The perch is a very common fish in Europe. They are especially abundant in the northern parts. It can be found from north of Sweden to Spain in the south.In Denmark it is found in 96 % of all lakes. Only small, very isolated lakes have shown not to have perch. Perches are therefore the second most abundant fish species just after the roach. 

It is also very common in rivers. River systems that have a connection to a lake, make the perfect conditions for perch to thrive. This also makes the connection to brackish perch that live in less salty waters. They are most common in fjords, where concentration of saltwater levels is low.

Where is it most common

The perch can thrive in most places, but their preferred place is larger lakes with clear water, where there is vegetation close to the bank. Their most preferred habitat is in depths less than 10m and they are only very rarely found deeper than 25 m. The weeds are very important to the perch. This is where it can hide and find food. It is especially important to the fry.

In nutrition poor environments, the perch will most often be dominating. In some of these nutrition poor lakes, it has been recorded that upwards as 90 % of the total fish population has been found to be perch.

When the perch reaches 15cm, it starts to become a predatory fish, which target bigger prey, such as roaches, sticklebacks, gobies, bleaks and so on

Many small and few big ones

In a lake with good conditions, it is normal to find many small specimens and only a few big ones. A survey found that in a 22 acres lake, there were only around 300 perch past the 25 cm mark. Populations with this few amounts of specimen fish can easily be overfished.

The amount of male and female specimens tends to be 1:1 up until they get mature. After spawning, there will typically be an overrepresentation of females, since the male grow slightly slower, which makes them vulnerable to predators.

The perch does not need high quality spawning areas, but one thing that determines how many will come from spawning is the degree of cannibalism. In some cases, cannibalism can affect that only 0,001‰ will survive and in  other cases 11‰ will survive if cannibalism is low. So, it can vary very much, how many will survive.

What does the perch eat?

The only limitation the perch has, is that it cannot chew its prey, so it must swallow its prey in one. In the early stage, the perch start out by eating plankton. After only a few weeks, it starts to focus on more energy rich food items, such as daphnia. After it reaches 3 cm, it starts to eat worms and larvae. When the perch gets bigger than 15cm, it can become an effective predator and eat fish, such as sticklebacks, small roaches, bleaks, gobies and so on. Most often, it will target the prey that requires the lowest amount of energy to catch, with the biggest reward.

Temperature and salinity

They love warm water and thrive up until 28 degrees Celsius. The perfect growth temperature is 23 degrees Celsius, but they can survive temperatures of 31-32 degrees Celsius.

In brackish waters, the perch will thrive at a salinity level of 10‰ but is almost certain to die, if the salinity level reaches 15‰. Though, local adaption and genetics, can affect that the perch can survive in higher levels.

Perch in the middle

If a lake has a population of pike, perch and zander, the pike will be most dominant in the shallow areas and the zander will dominate the deeper parts. This makes the perch be in a bit of a clinch between the two species, because the perch likes to be in the middle, where the water gets deeper. In deeper lakes it is not a problem, but if the water level is lower, this will decrease the optimal living conditions of the perch. This is actually not good, if seen from an environmental viewpoint. If the zander becomes more dominating, the perch numbers will decrease, and less plankton will be eaten.

Age

A perch will normally be 6-9cm after a year and around 10-15cm after 2 years. The males mature later than the females. Typically, the perch will be mature from 6-16cm whereas, the female will have to wait until they are between 9-25cm.

Spawning

The perch spawn in the springtime, but the exact time can vary from early February to July even. The hatch will happen after 7-18 days and is depending on the temperature. A perch can carry from 1000 to 200.000 eggs, depending on her size. In a lake with large populations, there can be laid up to 2 million eggs pr. acre. The eggs are attached to a string and the females swim in circles until it has been laid. Most often, she will be followed by 1-5 males, all fighting to fertilize the eggs. This happens in shallow water with lots of vegetation.

The perch is a predator that knows how to adapt to many conditions and is one of the most common species in Europe