Physical and chemical water properties in water bodies inhabited by the endangered lake minnow, Eupallasella percnurus (Pall.), in central Poland

The objective of the study was to characterize the physical and chemical water parameters of Eupallasella percnurus (Pall.) habitats, to identify the habitat preferences of this species, and, in particular, to determine which parameters would be useful in selecting water bodies for translocation to establish viable new populations as part of active protection programs for this species. Results obtained from seven water bodies in central Poland over a minimum of a four-year period are analyzed. Water temperature, oxygen saturation, conductivity, pH, and concentrations of mineral forms of nitrogen and phosphorus were determined. The key parameter for assessing habitat quality was identified as water pH ranging from 4.9 to 9.1. Low pH values appear to cause disturbances in natural fish recruitment. Populations from water bodies with water pH not lower than 5.0 did not exhibit any effects of unfavorable environmental conditions despite periodic water temperatures that significantly exceeded optimal values for this species (> 25°C) and dangerously low levels of water oxygen saturation (< 14%).