with a rich species assemblage including the federally 

 endangered Lampsilis higgirisi. 



During the present survey quantitative samples 

 were collected on three separate occasions at the upriver 

 end of Sylvan Slough between the Interstate-74 highway 

 bridge and the upriver tip of Arsenal Island (Figure 3, 

 Table A-1). The location for each collection period 

 differed slightly to prevent sampling on the same spot 

 more than once. Substrate consisted primarily of sand/silt 

 with small rock cobble and water depths ranged from 2 to 

 4 m (6 to 10 ft). During our sample collections we noted 

 extensive use of this area by recreation watercraft; on 

 weekends as many as fifteen boats were observed floating 

 or anchored within this small area of Sylvan Slough. 



(2) Case-IH (RM 488.5) : (Figure 4) - This site was 

 chosen as a commercially harvested bed. Interviews with 

 commercial musselors indicated this bed had been 

 extensively harvested in the 1970's but has received only 

 occasional commercial pressure in the past ten years. We 

 observed two commercial mussel boats operating in this 

 area during our summer 1994 collections. Quantitative 

 mussel collections were made at this site in 1985 and 

 1987 by the INKS (Blodgett and Sparks 1987a and 

 1987b). These previous surveys reported mussels 

 exceptionally abundant, the number of species 

 exceptionally rich, and the federally endangered Lampsilis 

 higginsi present. 



Quantitative samples were collected at this site in 

 July and August 1994 (Table A-1). The collection area 

 was adjacent to the main channel and 150 m out from the 

 Illinois shoreline. Triangulation to the site was 

 accomplished using a cement piling, boat ramp, and 

 cement water tower (Case-IH logo on side). The site was 

 located on a straight line between the boat ramp and 

 middle cement piling and directly out from the cement 

 water tower. The substrate consisted of extensive areas 

 of bedrock with intermittent areas of sand and rock 

 cobble. Water depths within the sampling area ranged 

 from 4 to 6 m (12 to 20 ft.). 



(3) Uliniwek: RM 492.4 (Figure 5) - This site was also 

 chosen as a commercially harvested bed. According to 

 local musselors, this particular area (1) had been one of 

 the more productive beds in Reach 15 in the late 1960's 

 and early 1970's, but was depleted of commercial-size 

 shells during the late 1970"s or eariy 1980's, (2) was no 

 longer of commercial importance and most experienced 

 musselors had moved on to more profitable beds, and (3) 

 occasional inexperienced musselors had been observed 

 working this area periodically in the past ten years. To 



our knowledge, this site has not been scientifically 

 delineated or quantitatively sampled previously. 



Quantitative samples were collected on four 

 occasions: June and August of 1994 and Jime and 

 September of 1995. In addition, 415 mussels were 

 collected qualitafively at this site on 1 December 1994 for 

 use in sediment toxicity tests (Stoekel et al. 1996). The 

 collection area was located approximately 1 rivermile 

 downriver from Lock and Dam 14 and from 30 to 50 m 

 offshore from Illmiwek State Park. Substrate was fairly 

 uniform, consisting primarily of sand with occasional 

 small rock cobble. Water depths ranged from 2 to 3 m (5 

 to 9 feet). 



Field procedures 



During four sampling periods between July 1994 

 and September 1995 we collected from 72 to 116 

 quantitative samples representing a total surface area of 18 

 to 34 m- at each of the three sites in Reach 15 (Table A- 

 1). Quantitative samples were collected using procedures 

 normally employed by the INHS River Research Lab 

 (Sparks and Blodgett 1983, Blodgett and Sparks 1987a & 

 1987b). Biologists using surface supplied diving 

 techniques removed all material from within 0.25-m- or 

 1-m- metal frames to a depth of 18 cm. Quantitative 

 samples were collected by either the transect method, 

 where the diver places a metal frame at 5-m intervals 

 along a 100-m transect line anchored to the substrate, or 

 by random placement, where the diver places a metal 

 frame at random intervals while moving upriver. Samples 

 were sent to the surface in separate nylon mesh bags and 

 rinsed with river water through a series of four sieve trays 

 (mesh apertures of 20, 10, 5, and 2 mm). Material 

 retained by each tray was carefully examined to remove 

 live and recently dead mussels. Mussels were classified 

 as recently dead using the following criteria: (1) if soft 

 parts were present, unable to close valves when prodded; 

 (2) if soft parts were absent, the periostracum was intact, 

 valves were firmly joined by the hinge ligament, and the 

 interior nacre was shiny and not the least bit chalky. Live 

 and recently dead mussels were identified to species 

 (Cummings and Mayer 1992) and morphological shell 

 measurements of length, width, and height (Stansbery 

 1961) were recorded to the nearest 0.01 mm using digital 

 calipers. Most of the mussels collected were returned to 

 the river; however, a subsample of at least 30 individuals 

 of the most common species was retained and frozen for 

 further analysis. Zebra mussels attached to unionids were 

 mdividually counted and measured (shell length). 



