European Perch (Perca fulviatilis)

European perch, also known as redfin perch, is a native non-migratory freshwater fish species and is common in all UK freshwater habitats predominately due to stocking of waterways for the angling community; perch are thought to be rarer in Scotland. The species was introduced to Ireland around the 18th century and is considered invasive in some parts of the world.

Perch are characteristic in appearance, with bold black tiger-like striping and orangey-red pelvic and anal fins. Fin colouration is dependent on the turbidity of the water, good light penetration results in bolder colouration and poor light penetration with little vegetation results in lighter coloured fins. Crustacean diet can alter colouration to reddish yellow. Perch are visual predators, as indicated by their large eyes, and feed on other fishes, invertebrates, and crayfish.

They are often found in shoals and spawn between February and July amongst vegetation and rocks. Depending on water temperature, eggs typically hatch within 16 days and emerge as small fry. On emergence, fry will feed on the yolk sac for their first week. Water temperature also plays a large role in juvenile survival; colder summer temperatures increase juvenile mortality rate whereas warmer summers may result in larger, stronger shoals of young perch.

Traditional survey methods include using artificial spawning substrates and collecting egg strands from April to June. eDNA analysis can aid this method to monitor spawning in freshwater systems and inform fishery management.

• Avoid stepping into the water – this can stir up sediment, throwing up sediment DNA and any inhibitory molecules present. Sediment may clog the filter and prevent sufficient volumes of water being filtered.