Final Report US Department of The

Final Report U.S. Department of the Interior – Fish and Wildlife Service Arkansas Ecological Services Field Office

DISTRIBUTION AND POPULATION STRUCTURE OF FRESHWATER MUSSELS (BIVALVIA: UNIONOIDA) IN MIDDLE DITCH, BIG LAKE NATIONAL WILDLIFE REFUGE - ARKANSAS

Principal Investigator:

Chris L. Davidson U.S. Fish and Wildlife Service Arkansas Ecological Services Field Office Conway, AR 72032 [email protected]

January 2018

INTRODUCTION Big Lake National Wildlife Refuge (BLNWR), established in 1915, is comprised of 4,467 ha (11,038 ac) located in northeast Arkansas near Manilla, Mississippi County. BLNWR was a free- flowing river system until the New Madrid Earthquake of 1811-1812 shifted land and water flow to its present lake and swamp environment (https://www.fws.gov/refuge/Big_Lake/about.html). The watershed consists of approximately 6,475 km2 of agricultural land funneled into the refuge via several large drainage ditches within the St. Francis River basin (U.S. Fish and Wildlife Service 1976). In 1991, the U. S. Army Corps of Engineers constructed a series of water control structures to divert silt-laden floodwaters from the refuge and improve water quality and promote growth of natural aquatic vegetation. During the larval stage, mussels are obligate ectoparasites, attaching to the fins and gills of a host fish (Barnhart et al. 2008; Haag 2012). Larvae metamorphose into juveniles that excyst from the host fish and sink to the river bottom, where, if habitat is suitable, they continue their growth to adulthood. Some mussels are host generalists (i.e. using many species of fish), while others are host specialists (i.e. using one species of fish). Mussel dispersal and gene flow is a function of host fish movement. Changes in flow regimes of river systems affect dispersal potential and population structure of mussels and host fishes. Mussels are long-lived and relatively immobile. Therefore, they integrate environmental stressors occurring at multiple temporal and spatial scales (local to catchment) (Atkinson et al. 2012). Extensive systematic inventories of mussel fauna in the St. Francis River exist primarily as a result of efforts to determine the distribution and abundance of Fat Pocketbook (Potamilus capax) (Ahlstedt and Jenkinson 1987, 1991; Harris and Gordon 1987; Harris et al. 2009; Jenkinson and Ahlstedt 1987; Clarke 1985; Posey 1997). Mussel inventories have been conducted in selected sections of Stateline Outlet Ditch, which adjoins the eastern border of Big Lake Wildlife Management Area (abutting the eastern border of BLNWR) and Ditch No. 81 adjoining the western border of BLNWR, mostly to assess the potential effects of ditch cleanout and highway projects on mussels. In this report, I present the results of a mussel inventory from Middle Ditch. These data provide baseline information about the distribution and population structure of mussels within the portion of Middle Ditch that is located within the BLNWR boundary. BLNWR requested this information to better inform land and water management activities to conserve the mussel fauna at BLNWR.

METHODS Study Area

Middle Ditch diverges from Ditch No. 1 and traverses approximately 9.4 km of the “old” Little River channel before it converges with Big Lake (Figure 1). The northernmost point of Middle Ditch begins at a water control structure located on Ditch No. 1, approximately 16.7 km upstream of Arkansas Highway 18 (Figure 2). I used type of substrate, water depth, and

channel characteristics (e.g., meandering v. straight, channeling braiding or convergence, etc.) (Figures 2 – 7) to divide the study area into six sections. Section 1 was approximately 1,461 m in length and extended from Transect 1, near the water control structure, to the convergence of an overflow channel from Ditch No. 28 on river left facing downstream (35.98011, -90.11952; Figure 2). Mean width of wetted channel was 22.5 m. Water depth ranged from < 1 m to approximately 4 m. Substrate was dominated by hardpan clay near center channel and clay with silt near the margins of the wetted channel. Section 2 was approximately 1,179 m in length and extended from the terminus of Section 1 to Transect 53, where a noticeable sand bar extended nearly the entire width of the wetted channel (Figure 3). Mean wetted channel width was 23.1 m. Water depth ranged from 1 m near the lowermost third of this section to approximately 6 m in the upper two-thirds of it. Substrate in the deeper portion of this section was dominated by clay or sand with loose flocculent silt in the thalweg and clay with silt on descending banks. The shallower portion of this section was dominated by sand and clay with silt.

Figure 1. Study area for Middle Ditch mussel survey at Big Lake National Wildlife Refuge, 2017.

Figure 2. Location of Section 1 and mussel survey transects in Middle Ditch, Big Lake National Wildlife Refuge, 2017. Uppermost transect is approximately 50 m downstream of water control structure. Section 3 was approximately 1,179 m in length and extended from the terminus of Section 2 to Transect 78, just past the point where the channel braids (35.96291, -90.13067) (Figure 4). Mean width of wetted channel was 6.4 m (during a water drawdown). Water depth was ≤ 1 m, and a substantive portion of the normal wetted channel was dry during water drawdowns. Substrate was dominated by sand and clay with silt. Section 4 was approximately 1,345 m in length and extended from the terminus of Section 3 to Transect 80, which begins Section 5 (35.954589; -90.13295) (Figure 5). At this point, the channel widens substantially from the constricted channel width common to Section 4. The majority of this section was comprised of small (< 100 m2), shallow (≤ 1 m) pools with constricted, shallow channels (< 1 m wide and < 0.2 m deep) connecting pools. As a result, we determined while flagging transects that qualitative sampling in this section would be more informative for locating isolated pockets of mussels than transect sampling. The wetted channel ranged from < 1 m to approximately 10 m. Because we qualitatively sampled this

3 section, we did not measure mean width of wetted channel. Substrate was dominated by clay with silt.

Figure 3. Location of Section 2 and mussel survey transects in Middle Ditch, Big Lake National Wildlife Refuge, 2017.

Figure 4. Location of Section 3 and mussel survey transects in Middle Ditch, Big Lake National Wildlife Refuge, 2017.

Section 5 was approximately 1,581 m in length and extended from the terminus of Section 4 (35.95251; -90.13295) to Transect 110, which begins Section 6 (35.94396; -90.13063) (Figure 6). Mean width of wetted channel was 22.8 m. Water depth ranged from < 1 to 4 m. Substrate was dominated by clay with silt to clay or sand with loose flocculent silt in deeper (generally ≥ 3m) thalwegs. Section 6 was approximately 2,618 m in length and extended from the terminus of Section 5 to Big Lake at Transect 159 (35.92175, -90.13207) (Figure 7). Mean width of wetted channel was 22.8 m. Water depth ranged from 1 to 4 m. Substrate was dominated primarily by clay with silt with pockets of sand.

Figure 5. Location of Section 4 and qualitative mussel sample points in Middle Ditch, Big Lake National Wildlife Refuge, 2017.

Figure 6. Location of Section 5 and mussel survey transects in Middle Ditch, Big Lake National Wildlife Refuge, 2017.

Figure 7. Location of Section 6 and mussel survey transects in Middle Ditch, Big Lake National Wildlife Refuge, 2017.

Survey Approach

We surveyed approximately 9.4 km of Middle Ditch by searching bank to bank transects aligned perpendicular to flow. We spaced linear transects approximately 50 m apart in Sections 1 – 3 and 5 – 6 and measured width of wetted channel by stretching a weighted rope across it at each location. Using 1 m2 quadrats, two divers worked from the water’s edge towards the center of the channel to quantitatively sample each transect. Beginning at the upstream limit of the study area and extending to the uppermost margin of Big Lake, we numbered transect 1 to 159. We hand searched quadrats and then flipped them successively across the channel until they reached the opposite diver near the center of the channel (Figure 8). This method enabled us to quantitatively sample approximately 2% of the wetted area of Middle Ditch and qualitatively sample all available suitable habitat in Section 4. Our survey represents the first quantitative mussel data for Middle Ditch.

Wetted Width

1 m

Figure 8. Transect diagram. Mid line of each 1 m2 quadrat represents transect line positioned perpendicular to flow extending across wetted width of channel.

We sampled these sections from August 14 – September 20, 2017. Within each quadrat, we collected mussels by excavating the substrate to a depth of approximately 10 cm. Each diver identified, counted, and reported mussels to a tender/boat operator, who recorded all data via a diver to tender, diver to diver three-way underwater communication system. Nomenclature followed Williams et al. (2017). We calculated population estimates for each species and assemblage total community numeric standing crop using modified methods from Sampford (1962) (Huebner et al. 1990 and Harris et al. 1993) where total number of mussels were calculated as follows:

= 𝑖𝑖

𝑋𝑋 � 𝑦𝑦𝑖𝑖 𝑥𝑥 𝑔𝑔𝑖𝑖 Where X is total number of mussels in a bed, i is𝑜𝑜 the number of strata, yi is the sample total (total number of organisms encountered in the ni sampling units) and gi is the raising factor (gi = 1/fi,) where fi is the fraction sampled and is defined by ni/Ni, with ni being the number of sample

units counted in the ith stratum, and Ni the total potential number of sampling units in the ith stratum (Huebner et al. 1990). The 95% confidence interval around the total number of mussels in a mussel bed was calculated using the following formula:

X ± 𝑖𝑖 𝑖𝑖 2 2 1−𝑓𝑓 0 𝑖𝑖 𝑖𝑖 2 �𝑡𝑡 𝑥𝑥 �∑ 𝑁𝑁 𝑥𝑥 𝑆𝑆 𝑦𝑦 𝑥𝑥 𝑛𝑛𝑖𝑖 � Where S yi is the sample variance computed from raw counts in the ni sampling units in the ith stratum and t is the Student’s t for effective degrees of freedom (Huebner et al. 1990). We estimated relative error of our sample size and determined mean species density and number of quadrat samples required to estimate mean species density with 95 percent confidence limits (Southwood 1978) as follows: n = (s + (Ex))2

where: n = sample size (number of quadrats to sample) s = standard deviation of mussel density E = predetermined standard error as a decimal x = mean mussel density

RESULTS We collected data from 151 transects and 3,033 quadrats (Table 1). Transect location, width (=number of quadrats per transect), approximate depth, section number, and survey date are summarized in Appendix A. Our sample consisted of a total of 5,480 mussels, representing 17 species (Table 2). In addition, we collected numerous fresh, dead Fawnsfoot (Truncilla donaciformis) in Section 5 at multiple transects. Threeridge (Amblema plicata) was the dominant species in all sections. Bleufer (Potamilus purpuratus) was the second most dominant species overall in Sections 1 and 4 – 6. Wartyback (Cyclonaias nodulata) was the second most common species in Sections 2 and 3. We did not collect any Fat Pocketbook. Mean mussel density was similar in Sections 1 and 2 (0.4 and 0.7 mussels/m2, respectively) and in Sections 3 and 4 (1.2 and 1.7 mussels/m2, respectively) and greatest in Section 6 (3.4 mussels/m2). The number of quadrats yielding no mussels was greatest in Sections 1 and 2. In Section 1, mussel density ranged from 0 – 10 mussels/m2. However, Transects 1 – 3 of this section, which were located nearest to the water control structures, had the greatest mussel density (0 – 10 mussels/m2). Transects 4-26 in Section 1 had 0 – 3 mussels/m2.

Table 1. Summary of sections and sample effort for 2017 Middle Ditch mussel survey Variable Section 1 Section 2 Section 3 Section 41 Section 5 Section 6 TOTAL Transects Sampled 26 27 25 NA 30 43 151 Quadrats Sampled 586 623 162 NA 684 982 3,033 Estimated Length 1,461 m 1,179 m 1,179 m 1,345 m 1,581 m 2,618 m 9,364 m Mean Width 22.5 m 23.1 m 6.4 m NA 22.8 m 22.8 m 20.5 m Estimated Total Area 32,872 m2 27,235 m2 7,546 m2 NA 36,047 m2 59,690 m2 163,390 m2 1Section 4 was not accessible via boat and was qualitatively sampled where mussels were observed.

Table 2. Number of individuals, relative abundance, and population estimates for species by Middle Ditch section, 2017. Section 1 Section 2 Section 3 Section 4 Species Number (% Population Number (% Population Number (% Population Number (% Population of Section) Estimate of Section) Estimate of Section) Estimate of Section) Estimate Amblema plicata 101 (39.9) 5,666 ± 1,234 215 (52.8) 9,399 ± 3,294 88 (44.0) 4,099 ± 1,394 86 (55.1) NA Arcidens confragosus 3 (1.2) 168 ± 165 0 0 0 0 0 NA Fusconaia flava 1 (0.4) 56 ± 95 2 (0.5) 87 ± 105 0 0 1 (0.6) NA Lampsilis cardium 0 0 6 (1.5) 262 ± 234 2 (1.0) 93 ± 112 0 NA Lampsilis teres 15 (5.9) 841 ± 433 19 (4.7) 831 ± 435 20 (10.0) 932 ± 401 5 (3.2) NA Lasmigona complanata 9 (3.6) 505 ± 314 6 (1.5) 262 ± 234 0 0 3 (1.9) NA Leptodea fragilis 2 (0.8) 112 ± 135 1 (0.2) 44 ± 74 5 (2.5) 233 ± 175 9 (5.8) NA Obliquaria reflexa 18 (7.1) 1,010 ± 583 13 (3.2) 568 ± 264 4 (2.0) 186 ± 157 3 (1.9) NA Potamilus ohiensis 1 (0.4) 56 ± 95 0 0 4 (2.0) 186 ± 157 2 (1.3) NA Potamilus purpuratus 40 (15.8) 2,244 ± 682 37 (9.1) 1,617 ± 559 26 (13.0) 1,211 ± 526 22 (14.1) NA Pyganodon grandis 1 (0.4) 56 ± 95 0 0 1 (0.5) 47 ± 79 12 (7.7) NA Cyclonaias nodulata 28 (11.1) 1,571 ± 651 69 (17.4) 3,016 ± 789 32 (16.0) 1,490 ± 461 2 (1.3) NA Cyclonaias pustulosa 8 (3.2) 449 ± 300 20 (4.9) 874 ± 358 11 (5.5) 512 ± 278 9 (5.8) NA Quadrula quadrula 26 (10.3) 1,458 ± 512 18 (4.2) 787 ±327 6 (3.0) 279 ± 221 0 NA Tritogonia verrucosa 0 0 2 (0.5) 87 ± 105 0 0 2 (1.3) NA Toxomlasma texasiense 0 0 0 0 0 0 0 NA Utterbackia imbecillis 0 0 0 0 1 (0.5) 47 ± 79 0 NA COMMUNITY TOTAL 253 (100.0) 14,192±2,517 408 (100.0) 17,836±4,045 200 (100.0) 9,316 ± 1,998 156 (100.0) NA

Table 2 (continued). Number of individuals, relative abundance, and population estimates for species by Middle Ditch section, 2017.

Section 5 Section 6 Overall Total Species Number (% Population Number (% of Population Number (% Total) of Section) Estimate Section) Estimate Amblema plicata 777 (68.2) 40,948 ± 4,117 2,736 (82.3) 166,305 ± 16,363 4,002 (73.0) Arcidens confragosus 2 (0.2) 105 ± 126 5 (0.2) 304 ± 230 10 (0.2) Fusconaia flava 1 (0.1) 53 ± 89 1 (0.0) 61 ± 103 6 (0.1) Lampsilis cardium 0 0 2 (0.1) 122 ± 146 10 (0.2) Lampsilis teres 41 (3.6) 2,161 ± 982 115 (3.5) 6,990 ± 1,328 215 (4.0) Lasmigona complanata 16 (1.4) 843 ± 354 50 (1.5) 3,039 ± 711 84 (1.5) Leptodea fragilis 10 (0.9) 527 ± 333 28 (0.8) 1,702 ± 595 55 (0.9) Obliquaria reflexa 20 (1.8) 1,054 ± 433 10 (0.3) 608 ± 325 68 (1.2) Potamilus ohiensis 32 (2.8) 1,686 ± 510 5 (0.2) 304 ± 230 44 (0.8) Potamilus purpuratus 92 (8.1) 4,848 ± 875 145 (4.4) 8,814 ± 1,336 362 (6.5) Pyganodon grandis 73 (6.4) 3,847 ± 786 64 (1.9) 3,890 ± 825 151 (2.8) Quadrula nodulata 21 (1.8) 1,107 ± 476 22 (0.7) 1,337 ± 521 174 (3.3) Quadrula pustulosa 19 (1.7) 1,001 ± 405 85 (2.6) 5,167 ± 1,129 152 (2.7) Quadrula quadrula 28 (2.5) 1,475 ± 513 48 (1.4) 2,918 ± 797 126 (2.4) Tritogonia verrucosa 1 (0.1) 53 ± 89 3 (0.1) 182 ± 179 8 (0.1) Toxomlasma texasense 7 (0.6) 369 ± 235 1 (0.0) 61 ± 103 8 (0.2) Utterbackia imbecillis 0 0 3 (0.1) 182 ± 179 4 (0.1) TOTAL 1,140 (100.0) 60,078 ± 4,838 3,323 (100.0) 201,986 ± 17,757 5,480 (100.0)

Similarly, mussel density was low in the upper two-thirds (Transects 27 – 45) of Section 2, ranging from 0 – 4 mussels/m2. From Transect 46 – 53, we were able to wade the width of the channel. At this point, mussel density increased and number of transects with no mussels decreased. Mussel density ranged from 0 – 28 mussels/m2 for Transects 46 – 53 of this section. In Section 3, mussel density was ≤ 8 mussels/m2, with the exception of Transect 72 where one quadrat contained 15 mussels. We did not collect any mussel density data for Section 4 (qualitatively sampled). Mussel density in Section 5 ranged from 0 – 15 mussels/m2, but generally was ≤ 5 mussels/m2. The greatest density of mussels occurred in Transect 122 of Section 6 with 58 mussels/m2; similar densities of mussels also occurred in Transects 123 – 128 of this section. Excluding these seven transects, mussel density in Section 6 ranged from 0 – 22 mussels/m2. In Table 2, we summarized data by section, including population estimates and 95% confidence limits for each species. These data suggest that reproduction and recruitment are occurring for most species encountered in the study area due to presence of individuals in the 1 – 5 age cohorts, especially Threeridge, Wartyback, Giant Floater (Pyganodon grandis), Bleufer, and Threehorn Wartyback (Obliquaria reflexa).

DISCUSSION All species documented during this study are commonly found throughout the St. Francis River basin, particularly within the network of ditches. Species richness was greatest in Section 6 (N = 17), but similar across all sections. Pistolgrip (Tritogonia verrucosa), Texas Lilliput (Toxolasma texasiense), Paper Pondshell (Utterbackia imbecillis), Wabash Pigtoe (Fusconaia flava), and Fawnsfoot were the least frequent species collected and accounted for the greatest variation in species composition among the five quantitatively sampled sections. Sections 1 and 2 had the largest area of unsuitable substrate for mussel colonization, which explains the low mussel density found in these sections. Substrate in Section 1 consisted of “hard pan” clay across many transects except for narrow strips of clay with silt substrate near the transect termini, particularly in the middle and lower extents of the section. Section 2 was substantially deeper than other sections. Suitable habitat was limited to areas on descending banks that were not exposed to loose flocculent silt accumulations present in the thalweg. Mussels in Section 3 and 4 were restricted to perennially wetted areas not prone to channel drying during low flow periods and drawdowns. Therefore, available habitat was more limited by water levels than by substrate composition in Section 3 and 4. The width of wetted channel remained relatively unchanged during low flow periods in Sections 5 and 6. Anecdotal observations suggest that Sections 5 and 6 also have greater diversity of aquatic habitat (e.g., woody debris, sawgrass, bays, side channels, and closer proximity to Big Lake) for host fish. Therefore, greater mussel densities in these sections may be attributed to more diverse and stable habitat for both mussels and host fish.

Since the early 1900’s, BLNWR has been affected by various drainage and flood control projects. The large levee on the west boundary was built around 1900 by the St. Francis Levee District to confine flood waters to Big Lake and Little River. In the early 1920’s, drainage interests dug a 30-m wide ditch along the east boundary from the Missouri-Arkansas state line to Arkansas Highway 18 and constructed a levee from spoil material. The purpose of the project was to speed drainage from Missouri around Big Lake and confine overflow to Big Lake. During the early 1930’s, the Corps constructed man-made structures at Big Lake to substitute for the natural dam that was failing due to halted accretion of sediment associated with flood control in the area (U.S. Fish and Wildlife Service 1976). The lake level is essentially the same today as it was hundreds of years ago. The absence of Fat Pocketbook from Middle Ditch and its rarity in Ditch No. 81 upstream of the water control structure at Arkansas Highway 18 is perplexing. Substrate appears to be similar to substrate in nearby Stateline Ditch, which supports a large Fat Pocketbook population but has no water control structures. Similar habitat based on the author’s personal observations seems to exclude habitat availability as a possible explanation for Fat Pocketbook absence or rarity in Ditch No. 81 and Middle Ditch. According to BLNWR staff, the fish host for Fat Pocketbook (freshwater drum, Aplodinotus grunniens) inhabits the refuge’s ditches and Big Lake, but distribution, abundance, and seasonality data for drum are lacking. It is plausible that the water control structures on Ditch No. 81, Middle Ditch, and Big Lake prevent or greatly limit upstream/downstream movement of drum, thereby reducing drum abundance, particularly during spring spawning, which may coincide with Fat Pocketbook conglutinate (glochidia or larvae) release. Fish inventories targeting freshwater drum upstream and downstream of the water control structures at BLNWR and at selected locations in Stateline Ditch may explain why a large Fat Pocketbook population exists in Stateline Ditch, but is absent to rare in adjacent areas with similar habitat on the refuge. BLNWR substantially lowered water levels for water control structure maintenance in early August extending through the week of August 14. The drawdown left numerous mussels in Section 3 near the margins of the normal wetted channel and on high spots exposed to desiccation. We relocated many of these mussels to wetted areas to minimize mortality following transect sampling. A large concentration of mussels also occurred between the water control structures on Middle Ditch (Section 1) and Ditch No. 1, which was difficult to access due to concrete walls with no ladder access to the bottom. A large number of these animals, which appeared to be predominately Bluefers, located between the structures also were exposed to desiccation and perished.

MANAGEMENT CONSIDERATIONS AND MONITORING RECOMMENDATIONS

Protection or improvements in the status of mussels at BLNWR requires proper management of the watershed, lake, water control structures and cooperative efforts of stakeholders. The following management and monitoring recommendations are provided to assist with future refuge management.

Mussels are dependent on host fish, any effects of hydrological alteration on host fish also affects mussel populations. Short-term brooders spawn, brood, and release glochidia over a 2 – 6 week time period in spring/summer, while long-term brooders spawn in late summer/fall, brood eggs over winter and release glochidia in the spring/summer. Fat Pocketbook is a long-term brooder with spawning generally occurring in late August – September. Fertilized eggs are stored in the female until glochidia are fully developed and then released into the water in June – July. Therefore, seasonal discharge and water control structure design may affect distribution, abundance, and movement of freshwater drum, which in turn may reduce Fat Pocketbook distribution and abundance. We acknowledge water quality or other unknown factors also may be limiting Fat Pocketbook distribution and abundance. Because the water control structures present a plausible explanation, further investigation of freshwater drum presence/absence upstream and downstream of the water control structures and movement patterns (upstream and downstream) through the structures at varying flow rates are necessary. Depending on the results, alterations to the water control structures or changes to flow through the structures may be necessary to optimize Fat Pocketbook dispersal and recruitment in Middle Ditch and Ditch No. 81.

I recommend a baseline fish inventory in Middle Ditch, Ditch No. 81 (upstream and downstream of water control structures), and Stateline Ditch that emphasizes detection of freshwater drum. Monitoring the distribution and abundance of mussels in Middle Ditch is not necessary unless there is reason to document mussel response (e.g., Fat Pocketbook) to improved habitat or host fish availability. More frequent monitoring may be necessary to evaluate changes in mussel distribution, abundance, and recruitment to reduce uncertainties about how mussels respond to changing flow conditions or other management considerations.

We observed substantial mussel die-offs during this survey associated with refuge water level management in Middle Ditch for water control structure maintenance. I believe die-off events can easily be avoided by implementing the following recommendations:

1. Install a gage height marker on the water control structure(s). 2. Identify minimum gage height necessary to maintain normal wetted channel(s) without subjecting mussels to channel drying and desiccation. 3. Maintain a log book of how various gate openings/closings of each water control structure affect water levels. This information is necessary to make informed decisions regarding water levels and to prevent unnecessary mussel die-offs. 4. If water levels must be lowered below levels necessary to prevent subjecting mussel’s to channel drying, limit event duration to ≤5 days during cooler seasons and ≤3 days during hot weather (daytime highs exceeding 85° F). Raise water levels for a minimum 48 hours (e.g., weekend) prior to lowering again. This strategy is not preferable for normal water management and will likely stress mussels, but may minimize mussel mortality in rare instances when extremely low water levels are necessary (e.g., water control structure maintenance).

Identifying other important factors affecting mussel dispersal, spatial distribution patterns, and genetic connectivity at BLNWR also may be necessary. While the refuge has limited ability to influence the quality of water entering BLNWR, best management practices to reduce pollutant runoff/discharge from a variety of land use, municipal, and industrial activities will further improve water quality and habitat for mussels inhabiting BLNWR. Execution of these management considerations and strategies should

13 improve and/or sustain the quality and quantity of vegetative cover in riparian areas, decrease siltation and other chemical pollutants, provide environmental flows that promote mussel recruitment and survival and subsequently improve habitat quality.

ACKNOWLEDGEMENTS

I thank T. Inebnit, A. Bangs, S. Rimer, G. Graves, G. Webber, V. Ortiz, and G. French for their assistance in the field and shop. Completion of this project within budget and time constraints would not have been possible without their dedication and perseverance. This project was funded by the Service’s Southeast Region Inventory and Monitoring Network in partnership with BLNWR and the Arkansas Ecological Services Field Office. S. Rimer, R. Peak and T. Fotinos provided peer review of this report.

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Williams, J.D., A.E. Bogan, R.S. Butler, K.S. Cummings, J.T. Garner, J.L. Harris, N.A. Johnson, and G.T. Thomas. 2017. A revised list of the freshwater mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada. Freshwater Mollusk Biology and Conservation 20:33-58.

APPENDIX A

Appendix A. Location, survey date, presence/absence of mussels, number of quadrats per transect, and approximate thalweg depth for quantitative mussel survey transects in Middle Ditch, Mississippi County, Arkansas. Transect Live # of Thalweg Section Latitude Longitude Survey Date # Mussels Quadrats Depth (ft) 1 1 35.99169 -90.12037 8/14/2017 Yes 27 1-3 2 1 35.99095 -90.12047 8/14/2017 Yes 12 1-3 3 1 35.99042 -90.12032 8/14/2017 Yes 20 1-3 4 1 35.98983 -90.12009 8/14/2017 Yes 15 1-3 5 1 35.98940 -90.11982 9/12/2017 Yes 24 8-10 6 1 35.98897 -90.11953 9/12/2017 Yes 23 8-10 7 1 35.98853 -90.11908 9/12/2017 Yes 24 8-10 8 1 35.98811 -90.11872 9/12/2017 Yes 27 8-10 9 1 35.98776 -90.11830 9/12/2017 Yes 25 8-10 10 1 35.98749 -90.11790 9/12/2017 Yes 27 8-10 11 1 35.98694 -90.11790 9/12/2017 Yes 24 8-10 12 1 35.98650 -90.11826 8/14/2017 Yes 19 4-7 13 1 35.98612 -90.11853 8/14/2017 Yes 23 4-7 14 1 35.98566 -90.1188 8/14/2017 No 19 4-7 15 1 35.98526 -90.11917 8/14/2017 Yes 24 4-7 16 1 35.98486 -90.11939 8/14/2017 Yes 17 4-7 17 1 35.98442 -90.11945 9/11/2017 Yes 23 8-10 18 1 35.98384 -90.11928 8/14/2017 Yes 21 4-7 19 1 35.98343 -90.11915 9/11/2017 Yes 27 8-10 20 1 35.98289 -90.11922 9/11/2017 Yes 23 8-10 21 1 35.98243 -90.11924 9/11/2017 Yes 25 8-10 22 1 35.98198 -90.11940 9/11/2017 Yes 24 8-10 23 1 35.98145 -90.11947 9/11/2017 Yes 32 8 24 1 35.98107 -90.11952 8/14/2017 Yes 20 4-7 25 1 35.98053 -90.11952 8/14/2017 Yes 19 4-7 26 1 35.98011 -90.11952 8/14/2017 Yes 22 4-7 27 2 35.97974 -90.11963 9/11/2017 Yes 33 8-10 28 2 35.97931 -90.12000 8/17/2017 Yes 26 10-15 29 2 35.97894 -90.12032 8/17/2017 No 26 10-15 30 2 35.97855 -90.12056 8/17/2017 Yes 28 10-15 31 2 35.97818 -90.12086 8/17/2017 Yes 19 10-15 32 2 35.97783 -90.12118 8/17/2017 Yes 31 10-15 33 2 35.97746 -90.12151 8/17/2017 Yes 29 10-15 34 2 35.97729 -90.12180 8/17/2017 Yes 24 10-15 35 2 35.97703 -90.12220 8/17/2017 Yes 24 10-15

A-1

Appendix A. Location, survey date, presence/absence of mussels, number of quadrats per transect, and approximate thalweg depth for quantitative mussel survey transects in Middle Ditch, Mississippi County, Arkansas. Transect Live # of Thalweg Section Latitude Longitude Survey Date # Mussels Quadrats Depth (ft) 36 2 35.97665 -90.12238 8/17/2017 Yes 28 10-15 37 2 35.97631 -90.12260 8/17/2017 Yes 27 10-15 38 2 35.97592 -90.12265 8/17/2017 Yes 31 10-15 39 2 35.97560 -90.12293 8/16/2017 Yes 23 10-15 40 2 35.97527 -90.12335 8/16/2017 No 22 10-15 41 2 35.97498 -90.12360 8/16/2017 No 22 10-15 42 2 35.97468 -90.12399 8/16/2017 Yes 24 1-4 43 2 35.97433 -90.12434 8/16/2017 Yes 26 1-4 44 2 35.97397 -90.12456 8/16/2017 Yes 17 1-4 45 2 35.97360 -90.12482 8/16/2017 Yes 19 1-4 46 2 35.97328 -90.12523 8/16/2017 Yes 22 1-4 47 2 35.97298 -90.12545 8/16/2017 Yes 22 1-4 48 2 35.97268 -90.12567 8/16/2017 Yes 19 1-4 49 2 35.97241 -90.12608 8/16/2017 Yes 20 1-4 50 2 35.97200 -90.12635 8/16/2017 Yes 15 1-4 51 2 35.97167 -90.12639 8/16/2017 Yes 17 1-4 52 2 35.97124 -90.12633 8/16/2017 Yes 18 1-4 53 2 35.97091 -90.12651 8/16/2017 Yes 11 1-4 54 3 35.97053 -90.12649 8/15/2017 Yes 12 1-3 55 3 35.97013 -90.12646 8/15/2017 Yes 7 1-3 56 3 35.96972 -90.12672 8/15/2017 Yes 8 1-3 57 3 35.96954 -90.12717 8/15/2017 Yes 10 1-3 58 3 35.96936 -90.12762 8/15/2017 Yes 8 1-3 59 3 35.96891 -90.12801 8/15/2017 Yes 7 1-3 60 3 35.96851 -90.12825 8/15/2017 Yes 1 1-3 61 3 35.96797 -90.12841 8/15/2017 Yes 7 1-3 62 3 35.96743 -90.12853 8/15/2017 Yes 5 1-3 63 3 35.96699 -90.12866 8/15/2017 Yes 9 1-3 64 3 35.96665 -90.12837 8/15/2017 Yes 9 1-3 65 3 35.96627 -90.12811 8/15/2017 No 0 1-3 66 3 35.96589 -90.12783 8/15/2017 No 0 1-3 67 3 35.96543 -90.12763 8/15/2017 Yes 1 1-3 68 3 35.96503 -90.12753 8/15/2017 Yes 9 1-3 69 3 35.96469 -90.12738 8/15/2017 No 4 1-3 70 3 35.96412 -90.12756 8/15/2017 Yes 8 1-3 71 3 35.96372 -90.12788 8/15/2017 Yes 12 1-3 72 3 35.96348 -90.12835 8/15/2017 Yes 13 1-3

A-2

Appendix A. Location, survey date, presence/absence of mussels, number of quadrats per transect, and approximate thalweg depth for quantitative mussel survey transects in Middle Ditch, Mississippi County, Arkansas. Transect Live # of Thalweg Section Latitude Longitude Survey Date # Mussels Quadrats Depth (ft) 73 3 35.96334 -90.12875 8/15/2017 Yes 15 1-3 74 3 35.96343 -90.12934 8/15/2017 Yes 9 1-3 75 3 35.96351 -90.12982 8/15/2017 No 0 1-3 76 3 35.96332 -90.13025 8/15/2017 Yes 1 1-3 77 3 35.96316 -90.13057 8/15/2017 No 4 1-3 78 3 35.96291 -90.13067 8/15/2017 No 3 1-3 80 5 35.95458 -90.13295 9/19/2017 Yes 30 2 81 5 35.95405 -90.13314 9/19/2017 Yes 48 2 82 5 35.95385 -90.13397 9/19/2017 Yes 31 2 83 5 35.95351 -90.13448 9/19/2017 Yes 34 2 84 5 35.95295 -90.13505 9/19/2017 Yes 32 3 85 5 35.95251 -90.13533 9/19/2017 Yes 20 4-6 86 5 35.95200 -90.13567 9/19/2017 Yes 20 4-6 87 5 35.95153 -90.13565 9/19/2017 Yes 12 4-6 88 5 35.95111 -90.13544 9/19/2017 Yes 12 4-6 89 5 35.95076 -90.13508 9/19/2017 Yes 17 6-8 90 5 35.95040 -90.13471 9/19/2017 Yes 13 6-8 91 5 35.95023 -90.13423 9/19/2017 Yes 9 6-8 92 5 35.95028 -90.13369 9/19/2017 Yes 13 6-8 93 5 35.95045 -90.1331 9/19/2017 Yes 16 6-8 94 5 35.95058 -90.13239 9/19/2017 Yes 13 4-6 95 5 35.95065 -90.13185 9/19/2017 Yes 13 4-6 96 5 35.95050 -90.13137 9/19/2017 Yes 13 4-6 97 5 35.95008 -90.13151 9/19/2017 Yes 8 2-4 98 5 35.94966 -90.13152 9/19/2017 Yes 15 2-4 99 5 35.94926 -90.13152 9/19/2017 Yes 12 2-4 100 5 35.94872 -90.13156 9/20/2017 Yes 37 3 101 5 35.9481 -90.13165 9/20/2017 Yes 37 4-6 102 5 35.94768 -90.13192 9/20/2017 Yes 29 4-6 103 5 35.94710 -90.13193 9/20/2017 Yes 32 4-6 104 5 35.94671 -90.13234 9/20/2017 Yes 30 6-8 105 5 35.94624 -90.13252 9/20/2017 Yes 24 6-8 106 5 35.94576 -90.13247 9/20/2017 Yes 32 6-8 107 5 35.94538 -90.13215 9/20/2017 Yes 24 4 108 5 35.94504 -90.13188 9/20/2017 Yes 36 8-10 109 5 35.94470 -90.13148 9/20/2017 Yes 22 10-12 110 6 35.94396 -90.13063 NC NC NC NC

A-3

Appendix A. Location, survey date, presence/absence of mussels, number of quadrats per transect, and approximate thalweg depth for quantitative mussel survey transects in Middle Ditch, Mississippi County, Arkansas. Transect Live # of Thalweg Section Latitude Longitude Survey Date # Mussels Quadrats Depth (ft) 111 6 35.94358 -90.13071 NC NC NC NC 112 6 35.94317 -90.13067 9/20/2017 Yes 23 10-12 113 6 35.94277 -90.13064 9/20/2017 Yes 26 10-12 114 6 35.94234 -90.13063 9/20/2017 Yes 29 8-10 115 6 35.94189 -90.13076 9/18/2017 Yes 26 3-5 116 6 35.94142 -90.13099 9/18/2017 Yes 23 3-5 117 6 35.94104 -90.13130 9/18/2017 Yes 25 3-5 118 6 35.94063 -90.13164 9/18/2017 Yes 20 3-5 119 6 35.94022 -90.13191 9/18/2017 Yes 18 3-5 120 6 35.93981 -90.13210 9/18/2017 Yes 14 3-5 121 6 35.93932 -90.13208 9/18/2017 Yes 15 3-5 122 6 35.93874 -90.13215 9/15/2017 Yes 19 4-6 123 6 35.93835 -90.13235 9/15/2017 Yes 16 4-6 124 6 35.93791 -90.13236 9/15/2017 Yes 17 4-6 125 6 35.93741 -90.13230 9/15/2017 Yes 15 4-6 126 6 35.93690 -90.13233 9/15/2017 Yes 17 4-6 127 6 35.93650 -90.13231 9/15/2017 Yes 17 4-6 128 6 35.93591 -90.13250 9/15/2017 Yes 16 4-6 129 6 35.93544 -90.13259 9/14/2017 Yes 17 6-10 130 6 35.93496 -90.13263 9/14/2017 Yes 15 6-10 131 6 35.93448 -90.13269 9/14/2017 Yes 16 6-10 132 6 35.93397 -90.13278 9/14/2017 Yes 15 6-10 133 6 35.93351 -90.13278 9/14/2017 Yes 18 6-10 134 6 35.93305 -90.13284 9/14/2017 Yes 19 6-10 135 6 35.93260 -90.13292 9/14/2017 Yes 23 6-10 136 6 35.93216 -90.13296 9/14/2017 Yes 25 6-10 137 6 35.93168 -90.13298 9/14/2017 Yes 25 6-10 138 6 35.93124 -90.13304 9/14/2017 Yes 23 6-10 139 6 35.93077 -90.13305 9/14/2017 Yes 26 6-10 140 6 35.93025 -90.13306 9/14/2017 Yes 26 6-10 141 6 35.92974 -90.13307 9/14/2017 Yes 31 6-10 142 6 35.92928 -90.13309 NC NC NC NC 143 6 35.92879 -90.13311 9/13/2017 Yes 32 6-10 144 6 35.92795 -90.13323 9/13/2017 Yes 27 6-10 145 6 35.92752 -90.13316 9/13/2017 Yes 31 6-10 146 6 35.92707 -90.13314 NC NC NC NC 147 6 35.92662 -90.13329 9/13/2017 Yes 24 6-10

A-4

A-5

Appendix B

Scientific-Common Mussel Name Crosswalk

Scientific Name Common Name Amblema plicata Threeridge Arcidens confragosus Rock Pocketbook Cyclonaias nodulata Wartyback Cyclonaias pustulosa Pimpleback Fusconaia flava Wabash Pigtoe Lampsilis cardium Plain Pocketbook Lampsilis teres Yellow Sandshell Lasmigona complanata White Heelsplitter Leptodea fragilis Fragile Papershell Obliquaria reflexa Threehorn Wartyback Potamilus capax Fat Pocketbook Potamilus ohiensis Pink Papershell Potamilus purpuratus Bleufer Pyganodon grandis Giant Floater Quadrula quadrula Mapleleaf Tritogonia verrucosa Pistolgrip Truncilla donaciformis Fawnsfoot Toxomlasma texasiense Texas Lilliput Utterbackia imbecillis Paper Pondshell

B-1