Exacting fish
Bound of vendace's natural spread in Finland goes with neck of land of Maaselkä. Also lake Inari has vendace population which has spread to it from Alajärvi where vendaces were put in 1964-66.
Vendace don't tolerate salt water. Therefore in the Baltic there are reproductive vendace-populations only in bays. Inlands typical vendace-lake is big or medium, quite deep lake. Colour of water is not a critical issue, but it is supposed that vendace favours clear water. Only turbidity by clay is not suitable. Also shallow eutrophic lakes are uncomfortable or not suitable at all, because vendace needs much oxygen (at least 4 ml/l) and also layered water with cold bottom also through summer.
Food taking and moves
Vendaces eat zooplankton: little water fleas and other crustaceans. Plankton move up and down depending on light through day. Vendaces follow plankton. In summer plankton is in deep daytimes and lifts up to the surface at night. Colour of water take effect to those vertical moves and cause differences between lakes. In summer people talk "vendace goes to the grave", so to the depths they go. Reason to this is supposed to be in cold water and probably moves of plankton as well.
Like other fish that feed on plankton, vendaces are almost all time on the move and eat a lot. There's still a feeding peak from summer to autumn.
Spawning
The most of vendaces spawn in autumn. Water temperature triggers spawning. It starts when temperature of water have dropped to +5-7 C. Most frequently the spawning begins at the turn of October and November, but could take place in some lakes in turn of the year. There are also populations that spawn in winter, in February and March.
Spawning areas are on slopes of deep places, usually in 1-5 m, but depth varies among populations and lakes and even with weather. Bottom must be hard: sand, clay or thin grit.
Vendace spawn in shoals.
Catches, records and ways to fish
Vendace is the most important fish to pro fishermen of inland waters in Finland (Catch in 2006 nearly 2500 tonnes). In some regions fishing vendace offers notable extra incomes. E.g. my grand father always keeps saying that shores of Konnevesi (famous vendace-parish) are built with vendace. Also recreational fishers are after vendace (1500 tn in 2006).
Traditional way to catch vendace in Finland is seine fishing. Fishing with nets can be successful too. Some fishermen also trawl vendace. Vendace-rush in lake Inari is still in remembrance: it was sudden reality that lake was full of valuable fish and (too) many trawlers emptied it fast. Today population is recovered.
At the time of writing this, official vendace record is 0,55 kg from lake Inari. In old books were 0,8 kg entry from Sorsajärvi of Posio.
Sources:- Koli, Lauri, Suomen kalat
- FGFRI's stats (In Finnish)
- Fish records (In Finnish)