Economically important, pretentious to quality of water
Whitefish exist in whole Finland. It has also been put into waters a lot during 100 years already. Although occurrence covers the whole land, there's whitefish not nearly in every lake. Whitefish exists also practically through whole coastal sea area of Finland.
Whitefish demand cold water also in summers. So lake can't warm up thoroughly, it must be layered with cold bottom water. Need of oxygen is also high. Acidity affects at first hand to reproduction, but instilled summer-old young get on waters, where reproduction fails.
Food taking and moves
Like said before, whitefish forms that have differences in density of gills vary in food taking. All young whitefish eat zooplankton. Those with thicker "gill-stainers" eat plankton also grown-up and also Mysis-crustaceans and little fish. Those with not dense "gill-stainer" eat mainly bottom fauna but also little fish are proper food. All whitefish eat also spawn, even their own.
In sea whitefish's food-taking-wanderings can be very long. Those whitefishes that ascend the river to spawn, return to sea and wander to the borders of open sea and outer archipelago to feed. "Reef-whitefish" that live in sea move against coastline between shallow and deep water: in winter and summer they are in deep and in autumn in shallower water.
In lakes moves are the same proportion to size of water. In summer whitefishes are found certainly from deep waters.
Spawning
Whitefish spawn in autumn, September-October. Peak is in October. Some populations of small lakes of Lapland spawn in winter. In seas whitefish start wandering to spawning areas in the beginning of summer. Also inlands there is populations that ascend the rivers to spawn. Part of the whitefishes spawn in the lakes to the straits that have stream on it. At all events the spawning takes place at the areas where water is shallow and bottom is of gravel.
Catch, records and special ways to fish
Whitefish is one of the most valuable species in Finland. Especially in Lapland it has a much importance to both pro- and recreational fishers. Most usual way to fish whitefish is with nets. At sea and big lakes large fish-traps are used.
In 2006 pro fishermen caught 850 tonnes whitefish, about which 700 tn from the sea. Catch of recreational and household use fishers were quite remarkable: approx. 2500 tn.
At the time of writing this, official Finnish record of whitefish is only 7 kg. It will be higher for sure, because in old books top entry was 12 kg.
In old times people used to torch-fish whitefish when it ascended the rivers to spawn - and get huge catches. Today it is naturally forbidden. In Finnish guardianship society, man can't even buy beer whenever wants to. Couple of years a go some home-made-einstein invented to make very small wobblers. Then people noticed that when these micro-wobblers were trolled at slow speed got whitefish.
Sources:- Koli, Lauri, Suomen kalat
- FGFRI's stats (In Finnish)
- Fish records (In Finnish)