Assessment Comments
Assessment is based on the analysis of the lake's fish populations by the IDNR Fisheries Bureau in 2003.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses remain “not assessed” due to the lack of monitoring information upon which to base an assessment. The Class B(LW) aquatic life uses are assessed (monitored) as “partially supported” based on results of a sampling and analysis of this lake’s fish populations in 2003. The Class C (drinking water) uses are “not assessed” due to the lack of recent information upon which to base an assessment.
Note: A TMDL for siltation at Binder Lake was prepared by IDNR and approved by EPA in 2001; thus, this lake was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. Based on recent monitoring, the primary cause of impairments of impairments of the Class B(LW) uses of this lake is the impact of exotic species (common carp) and introduced species (yellow bass) on the fish populations of this lake. Thus, this waterbody was moved from IR Category 4a to Category 4c (impaired by non-pollutant stressor; TMDL not required) for the 2006 assessment/listing cycle. Binder Lake remains in IR Category 4c for the 2008 assessment/listing cycle.
EXPLANATION: The Class A1 (primary contact recreation) uses of this lake are “not assessed” due to the lack of water quality data or other information upon which to base an assessment. This lake is not part of the IDNR/ISU, 2000-2006 statewide survey of Iowa lakes. Nor has this lake been monitored as part of the IDNR/UHL ambient monitoring program.
The Class B(LW) uses of Binder Lake are assessed (monitored) as “partially supported” due to impacts of an exotic species (common carp) and a nuisance species (yellow bass) on the lake’s sport fish populations. The staff from the IDNR Fisheries Bureau sampled the fish population of Binder Lake on September 8, 10, and 17, 2003. Night electro-fishing was used on September 8 with daytime electrofishing and fyke nets on the 10th and 17th, respectively. Based on the analysis of the fish populations at this lake performed by IDNR Fisheries Biologists, (i.e., length/frequency analysis, growth rates (relative weight analysis), and population estimates), the fish population of Binder Lake appears to be below expectations, thus suggesting an impairment of the Class B(LW) aquatic life use. Comments from IDNR Biologists, based on their 2003 sampling and analysis, suggest that both common carp and yellow bass are adversely impacting the sport fish populations of Binder Lake. Turbidity caused by the feeding activities of common carp and by wave action is seen as hampering the sport fish population. The IDNR biologist stated that the mere presence of common carp in the sample is a negative indicator for the fishery. An additional factor affecting the fisheries this lake is the presence of yellow bass. Based on the results of the 2003 sampling, the yellow bass population of Binder Lake is quite dense. At high densities, yellow bass fail to grow to a harvestable size (stunting). In addition, yellow bass are known to feed on eggs and the larval stage of nest-building sport fish species such as bluegill and largemouth bass, thus suppressing reproduction of those species. Successive year classes of desirable sport fish species cannot reproduce at levels required to maintain their population. In the short-term, the growth rate of these sport fish species is good due to low densities. In the long-term, however, the impacts of yellow bass is typically a dramatic reduction or elimination of sport fish species and the lake’s sport fishery. According to IDNR's 2006 assessment/listing methodology, exotic species such as common carp or nuisance aquatic species such as yellow bass are considered "non-pollutant stressors". Impairments caused by non-pollutant stressors are appropriate for Category 4c of Iowa's Integrated Report.
The Class C (drinking water) uses are “not assessed” due to the lack of recent monitoring data upon which to base an assessment. In previous 305(b) assessment cycles, the Class C uses were assessed as "fully supported/threatened” (not impaired) based on results of sampling conducted by UHL in January 1995. These data, however, are greater than 10 years old and are thus considered too old to accurately characterize current water quality conditions.
