East Fork Crooked Creek IA 03-SKU-6268

This evaluated biological assessment was based on data collected in 2014 as part of the IDNR/SHL headwater stream sampling project.   A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2014 FIBI score was 32 (fair) and the BMIBI score was 51 (fair).   The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008.   The FIBI BIC for this ecoregion is 36 and the natural substrate BMIBI BIC for this ecoregion is 51.   Even though this site passed both the FIBI BIC (using the UAV of 7 points applied to single samples) and BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small presumed BWW1 (formally general use) stream and doesn’t fall in the calibrated watershed size.

Additionally, this stream segment’s fish community was sampled on July 25, 2013 as part of the IDNR Watershed Improvement and Water Monitoring sections’ fishkill follow up monitoring program.   Sampling methods described in IDNR’s fish kill follow-up protocol (Attachment 5 of Iowa’s 2014 assessment/listing methodology) were followed.   Approximately 585 feet of stream were sampled using a single pass with backpack electro fishing units.   Results of this sampling show that this stream supports approximately 4,300 fish per mile compared to the Level IV ecoregion 47f average of approximately 1,590 fish per mile; 100% of the expected fish taxa for this ecoregion were sampled.   The results from this follow-up sampling and comparison of these results to ecoregion averages suggest that the fish community of this stream segment is similar to or better than non-fishkill impacted streams.   Although the results of the fishkill follow-up sampling lack the scientific rigor to determine whether the designated aquatic life uses are “fully supported,” the results do indicate that the stream has recovered from 2008 fish kill event.