Baseline assessment and analysis of fish, macroinvertebrates and herpetofauna in the Otter Creek coal tracts area of Powder River County
By: prepared for: Pat Farmer, Project Manger/Director, Westech Environmental Services, Helena Field Office ; prepared by: David Stagliano, Aquatic Ecologist, Montana Natural Heritage Program
Contributors: Farmer, Pat; Montana Natural Heritage Program; Westech Environmental Services
Published: 2012
Language: eng
Number of pages: 30
Subjects: Fishes; Aquatic invertebrates; Reptiles; Amphibians; Aquatic ecology
Description: We summarize the first year of baseline surveys for the Aquatic Assessment of Fish,  Macroinvertebrates, and Herpetofauna in the Otter Creek coal tracts area. Project goals were: 1)  to conduct standardized surveys and collect baseline information on the aquatic and riparian  communities occurring in Otter Creek and three tributaries (seasonally and spatially oriented)  prior to coal development, 2) to assess aquatic community integrity and condition by interpreting  key indicators recorded at sites using standardized protocols and biotic thresholds, and to  compare these against reference condition standards. These data collected represent predevelopment  (i.e. pre-impact, BACI design) conditions at the local reach scale.  Habitat assessments, herpetofauna, macroinvertebrate and fish surveys were performed  seasonally at three predetermined mainstem Otter Creek reaches (control, impact and  downstream) and three tributaries coinciding with established surface water quality stations during  2011. Additionally, we added fish sampling visits to Otter Creek Impact #2 (upstream of the  Threemile Creek confluence) because Threemile Creek remained dry during all visits. In total,  we performed 15 surveys for fish during the visits: 11 at four mainstem Otter Creek reaches and  four surveys at two tributary streams. Fifteen macroinvertebrate samples were collected during  the visits; neither taxa survey was conducted at Threemile Creek in any season due to lack of  surface water present. All six a priori stream reaches were visually surveyed for amphibians or  reptiles during all visits. Biological community integrity was calculated for 15 fish surveys using  Fish Integrated Biotic Indices (IBIs) and Observed/Expected Models (O/E), while the 15  macroinvertebrate samples were assessed with Montana DEQs multimetric indices (MT MMI). Habitat Evaluations. Of the seven sampling reaches evaluated in the study area, we found three in Proper Functioning Condition (PFC) with a stable trend and four were Functional at Risk (FAR).  Reasons that sites ranked FAR were likely due to anthropogenic habitat alteration by cattle (Home  Creek {Otter_1A and Threemile Creek {Otter 3m}) or stream manipulation (Otter Creek JTTrussler  and Otter Creek #16). Highest site integrity scores using both the BLM Habitat and PFC  Assessment methods were recorded at the Otter Creek sites #23 (Tenmile Creek) and #22 (control-  Denson reach). Sites with lower habitat scores were structurally degraded predominately by cattle  use and had high associated Livestock Use Indices (LUI) (Home Creek, Threemile and Otter Creek  #16-fall). Point conductivity measurements recorded at all Otter Creek mainstem sites across  most seasons were above the threshold for impairment levels (>500us, DEQ 2006), and Home  Creek site 1A had visible signs of natural gas seepage from the sediments.  Macroinvertebrate Communities: Overall, 104 unique macroinvertebrate taxa were reported from  the 15 macroinvertebrate assessment samples. One known Montana species of concern (SOC),  the mayfly, Caenis youngi was collected in fair numbers at the control site, Otter Creek #22.  Average macroinvertebrate taxa richness per site was 29.5 and the highest taxa richness was 41  taxa reported at the Otter Creek JT site. Using the Montana DEQ macroinvertebrate multimetric  index (MMI), four of the five sites (12 of 15 samples) were ranked non-impaired (good to excellent  biological integrity), while all three samples from Tenmile Creek were ranked marginally impaired.  Stream sites that maintained flowing, connected water scored higher with the MMI than sites withinterrupted pool areas. Overall, mainstem sites evaluated in the Otter Creek study received  significantly higher macroinvertebrate MMI scores than those in the tributaries (T-test, p <0.01).  MMIs did not significantly differ on Otter Creek mainstem Pre-Impact Control, Impact or  Downstream Sites (T-test, p >0.05), despite the fish communities reflecting a decrease in biotic  integrity.  Fish Communities. Overall, nine fish species (five native/four introduced) were identified from  37,679 individuals collected from 15 site visits (Table 4). One potential species of concern (PSOC),  the brassy minnow, was collected at five of six sites. Average fish species per Otter Creek  mainstem site across all seasons was 6.5 (± 0.8 SE), while the tributary sites averaged 1.75 species  (Table 4). All fish presence sites also reported at least one species of amphibian. Lake chubs had  the highest site occupancy rate at 93% (14 of 15 visits) followed by fathead and brassy minnows at  80% (12 of 15 visits). Fish data collected in previous years from three sites within the study area  showed similar biological integrity over time. The most diverse site in the study area was Otter  Creek JT site with nine species, while the most intact sites were Otter Creek Site #22 at Densons  (four native) and the Tenmile Creek spring survey (two native spp.). Using Montanas Prairie Fish  IBI, 9 of the 15 fish sites were ranked non-impaired (good biological integrity), two were slightly  impaired (moderate integrity) and four were moderately impaired (poor biotic integrity). Fish IBIs  decreased going downstream on Otter Creek, and the Pre-Impact Control Site scored significantly  higher than Impact or Downstream sites (T-test, p <0.05).  Amphibian and Reptile Incidentals. Eight herpetofauna species were observed, collected in  dipnets/seines or incidentally recorded in conjunction with the fish, habitat and macroinvertebrate  surveys. We reported four amphibian species, of which, Woodhouses Toad (Bufo woodhousii)  had the highest site occupancy, occurring at six of seven sites, followed by the Northern Leopard  Frog (Rana pipiens) and Tiger Salamander (Ambystoma tigrinum) recorded at five and four sites,  respectively. Boreal Chorus Frog (Pseudacris maculata) was detected at three sites during the  spring visits only. We also recorded four reptile species (in order of site occurrence): Western  Rattlesnake (Crotalus viridis), Painted Turtle (Chrysemys picta), Terrestrial Garter Snake,  (Thamnophis elegans) and Snapping Turtle (Chelydra serpentine) (SOC).  Conclusions. The aquatic community sampling sites chosen for pre-impact baseline data were  representative of the range of stream classes found in the Otter Coal Tracts project area:  Ephemeral, Intermittent and Perennial Prairie Streams. Despite this having been an unusually high  water year for the region, stream communities that we sampled encompassed the range of  expected species to occur in these stream types. Biotic integrity of sites was initially higher in the  upstream control reaches of Otter Creek. One extraordinary finding was the high density and large  biomass of fish inhabiting the stream reach below Truslers Ranch road crossing (20,000 fish in  the 300 m reach fall survey, 15 fish/m2); this was most likely an artifact of the impassible culvert  located here and the fish stacking up downstream of this barrier. Density dependent fish  anomalies (lesions and parasites, i.e., yellow grub and anchorworm) were prevalent at this site,  indicating the fish were likely experiencing stress from overcrowding. Benthic macroinvertebrate  densities at this site were low, but, more diverse than other sites, indicating that the fish may have  been consuming large portions of the available insect production, having a topdown community  effect.
Notes: Cover title.

"January 2012"

Includes bibliographical references (pages 25-26).
Table of contents: title: Introduction; title: Methods; title: Results; title: Conclusions; title: Site Photos; title: Literature Cited; title: Appendix A. Fish data and IBI metric calculations collected from Otter Creek Project Sites; title: Appendix B. Macroinvertebrate taxa list, abundance, and metrics for the 15 collection sites.