Krzysztof Kukuła

Ichthyofauna of a mountain stream dammed by beaver

Ichthyofauna of a mountain stream dammed by beaver The aim of the study was to examine the impact of the European beaver, Castor fiber L., on the ichthyofauna of Negrylów Stream. Three study sites were designated in segments of the stream with running waters and two in beaver ponds. The waters at all the sites were characteristic of naturally polluted mountain streams. The occurrence of brown trout, Salmo trutta trutta m. fario L.; Siberian sculpin, Cottus poecilopus Heckel; common minnow, Phoxinus phoxinus (L.); and stone loach, Barbatula barbatula (L.), was confirmed. The highest density and abundance of brown trout was noted in the ponds, where the mean lengths and weights of brown trout were also the highest noted in the current study. Large trout occurred only in the ponds. In the shallow, running segments of the stream mostly brown trout fry were caught. Differences among fish assemblages in the segments of the stream and the ponds were statistically significant. After the introduction of the beavers, the state of the ichthyofauna in Negrylów Stream, which had suffered substantial degradation from forestry works, improved markedly. In comparison to analagous segments of other streams in the Bieszczady Mountains, fish density and biomass here were very high. Ichtiofauna potoku górskiego zabudowanego przez bobry Celem pracy było zbadanie wpływu bobra europejskiego, Castor fiber L. na ichtiofaunę potoku Negrylów. Badania prowadzono w latach 2007-2009 na 5 wyznaczonych stanowiskach. Przeprowadzono czterokrotne elektropołowy ryb i wykonano pomiary 19 parametrów fizyko-chemicznych wody. Dla wszystkich badanych parametrów wykazano brak istotnych statystycznie różnic pomiędzy średnimi wartościami. Stwierdzono cztery gatunki ryb: pstrąga potokowego, Salmo trutta trutta m. fario L., głowacza pręgopłetwego, Cottus poecilopus Heckel, strzebli potokowej, Phoxinus phoxinus (L.) i śliza, Barbatula barbatula (L.) Najwięcej ryb złowiono w dolnej części potoku a największą biomasę miały ryby złowione w stawach. Zagęszczenie, biomasa oraz średnia długość i masa pstrąga potokowego była największa w stawach bobrowych. Głowacz pręgopłetwy w stawach spotykany był rzadko, a strzebla potokowa występowała tylko w stawie głównym i w odcinku dolnym potoku, gdzie była bardzo liczna. Różnice pomiędzy zespołami ryb z odcinków płynących i stawów były istotne. Zbudowane przez bobry tamy przyczyniły się do powstania siedliska z głęboką, dobrze natlenioną, stojącą wodą. Ryby o długości całkowitej > 20 cm występowały prawie wyłącznie w stawach, gdzie głębsze miejsca, podmyte korze-nie i zatopione drzewa utworzyły liczne kryjówki. W płytkich, płynących odcinkach potoku dominowały stadia juwenalne o długości 6-11 cm (90%). Zmiany w korycie potoku wywołane działalnością bobrów wpłynęły na zespoły ryb. Stan ichtiofauny w zniszczonym wcześniej w wyniku prac leśnych potoku Negrylów po wprowadzeniu bobrów wyraźnie się poprawił. W stosunku do porównywalnych odcinków potoków bieszczadzkich zagęszczenie ryb i biomasa były tu bardzo wysokie.

Back from the Brink: The Holocene History of the Carpathian Barbel Barbus carpathicus

As a result of specific adaptations and habitat preferences strongly rheophilic fish species may show high levels of endemism. Many temperate rheophilic fish species were subjected to a series of range contractions during the Pleistocene, and then successfully expanded during the Holocene, colonising previously abandoned areas. The Carpathian barbel (Barbus carpathicus Kotlík, Tsigenopoulos, Ráb et Berrebi 2002) occurs in the montane streams in three basins of the main Central European rivers in the northern part of the Carpathian range. We used genetic variation within 3 mitochondrial and 9 microsatellite loci to determine a pattern of postglacial expansion in B. carpathicus. We found that overall genetic variation within the species is relatively low. Estimate of time to the most recent common ancestor (tMRCA) of mitochondrial sequences falls within the Holocene. The highest levels of genetic variation found in upper reaches of the Tisa river in the Danube basin suggest that glacial refugia were located in the south-eastern part of the species range. Our data suggest that the species crossed different watersheds at least six times as three genetically distinct groups (probably established in different expansion episodes) were found in northern part of the species range. Clines of genetic variation were observed in both the Danube and Vistula basins, which probably resulted from subsequent bottlenecks while colonizing successive habitats (south eastern populations) or due to the admixture of genetically diverse individuals to a previously uniform population (Vistula basin). Therefore, B. carpathicus underwent both demographic breakdowns and expansions during the Holocene, showing its distribution and demography are sensitive to environmental change. Our findings are important in the light of the current human-induced habitats alterations.

Concrete slab ford crossing – an anthropogenic factor modifying aquatic invertebrates communities

Unimproved fords provide an easy and inexpensive method of stream crossing. However, vehicles compact the stream bottom and flatten the banks. One simple and relatively permanent solution to this problem is the use of concrete slabs, which can hinder the movement of fish and invertebrates, especially in the presence of low water levels. Although the impact of fords on the stream invertebrate fauna seems clear, there is little available data on this topic, as most reports instead focus on water quality. The impact of a concrete slab ford on the invertebrate fauna of a foothill stream was examined which led to the hypothesis that the benthic invertebrates inhabiting the ford and stream sections immediately upstream and downstream of the crossing would differ significantly from those at a non-transformed natural site. Results revealed that the invertebrate fauna in the vicinity of the ford was altered over relatively long stream sections. The ford disrupted the natural balance between deposition and erosion, with the former dominating above the ford and the latter dominating below the crossing. In small streams, where there are often several similar crossings, this effect would likely be multiplied. The fords interference in the streams natural balance between deposition and erosion caused a change in the grain size of the substrate and altered the available organic matter, which directly affected the qualitative and quantitative composition of the macrozoobenthos. As the habitat becomes more homogeneous, the community of invertebrates becomes less diverse. Our results can support management decisions for erosion control.

Living with an engineer: fish metacommunities in dynamic patchy environments

Different environmental preferences and dispersal abilities allow fish to coexist in local communities. In the present study we analysed the effects of engineering species on the community structure based on the example of the European beaver (Castor fiber) and mountainous European stream fish. We hypothesised that the creation of beaver impoundments increases environmental heterogeneity and causes a strong spatial and temporal variation in fish species composition and size structure. Finally, we placed these results in the context of the metacommunity theory. Our research was conducted over a large spatial scale, and over a relatively long (5-year) temporal scale. Data analysis revealed strong environmental gradients associated with stream size and increased environmental heterogeneity associated with the creation of beaver impoundments. The results also indicated strong spatial and temporal variation in fish species composition and size structure associated with this environmental heterogeneity. Although local communities changed over time, the main metacommunity characteristics remained constant. Fish must move and follow environmental changes for their populations and communities to persist in streams inhabited by beavers. Gaining a deeper understanding of the effects of the engineering species on fish community structure may help inform management and the conservation of stream ecosystems.

Possibilities of fish passage through the block ramp: Model-based estimation of permeability

Block ramps offer an opportunity to combine hydrotechnical structures with fish passages. The primary study objective was to evaluate the effectiveness of a block ramp for upstream fish movement in a mountain stream. Geodetic measurements of the bottom surface and water level were taken for three cross-sections. The description of the geometric and hydrodynamic parameters of the block ramp was supplemented with information on the width and length of crevices between boulders. Measurements of the geometric and hydrodynamic parameters of the block ramp were performed at 76 measurement sites, at three different types of discharge. Ichthyological data were collected in the analyzed stream. Measurements covered among others total length, width, and height of caught fish. Salmonid, cottid, balitorid, and cyprinid fish were studied. The determination of the main effects of the geometric and hydrodynamic parameters of the block ramp on the possibilities of use by target fish species employed generalized linear models (GLMs). The study shows that the block ramp cannot provide longitudinal connectivity and migration of fish occurring in the mountain stream. According to estimates, the block ramp did not meet the permeability expectations. The reason for low usefulness of the ramp for fish is particularly excessively strong water current. The stream concentration constituted an unsurmountable velocity barrier for fish moving upstream for each of the analyzed discharges. The developed model suggests that some crevices in the side zones of the ramp could be parts of the migration corridor, but only for small and medium-sized fish. At medium and high water stages, movement of fish in crevices was difficult due to fast water current, and at low and very low discharges, some crevices lost their permeability, and could become ecological traps for fish. The necessity of estimation of ramp permeability during pre-construction phase was emphasized.