn how to age those unionids and look at your data from another perspective.
Host Fishes of Some Mobile Basin Unionids
Wendell R. Haag and Melvin L. Warren, Jr.
USDA Forest Service, Southern Research Station, Forest Hydrology Lab, Oxford, MS 38655
601-234-2744
Very little is known about fish hosts of mussels endemic to the Mobile Basin. Some of these species are among the most critically endangered in North America and host fish information is urgently needed. We are conducting host trials for several mussel species occurring in tributaries of the Black Warrior River system in Bankhead National Forest, Alabama. Our procedures largely have followed those of Zale and Neves (1982). Trials were run at 18-20¥C.
The following table summarizes our results as of April 29, 1996. Suitable hosts are those that produced transformed juvenile mussels; non-suitable hosts (NS) are those from which all glochidia were sloughed and no juveniles were produced. An asterisk (*) denotes a species that has carried glochidia for at least 10 days and continued to carry glochidia as of April 29. A question mark (?) denotes a species that carried glochidia for more than one week but all specimens died before completion of the trials. A dash (-) denotes a species that was not determined. LP = Lampsilis perovalis: SS = Strophitus subvexus; PG = Ptychobranchus greeni; VN = Villosa nebulosa.