The Brandon Road Lock and Dam (BRLD) location is currently a focal point for developing a barrier to prevent Bighead carp (Hypophthalmichthys nobilis) and Silver carp (H . molitrix), hereafter referred to as invasive carps, from entering Lake Michigan and the Great Lakes Basin. This location is being considered because it connects the Illinois River to the Chicago Area Waterway System (CAWS) and ultimately Lake Michigan. While the possible effect s of the proposed barrier on commercial and recreational navigation are being widely debated, the impact s of the barrier on millions of dollars in aquatic resource restoration projects and decades of management effort s are less thoroughly considered. In addition to blocking movements of invasive carps, any barrier will also potentially eliminate upriver connectivity that is important to a variety of native fishes and freshwater mussels (hereafter referred to as mussels). Based on surveys of native fishes, we know that fish distribution and species richness in the Illinois River are steadily improving. However, very little is known about how or when fish move between habitats, and to what degree any of these might have been utilizing the lock chamber at BRLD to move upriver. The development of an upstream fish barrier, impassable by either non - native or native fishes, has potential unintended consequences for population s of native fish. We summarize d long - term trends in aquatic resources to illustrate both what is known and what is uncertain about a barrier that interrupts upriver connectivity. This includes details about several potential impact s that were developed using the best and most comprehensive information collected by the IDNR - Division of Fisheries (IDNR - DF) , Illinois Natural History Survey (INHS) , and from the peer-reviewed literature. The summary focuses on long-term trends in species richness and presence or absence over time, found i n the neighboring tributary rivers including the Des Plaines River, DuPage River, Kankakee River, Fox River, and upper Illinois River. The primary impact of the proposed barrier project on native fish and mussel s is the blockage of upriver fish movement from the Illinois River and its tributaries, past BRLD into the Des Plaines River and CAWS. Improvements in aquatic habitat quality and connectivity through dam removals upstream of BRLD have, and will continue to open additional aquatic habitat. Long-term fish community surveys in the Des Plaines River suggest numerous species of fish currently pass through the lock at BRLD and that this helped some native fishes such as the pollution intolerant Rosyface shiner (Notropis rubellus) re-establish in these formerly degraded reaches after conditions improved (Pescitelli 2017). Despite a record of improvement (similar to fishes) over recent decades, mussel diversity and numbers are currently limited in the Des Plaines River above BRLD. Recruitment of these invertebrates requires both a source of young and fish-hosts to carry them into newly improved habitats. Data suggest that there is a source of young below BRLD: seventeen species of mussel s not currently present above BRLD have been documented just 21 kilometers or less below BRLD in the Dresden Pool of the upper Illinois River (an easily covered distance for fish). Thus, any reduction in upriver connectivity will be a threat to the ongoing improvement in both upstream fish and mussel populations. The extent to which the current fish community above BRLD relies on connectivity through the lock to maintain community stability is uncertain. Though it appears likely continued increases in species richness upriver of BRLD would be truncated after implementation of a barrier, further targeted investigations in to trends in recruitment, movement, and abundance may help guide choices of appropriate mitigation efforts. This information could also inform efforts to prioritize the management, translocation, or stocking used to supplement fish-hosts required for rehabilitation of mussels if a barrier is implemented at BRLD.
|Original language||English (US)|
|Place of Publication||Havana, IL|
|Publisher||Illinois Natural History Survey|
|Commissioning body||Illinois Department of Natural Resources, Division of Fisheries|
|Number of pages||49|
|State||Published - Sep 24 2018|
|Name||INHS Technical Report |