Checking investigations of ichthyofauna, specifically non-indigenous species, are a significant component of research on oceanic biological systems. This data is fundamental for demonstrating populace development and anticipating paces of extension, quanti fying environmental effects and surveying the adequacy of evacuation and control procedures. All things considered, the most convincing fish intrusion in Polish freshwaters is seemingly the incidental presentation of the top mouth gudgeon (Pseudo-rasbora parva). Age and lengths structure, condition factor and development pace of the intrusive populaces of the top mouth gudgeon from little Polish waterways was inspected. The examples were gathered from the waterways: Molnica (n = 41), Myśla (n = 21) and Wardynka (n = 101) not long after the attack was recorded (2017). Assessed times of top mouth gudgeon ran from 1+ to 3+ for the Myśla River, from 1+ do 4+ for the Molnica River, and from 1+ to 5+ for the Wardynka River. The fish from the Molnica River was portrayed by the most reduced aggregate and standard length (TL, SL), weight, and most elevated condition. The re-sults of back-figuring’s and the parameters of von Bertalanffy’s development condition uncovered particular imbalances in the standard length (mm) in individual age gatherings (Molnica River: Lt = 54.94 [1 – e–0.68885 (1 – 0.003404)], Myśla River: Lt = 55.39 [1 – e–0.74921 (1 – 0.030962)], Wardynka River: Lt = 66.33 [1 – e–0.69348 (1 – 0.369505)]). The presentation of the top mouth gudgeon happened in the upper and medium divisions of little waterways, yet in consequent years the species moved to new locales further downstream and this may have influenced the local ichthyofauna.
fish, fish age, fish condition, fish development, intrusive species, Pseudo-rasbora parva, little waterway.
1. The presence of non-local animal groups is amazingly hard to assess for our assets of local ichthyofau-na. One of other obtrusive animal groups, which is topmouth gudgeon, showed up in the streams: Molnica, Myśla and Wardynka.
2. Tragically, they gradually started to settle in increasingly more Polish water supplies. Much of the time, top mouth gudgeon lives in lakes, however as of late likewise settled in little streams.
3. The top-mouth gudgeon is described by high natural resilience [GOZLAN et al. 2010], what was confirm by the physico-synthetic states of the tried streams.