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Such a female is only starting her spawning

 

 

For the female trouts the spawning is a difficult and heavily energy-demanding process. They select the spawning ground, dig the spawning nest, the roe is laid by portions (they spawn repeatedly), they cover the roe that was spawned by them and then fertilized by a male with gravel again (the roe will incubate for up to five months). During the incubation the roe cannot be left buried under bottom sediments, in that case it simply perishes; instead it must be exposed to the oxygen in flowing water. The bellies of females that have already spawned some of their roe portions look much smaller (note the fold on the belly).

 

The larger individuals that have appeared in camera view may have weighed around a kilo and a half; they spawn more than one and a half thousand roe grains! They will spawn the roe by portions of a couple of hundred grains. The diameter of a roe grain is about 4-5 millimetres.

 

The fish that spawn for the first time are 3-4 years old, length 25-32 centimetres and they  manage to produce only a couple of hundred roe grains.

 

Young milt fish become sexually mature one year earlier, when they are only about twenty centimetres, but it is another question if the proper, experienced male spawners allow such youths to take part. In camera view we have seen the ”established ladies” politely sending off the youngsters that circle around them…

 

A little more about the looting of the spawning ground by the mallards: they have surely not destroyed all the spawned roe from the about twenty trout pairs that have been active in camera view. Despite this the looting has been significant. But part of the fertilized roe has certainly been left hidden in the gravel.

 

Let us be observant, and see how it turns out eventually. The mallards have repeated the plundering during  recent nights, and yesterday they were already five instead of three…