Stav populace bolena dravého (Leuciscus aspius) v EVL Želivka a sekavce podunajského (Cobitis elongatoides) v EVL Nová Říše: Current status of asp (Leuciscus aspius) in Želivka Reservoir Special Area of Conservation and Danubian spined loach (Cobitis elongatoides) in Nová Říše Reservoir Special Area of Conservation

V roce 2015 proběhl detailni monitoring populaci bolena draveho v EVL (evropsky významna lokalita) Želivka a sekavce podunajskeho v EVL Nova Řise. Cilem studie bylo stanovit zakladni populacni parametry populaci těchto druhů, rekonstruovat jejich dlouhodobý vývoj a posoudit jejich aktualni stav v zavislosti na ohrožujicich vlivech v lokalitach. Třeci hejno bolena draveho bylo sledovano v přitokove casti nadrže Želivka (Svihov) při migraci na trdlistě na přelomu března a dubna. Celkova pocetnost třeciho hejna bolena draveho byla pro rok 2014 odhadnuta na 2086 jedinců s mirnou převahou samic. Odhad odpovida dlouhodobemu průměru pocetnosti od roku 1985. Jako potencialně negativni vlivy se zdaji být extremně prostorově omezena trdlistě ci manipulace s průtoky v průběhu třeni. V cervnu a v zaři byla sledovana relativni pocetnost sekavce podunajskeho na 7 lokalitach v nadrži Nova Řise a to ve dne i v noci. Pocetnost dosahovala průměrně 40 ind. na 100 m břehu s převahou samců. Vyssi pocetnosti sekavců byly větsinou zaznamenany ve dne než v noci a v cervnu než v zaři. Zařijový pokles pocetnosti byl spojen s poklesem zastoupeni samic. Z dlouhodobeho pohledu představuji aktualni výsledky pokracujici pokles pocetnosti patrný od roku 2008. Jako možný negativni vliv bylo identifikovano kolisani vodni hladiny spojene s ustupem submerznich makrofyt. Abstract:  Detailed surveys of asp in Želivka Reservoir Special Area of Conservation (SAC) and Danubian spined loach in Nova Řise Reservoir SAC were carried out in 2015. The aim of the study was to assess the population characteristics of the target species, evaluate their long-term trends at the SACs and assess their state in the context of present threats. The spawning stock was monitored in Želivka Reservoir tributary during early spring. The overall abundance of asp spawning stock was back-calculated as 2086 individuals with a slight prevalence for females in 2014. The estimated abundance corresponds with the long-term average estimates since 1985. An extremely limited area for spawning grounds and changes in artificial water discharges during the spawning period have been assessed as potential threats. However, considering the population’s long-term stability, neither threat has had a significantly negative impact yet. The relative abundance of Danubian spined loach was recorded at 7 localities in Nova Řise, both during day and night in June and September. The abundance reached 40 ind. per 100 m of shoreline on average, with a higher prevalence of males. Daytime abundances of Danubian spined loach were higher than nighttime and higher abundances were recorded in June than in September. The reduced abundance in September has been associated with an increased male-bias in the population. In terms of the long-term population dynamics, the observed abundance continues to decline slightly as has been apparent from 2008. Water level fluctuations and the decline of submerged macrophytes have been identified as the main threats.