| The Oriental Weatherloach Misgurnus anguillicaudatus is an East Asian benthic freshwater fish species that has been introduced into many freshwater systems outside its native range of Russia, Korea, China, Japan, Vietnam, and Burma (Keller and Lake 2007). Introductions were primarily associated with the pet trade, although other purposes were also important, such as human consumption and live bait (Keller 2000). Oriental Weatherloach were first recorded in the Chicago Area Waterway Systems (CAWS), Illinois in 1987; their most likely source of introduction was via the pet trade (Page and Laird 1993, Burr et al. 1996, Laird and Page 1996). Although populations have become established worldwide, little is known about the potential impacts of Oriental Weatherloach on native flora and fauna. This study was designed to examine the basic population demographics and feeding ecology of Oriental Weatherloach in northeastern Illinois and northwestern Indiana. Specifically, the project aimed to examine the reproductive development, age and growth relationships, and feeding habits of Oriental Weatherloach in the CAWS.;A variety of methods were used to collect 133 Oriental Weatherloach from the 2010, 2011, 2013, and 2014 field seasons; these methods included backpack and boat electroshocking, baited minnow traps, mini fyke nets, and impingement nets. The largest concentrations of fish were found in Cook and Will County, IL, specifically within the Des Plaines River, the Chicago Sanitary and Ship Canal (CSSC), and the Illinois and Michigan Canal (I & M Canal or IMC). Sampled fish were weighed and measured for total length and then dissected to examine the gonadal weight for reproductive stage, otoliths for aging, and gut contents for diet of each fish.;The mean length of Oriental Weatherloach was 125 mm for males and 150 mm for females. The gonadal somatic index (GSI) indicated an early spring spawning season, with a peak in gonadal weight for both sexes in April which drastically declined in May. Observation of the otoliths suggested that fish ranged in age from 0-3 years. Catch curves analysis (estimated mortality rate of the number of fish caught per age class) indicated that fish did not fully recruit to gear (were not large enough to be vulnerable to gear) until 2 years of age, and suggested that Oriental Weatherloach had an annual mortality rate of 88.5% and an annual survival rate of 11.5%; however, final conclusions on mortality/survivals rates cannot be determined at this time because only 2 age-classes were compared.;Of the stomach samples examined, 19% were empty and 81% contained particles (34% plant/sediment material and 66% actual prey items). Oriental Weatherloach fed mostly on benthic invertebrates, although tadpoles and fish eggs were also ingested. The Index of Relative Importance (IRI) analysis indicated a noticeable difference in the consumption of prey items during the months of May (Dragonfly Larva, Odonata), July (Nonbiting Midges, Chironomidae), and August (Fingernail Clams, Sphaeriidae). Diet breadth analysis also fluctuated throughout the field season, which suggests that Oriental Weatherloach were more of an opportunistic feeder with a fairly diverse diet.;Oriental Weatherloach are now a part of the fauna in the CAWS; populations are well-established and expected to expand. At some level, these fish are likely competing with native species for food and habitat resources. However, direct ecological impacts are still not known. This study stresses the need for further research to assess the possible ecological impacts caused by this invasive species. |
