Piscivorous Perch Perca Fluviatilis Research Articles

Rapid proliferation of an endemic galaxiid following eradication of an alien piscivore (Perca fluviatilis) from a reservoir.

Following the complete eradication of the alien piscivorous perch Perca fluviatilis from a potable reservoir, the abundance of the endemic western minnow Galaxias occidentalis, which was previously undetectable prior to the initial eradication event, increased dramatically. The study reveals the potential of reservoirs to act as ecological refuges and has implications for understanding the relative effects of alien fishes v. habitat alteration on native freshwater fishes.

Total mercury in sediments, macrophytes, and fish from a shallow steppe lake in eastern Austria.

During summer 2011, samples of sediment, macrophytes, and fish tissues from the shallow, slightly alkaline Lake Neusiedl, Austria, were evaluated for their total Hg content. This is the first report of Hg levels from this lake. Sediments displayed Hg contents between 0.025 and 0.113 μg g(-1) dw (dry weight), significantly correlating with the proportion of organic components pointing to a small anthropogenic impact on the lake's Hg content. Hg Levels in plants and fish were unexpectedly high: both investigated submerged plant species, Potamogeton pectinatus and Myriophyllum spicatum, showed mean values of 0.245 ± 0.152 and 0.298 ± 0.115 μg g(-1) dw, respectively. Biomagnification was evident when comparing muscle samples of the planktivorous fish species rudd Scardinus erythrophthalmus (n = 10, mean = 0.084 μg g(-1) ww (wet weight)) with the piscivorous perch Perca fluviatilis (n = 21, mean = 0.184 μg g(-1) ww) or pike-perch Sander lucioperca (n = 9, mean = 0.205 μg g(-1) ww). Significantly lower values were found in the muscle of the piscivorous pike Esox lucius (n = 25, mean = 0.135 μg g(-1) ww), pointing to a specific Hg metabolism of this fish, presumably under the particular physicochemical properties of the lake. Hg Concentrations in fish could pose a risk to piscivorous birds in this protected wetland system.

Total Mercury in Lake Neusiedl, Austria

Between May and September 2011 a total of 361 samples from water, sediment, macrophytes and fish tissues from the shallow, slightly alkaline Lake Neusiedl were measured for their total mercury content with cold vapour atomic absorption spectroscopy (CV-AAS). Hg content of surface water was below the LOD of 0.1 μg/L and the sediments displayed contents between 0.025 and 0.113 μg/g dw, significantly correlated with the proportion of organic components (fig 1). Although these results do not point to an anthropogenic pollution of the lake, considerable amounts of mercury could be measured in fish samples and macrophytes. Both investigated submerged plant species, namely Potamogeton pectinatus and Myriophyllum spicatum show a high potential for bioaccumulation of Hg, presenting mean values of 0.245 ± 0.152 and 0.298 ± 0.115 μg/g dw respectively. Compared to freshwater fish from other unpolluted sites high amounts of Hg could be measured (fig. 2). Biomagnification and significant differences could be observed when comparing muscle samples of the planctivorous fish species rudd Scardinus erythrophthalmus (n = 10, mean = 0.084 μg/g ww) with the piscivorous perch Perca fluviatilis (n = 21, mean = 0.184 μg/g ww) or pike-perch Sander lucioperca (n=9, mean = 0.205 μg/g ww) respectively. Significantly lower values were measured in the muscle of the piscivorous pike Esox lucius (n = 25, mean = 0.135 μg/g ww) in which a strong correlation between fish age and Hg content did not occur. In addition the muscle/liver ratio of Hg in pike was significantly lower compared to the other fish species, which points to a different Hg metabolism in pike, maybe under the specific saline alkaline conditions of this lake.

Size‐dependent predator–prey relationships between perch and their fish prey

Size‐dependent interactions between piscivorous perch Perca fluviatilis (age ≥1 year) and their fish prey age 0 year perch, pikeperch Sander lucioperca and roach Rutilus rutilus in the biomanipulated Bautzen Reservoir indicated that the highest ratio of prey total length (LT) to predator LT was 59%. Perch LT and prey fish LT were positively and linearly related. Perch LT was strongly related with both gape width and gape height. Within the range 80–110 mm LT, the gape height of perch exceeded gape width, while beginning at 120 mm LT the gape width exceeded gape height. The minimum, maximum and mean prey LT and prey body depths of all three prey species increased with increasing predator size, but the increases in mean sizes of perch and pikeperch as prey were less than that of roach. The low limit of the ‘predation window’ observed in this study coupled with results of previous studies on perch in the Bautzen Reservoir indicated that perch had a major impact on the population dynamics of both perch and pikeperch.