The impact of water level fluctuations on the year class strength of roach: Implications for fish stock management

Abstract

Water level fluctuations in a drinking water reservoir (Saidenbach Reservoir, Saxony, Germany) and length-frequency data of roach (Rutilus rutilus) derived from gillnet catches were studied over a period of eight succeeding years and subsequently analysed with respect to level change and cohort establishment. The results indicate a strong impact of water level on the year class strength of roach. Constantly high water level with large areas of inundated plants led to a very strong roach year class. Conversely, decreasing water level shortly after the spawning period was found to result in a total loss of the new roach year class. Any other possible factors influencing year class strength of roach (such as food, temperature, winter duration) may only play a role if the water level after spawning remained relatively stable. Consequently, water quantity management in reservoirs can be used as a biomanipulation tool to reduce the planktivorous fish stock and to improve water quality, which should be an interesting option especially in drinking water reservoirs.

Ecological impacts of winter water level drawdowns on lake littoral zones: a review

“…Impacts are most extreme when regulated water levels are unnaturally low before and during spawning Noble 2002, 2005;Kahl et al 2008), and during YOY hatching, such that there is limited habitat availability and suitability (Gafny et al 1992;Wilcox and Meeker 1992), strongly impacting recruitment and year-class strength (Kohler et al 1993;Neal et al 2001;Ozen and Noble 2005). Regulated water level fluctuations (e.g., rises and recessions) during spawning can negatively affect juvenile fish densities (Miranda and Lowery 2007), partly due to the loss of physical structural complexity (Neal et al 2001).…”

“…Seasonal and inter-annual water level fluctuations influence the survival of numerous flora and fauna in the littoral zone (Hill et al 1998;Riis and Hawes 2002;White et al 2008). High flows and flooding release nutrients from riparian areas (Baldwin and Mitchell 2000) and provide spawning habitat for numerous fish species (Kahl et al 2008;Gertzen et al 2012). Sediment dewatering and subsequent desiccation stimulates macrophyte species propagation and enhances nutrient cycling (Keddy and Reznicek 1986;Hill et al 1998;Baldwin and Mitchell 2000).…”

Environmental drivers of fish spatial distribution and activity in a reservoir with water level fluctuations

“…WLF may alter spawning habitats availability and, as a consequence, reproduction success (Gafny et al, 1992;Clark et al, 2008;Kahl et al, 2008), with different sensitivity degrees according to species requirements in terms of spawning substrates. Analysis of time series allows to relate water level and amplitude of WLF with spawning success or failure and thus with population dynamic (Ostrovsky & Walline, 2000;Kahl et al, 2008;Webb, 2008;Ostrovsky et al, 2013). In addition, WLF alter number of fish refuges (Gasith et al, 2000;Fischer & Ohl, 2005).…”

Habitat use and preference of adult perch (Perca fluviatilis L.) in a deep reservoir: variations with seasons, water levels and individuals

“…Indeed, WLF can lead to loss of potential prey (Winfield, 2004), loss of refuge areas (Kaczka & Miranda, 2014) and loss of spawning habitats (Hudon et al, 2005) for fish fauna. Finally, WLF may also decrease fish recruitment if WL drops after spawning (Kahl et al, 2008) and fish eggs desiccate (Michaletz, 1997;Winfield, 2004). Therefore, Coops et al (2003) and more recently Tao et al (2016) highlighted the urgency of collecting ecological data on fish-habitat relationship.…”