Survival and growth rates of juvenile salmonids reared in lowland streams

The aim of this study was to assess the efficiency of propagating juvenile trout, Salmo trutta L. in small lowland streams and to evaluate the impact of the environmental conditions in the streams on the juvenile fish. Brown trout (Salmo trutta fario) and sea trout (Salmo trutta trutta) early fry fed under controlled conditions were used to stock third-order lowland streams. During summer, fall, and spring catches, fry were counted, measured, and weighed. The following parameters were calculated using the data collected: fry stocking density (ind. m-2); survival; specific mortality rate (SMR); length range; mean specimen length; body weight; mean body weight; specific growth rate (SGR); body condition (Fulton’s index). The ichthyological studies were accompanied by simultaneous analyses of environmental conditions that were performed monthly, and benthic macroinvertebrates were sampled in spring and fall. No differences were observed in the biological parameters analyzed between sea trout and brown trout. Variability in environmental parameters such as temperature, oxygenation, conductivity, and stream width and depth were associated with differentiation in the biological parameters of the fry. The results clearly indicate that the considerable potential of small lowland streams for the propagation of salmonid juvenile stages is currently underexploited

Diversity of Fish and Zoobenthic Communities in Lowland River Related to the Factors of Hydromorphological, River Continuum and Pollution Disturbances

The response of zoobenthos and ichthyofauna to different levels of habitat degradation was estimated on a small lowland river. The level of fragmentation, the hydromorphological modifications of the watercourse bed, and the water quality of different river stretches were assessed as proxies of the degree of anthropogenic transformation of habitats. The degree of fauna similarity between the study sites, as well as the relationships between habitat quality and biotic indexes were estimated. A strong response of both assemblages to changes in environmental conditions was demonstrated, however, reaction to individual pressures differs. This confirms that these organisms are excellent, universal bioindicators and both groups should be used together. The key role of a well developed riparian zone in shaping the diversity of freshwater biota has also been demonstrated

Pro-ecological and conservation activities are not always beneficial to nature: a case study of two lowland streams in Central Europe

Abstract Since 1990 and in particular, after the implementation of the Water Frame Directive, many positive effects of pro-ecological projects are evident; unfortunately, examples of adverse effects have also been observed. This study aims to indicate how some ill-considered actions, called “pro-ecological”, may lead to habitat degradation and the disappearance of valuable hydrobiont species. Two watercourses, representing the lowland gravel stream and sandy stream type, were selected for the study. Literature indicated that in the past, these watercourses were characterized by an excellent ecological status and the presence of valuable rheophilic fauna and flora. Environmental parameters were recorded, macroinvertebrates and ichthyofauna were sampled and analyzed, and finally, indexes were calculated. The results were compared with literature data. In the course of studies conducted in 2011–2015, drastic habitat deterioration and extensive changes in the species structure of ichthyofauna and aquatic invertebrates were observed. Changes in the Smolnica stream have been caused by the three retention basins constructed in 2000, along the lower and middle course; while in Kiszewko, however, the factor for habitat deterioration was connected with the excessive expansion of the Eurasian beaver (Castor fiber), which created a beaver pond 20 m in width, with impoundment elevations of up to 2 m

Effects of eutrophication on vendace, Coregonus albula (L.). I. Limnological characteristics of selected lakes in Wielkopolska

Abstract. The aim of the study was to characterize the abiotic environmental factors influencing the occurrence and biology of vendace, Coregonus albula (L.). The analyses covered four lakes in the Wielkopolska region -lakes Dominickie, Gorzyñskie, Lubikowskie, and Strzeszyñskie. The most important natural characteristics of the lakes were analyzed, and their current trophic states were determined. Moreover, two trophic state indicators were also used -the HB index and the Carlson index. Parameters differentiating the lakes most strongly included area, depth, area-depth index, shoreline development, and fish yield index. In terms of morphometry, lakes Gorzyñskie and Lubikowskie are most suitable for optimal vendace fishery management. The least developed stratification was observed in Lake Dominickie, while the most marked stratification was noted in Lake Gorzyñskie, which had the shallowest epilimnion depth, the highest thermocline temperature gradient, and a deep, cool hypolimnion. Considerable deoxygenation was observed in the summer in the hypolimnions in all the lakes; however, oxygen deficits were also detected in the metalimnion of Lake Strzeszyñskie. Based of the analysis of physicochemical factors and trophic state indexes, good water quality was noted in all the analyzed lakes. The trophic state of Lake Gorzyñskie was designated as on the border between the mesoeutrophic and eutrophic states, while lakes Dominickie, Lubikowskie, and Strzeszyñskie were designated as eutrophic