This week’s #FishInThePost question was, ‘which freshwater fish have been known as the wolves of the river?’ The answer we were looking for was the European Perch (Perca fluviatilis) and it was correctly guessed by @UnderwaterMedia. We were also very taken by the lovely photo of a Perch shared by @UnderwaterMedia and look forward to more fishy photos from them on Twitter. 


Photo of European Perch shared by #FishInThePost winner @UnderwaterMedia

In fact, @UnderwaterMedia also guessed (along with @AgentRedSquirrl) that this week’s #FishInThePost was Northern Pike, which we later found out is a freshwater fish species known as the ‘Water Wolf’. This name is linked to Pike because although the species is predominantly regarded as solitary predators, similar sized pike can be known to cooperate during hunting. However, we were looking for Perch. European Perch have been coined by many as the ‘wolves of the river’ due to their ‘pack’ like approach to hunting prey which includes macroinvertebrates and fish, often targeting their bodies with their attacks.


European Perch (Perca fluviatilis) drawn by Steph Januchowski-Hartley.

Perch are widely recognised by their distinctive spiky dorsal fine. They are rough to the touch because they produce low amounts of mucus. The colour of the perch actually depends on the habitat in which they live. In shallow areas where light penetration is good, they are often darkly coloured, but in poorly lit areas without vegetation they are lightly coloured (CABI, 2018). However, Perch are typically a yellow-olive green colour with black bands running vertically. 

Perch have also been used in multiple management projects within eutrophic lake systems, whereby their fierce predation on cyprinid species allows zooplankton communities to proliferate and subsequently reduce the spread of algal blooms (Yazıcıoğlu et al., 2016). Moreover, their predatory feeding behaviour may have wider management applications for the control of invasive species, such as non-indigenous crayfish species which are susceptible to predation from Perch (Gherardi et al., 2011).


CABI (2018) Invasive Species Compendium: Perca fluviatilis (Perch). Available online through <;. [Accessed 15/02/2019].

Gherardi, F., Aquiloni, L., Diéguez-Uribeondo, J. and Tricarico, E. (2011). Managing invasive crayfish: is there a hope?. Aquatic Sciences73(2). 185-200.

Yazıcıoğlu, O., Yılmaz, S., Yazıcı, R., Erbaşaran, M. and Polat, N. (2016). Feeding ecology and prey selection of European perch, Perca fluviatilis inhabiting a eutrophic lake in northern Turkey. Journal of Freshwater Ecology31(4), pp.641-651

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