Effects of hydropeaking on the attached eggs of a rheophilic cyprinid species

Abstract

Human‐induced changes in the hydrological regimes of lotic waters such as hydropeaking have significant negative impacts on riverine life. However, the impacts of dynamic changes in water flow on adhesive fish eggs are not very well known. We focused on the effects of hydropeaking on the spawning ground of a rheophilic cyprinid fish, the asp (Leuciscus aspius). We tested whether a sudden increase in water velocity caused by hydropeaking may have negative effect on the adhesive eggs by the combination of field observations and laboratory experiments. The main objectives of the study were to (i) investigate abiotic characteristics of an asp spawning ground, (ii) monitor egg densities in relation to hydropeaking events and (iii) test detachment rates of the asp eggs in laboratory conditions in relation to water velocity. The asp spawning ground was associated with shallow water depths (0.2–0.4 m) and flowing water (0.1–0.4 m s−1) during base flow. The water velocity that occurred on the spawning ground during the hydropeaking event was measured to be from 0.7–1.2 m s−1. Asp eggs nearly disappeared from the spawning ground before their hatching time probably due to several hydropeaking events. The laboratory experiments showed the significant dependency of egg detachment rates on the water velocity and substrate type with a critical value of 0.7 m s−1. Our data suggested that eggs may be negatively impacted by flow alterations. Avoiding hydropeaking or keeping water velocity below critical values is recommended for the management of rheophilous fish spawning grounds.

SEM images reveal intraspecific differences in egg surface properties of common nase ( Chondrostoma nasus L.)

“…This is of particular importance as severe recruitment problems may arise from a combination of stressors such as a poor egg quality, a reduced adhesive ability resulting in higher off‐drift of eggs and deteriorated habitat conditions on spawning grounds. Additionally, recent findings demonstrate that egg adhesiveness at spawning grounds can be extremely reduced in rivers with hydropeaking effects (Bartoň et al., 2021). In turn, improvement of spawning ground quality might partially compensate for reduced egg quality as a loose and porous interstitial as well as low fine sediment infiltration rates positively contribute to hatching success (Nagel et al., 2020a; Nagel et al., 2020a).…”

“…Patzner et al., 2006; Petz‐Glechner et al., 1998; Riehl et al., 2002). This ensures that a large proportion of the eggs laid adhere to surfaces at spawning sites, which in these species are often characterized by medium to rapid current velocities (Bartoň et al., 2021; Melcher & Schmutz, 2010). This is particularly evident in common nase ( Chondrostoma nasus L.) which spawns its eggs at current velocities of up to 1 m/s or even greater (Melcher & Schmutz, 2010; Nagel et al., 2020b).…”

Does Fish Conditioning in Aquaculture Increase Survival Success in the Wild? A Case Study on a Cyprinid Fish

“…The 6149 individuals were released in the Želivka Reservoir on 19 May 2020, and the remaining 1426 asp from semi-natural experiment trained on northern pike direct predation were released on 29 July 2020 (7575 individuals in total). The study site has the largest population of asp in the country and is protected by Natura 2000 [7]. The shoreline of Želivka Reservoir was sampled with an electrofishing boat (electrofisher EL 65 II GL DC, Hans Grassel, Schönau am Königsee, Germany, 13 kW, used voltage and current 500 V, 10 A, pulsed DC, frequency 70 × s −1 ) in 24-26 August 2020, on 18 March to 25 April 2021 during the spring spawning migration of asp [48] and on 25-27 August 2021 (Figure 2).…”

“…Populations of many fish species are declining worldwide [1][2][3]. The reasons for declining fish populations are diverse, ranging from habitat alteration to invasions of non-native species [4][5][6][7]. In the freshwater environment, migratory rheophilic fish species are a particularly threatened group [8][9][10].…”

Understanding Nutrition and Metabolism of Threatened, Data-Poor Rheophilic Fishes in Context of Riverine Stocking Success- Barbel as a Model for Major European Drainages?

“…Declines have been most substantial for the gravel-spawning species of the hyporhitral and epipotamal streams in medium- and large-sized rivers (e.g., grayling Thymallus thymallus, nase Chondrostoma nasus , barbel Barbus barbus ) further aggravated by their much longer generation time over smaller fishes [ 1 ]. The reasons for this decline are many, and to name a few, they are river (habitat) fragmentation [ 4 ], the effects of increasing temperature, and increasing fine sediments [ 5 ] or altered river flow and hydropeaking [ 6 ]. In central European rivers, Mueller et al [ 1 ] identified fish species that deserve higher priority in conservation management, and half of them are large potamodromous rheophilic cyprinids.…”