In 2010 electrofishing was conducted at four sites located in the Ner River section flowing across the City of Łódź. Two species co-dominated in abundance: perch (36.1%) and roach (34.2%). The site downstream from the Stefańskiego Ponds was most abundant in fish. Among 13 species represented by almost 3 thousand specimens captured there perch and roach (36.9% and 32.6%, respectively) were dominants, while ruffe (16.5%) was a subdominant. The most human-impacted site was located downstream from the Dobrzynka Stream inflow, where no fish were caught. A comparison of the present state of fish fauna with that of monitoring studies carried out during the recent decade in the river’s section flowing across the City of Łódź indicated no significant changes in fish assemblage structure. The species composition and assemblage structure of the section is positively influenced by the recreational ponds, which feed their adjacent reaches of the river with fish. Unfortunately, in two of the sampling sites the situation of fish remains critical, which is testified to by almost total lack of them. The reason of this situation is low water quality and isolation (chemical barrier) of the upper Ner River system from the Warta River.
In the City of Łódź there are 29 streams and rivers of various sizes, 18 of them named and 11 unnamed, whose total length is 125 km. The aim of the present study was gaining initial knowledge of the abundance and diversity of aquatic macroinvertebrates in water courses in the City of Łódź. Collected aquatic macroinvertebrates were represented by 18 taxons. The highest occurrence was recorded for Dipterans (Chironomidae) (present in all samples), Oligochaeta, Ephemeroptera and Gastropoda. The distribution of macroinvertebrates along the investigated streams varied very much. The Jasień and Łódka Streams turned out least abundant and taxonomically diverse in macroinvertebrates. The opposite were the Bzura and Łagiewniczanka Streams. It confirmed that usually the differences in macroinvertebrate distribution and diversity resulted from pollution of the running waters with domestic and industrial sewage, transforming of certain water courses into sewage-storm canals, regulation including covering of river beds and banks with concrete.
In 2010 in the City of Łódź, Central Poland, electrofishing was carried out at 12 sites in the Miazga, Bzura, Sokołówka and Lagiewniczanka Streams in the Vistula system. Eight fish species were recorded, of which two were alien (giebel Carassius gibelio and topmouth gudgeon Pseudorasbora parva) and only two were rheophilic (ide Leuciscus idus and gudgeon Gobio gobio). Roach Rutilus rutilus and three-spined stickleback Gasterosteus aculeatus constituted 64% of all the fish in samples. Stone loach Barbatula barbatula, usually common in other similar streams, was absent. The fish distribution and abundance was significantly determined by the stream regulation. In the Sokołówka electrofishing was conducted earlier at the same six sites in 2002. Seven species were recorded in both terms; in 2010 ide (coming from stocking) was captured instead of the previously recorded crucian carp Carassius carassius. The total fish abundance was over twice lower than in 2002.
In 2010 in the City of Łódź, Central Poland, electrofishing was carried out at 15 sites in the Dobrzynka, Jasień, Olechówka, Łódka and Jasieniec Streams in the Ner/Odra system. Fourteen fish species were recorded (13 species in the Olechówka and altogether 7 species in the remaining streams), of which six were limnophilic and only two rheophilic. Sunbleak Leucaspius delineatus, gudgeon Gobio gobio and stoneloach Barbatula barbatula constituted 90% of all the fish in samples. Over 100 specimens were caught at each site in the Olechówka Stream, while only 1 -11 specimens were recorded at each of the remaining sites (except one fishless site in the Jasieniec Stream). The fish distribution was determined by water purity strongly connected with the type (combined/separate) of urban sewage system functioning in a given stream basin. The condition of ichthyofauna in 2010 was slightly better than during electrofishing conducted in 2001. The Jasień and Łódka Streams were fishless in 2001 while in 2010 several fish specimens at each site belonging to the total of 3 and 4 species, respectively were recorded. In the Olechówka, in 2010 five new species were caught and the total fish abundance was over 3 times higher than in 2001.
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