Patterns in diel habitat use of fish covering the littoral and pelagic zones in a reservoir

Abstract

We investigated diel habitat use of fish covering the littoral and pelagic zones of the Ř ímov Reservoir (Czech Republic) and analyzed the influence of predator presence and of shifting feeding habitats in all dominant species and age groups. Our sampling revealed distinctive diel changes of fish distribution in the reservoir, which were age-and species-dependent. The overall abundance of subadult fish in littoral habitats was significantly higher at night than during the daytime. Subadults were almost absent in pelagic habitat during the day and their presence increased during the night, although densities were smaller than in the littoral. Adults preferred the pelagic zone during the day and partly migrated to the littoral at night. Potential fish predators were most likely responsible for small fish avoidance of the littoral and pelagic zones during day. Higher availability of food in the littoral was the most important driver of the high occurrence of subadults at night. Day preference of pelagic zone by adults is most likely caused by higher profitability of this habitat in comparison with littoral. The reasons for night inshore migration of adults are not obvious, but the homogenization of their distribution or resting in the littoral could explain such behavior.

Effects of differing ground‐truth data, transect design and statistical analysis on the repeatability of hydroacoustic assessments of pollan Coregonus autumnalis pollan

“…Therefore, it is possible that alternative fish distribution or behaviour over the diurnal cycle drove these differences (Mehner, ). Alternatively, the higher percentage of small targets could be the product of horizontal migrations from the littoral zones, as small fish move out to feed on zooplankton in darkness when predation risk is lower (Říha et al., ). However, this explanation is less likely as there was no significant increase in abundance.…”

Complementarity of two high-resolution spatiotemporal methods (hydroacoustics and acoustic telemetry) for assessing fish distribution in a reservoir

“…Hydroacoustics and netting Baldwin & Polacek, 2011; Mu ska et al, 2013 Hydroacoustics, gillnetting and others (scuba diving or ichthyoplankton net) Imbrock et al, 1996;Prchalová et al, 2003, Hydroacoustics and net towing Kratochvil et al, 2010Hydroacoustics and radio telemetry Grimardias et al, 2017Hydroacoustics and acoustic telemetry Lyons & Lucas, 2002McGrath et al, 2003;Dunlop et al, 2010Acoustic telemetry and gillnetting Smith et al, 2011Radio telemetry and mark-recapture Auer, 1999Radio or acoustic telemetry, PIT tags Caswell et al, 2004Binder & McDonald, 2007Mark-recapture and PIT tags Caroffino et al, 2009Gillnetting and electrofishing Mehner et al, 2005 Beach seining, electrofishing and purse seining Ríha et al, 2015 and low depth within the reservoir that may drive fish distribution: the upstream (sandy beach/mud with stumps) and the bay area (sandy beach/mud) (Roy, 2014) (Fig. 1).…”

“…For instance, juveniles and adults generally migrate in opposite horizontal directions: juvenile fish perform night offshore migration (Romare et al, 2003;Gliwicz et al, 2006), whereas adults perform night inshore migration (Kube cka, 1993;Kube cka & Duncan, 1998;Zamora & Moreno-Amich, 2002;Jacobsen et al, 2004;Ríha et al, 2011). Migration does not concern the entire population, and plasticity in the pattern of fish migration can occur (Eriksson, 1978;Busch & Mehner, 2012;Mehner & Kasprzak, 2011;Ríha et al, 2015). The spatial distribution of the fish community is also structured along longitudinal and vertical gradients.…”

Do diel variations in stream fish assemblages depend on spatial positioning of the sampling sites and seasons?

“…In freshwater systems for example, diel changes have been found to be significant in the littoral zone of lakes and reservoirs (Baumann & Kitchell 1974, Lewin et al 2004, Riha et al 2015 and rivers (Sanders 1992, Copp & Jurajda 1993, Arrington & Winemiller 2003, ErŐs et al 2008. Several studies showed that night time samplings yielded more species and specimens and greater biomass than day time samplings in the nearshore habitats of rivers because of higher catching efficiency, diel migration of many species to the littoral zone and higher movement activity by night (Copp & Jurajda 1993, Wolter & Freyhof 2004, ErŐs et al 2008.…”

“…Daytime samplings showed that tributary mouths are more intensively used by mainstream fishes as refugee and feeding areas than more upstream reaches (Osborne & Wiley 1992, Schlosser & Angermeier 1995, Thornbrugh & Gido 2010. Therefore, assemblages close to the mouth may be more variable than more upstream sites (ErŐs & Schmera 2010, Roberts & Hitt 2010). Since fish migration patterns can be more intense downstream and may show a diel pattern, it can be hypothesized that differences between day and night samples will be the most contrasting close to the tributary mouth and may mitigate upstream as the number of migrants from the species pool outside the focal stream diminish.…”