Author: Momigliano, Denys, Jokinen & Merilä, 2018
FBname: Baltic flounder
Remark: This species would be the result of the first colonization of the Baltic Sea at its opening, the ancestral population having colonized a seconfd time while <i>Platichthys solemdali</i> was already differentiated (Momigliano et al. 2018: Ref. 119386).  Further genetic evidence is need to confirm this species, but life-traits evidence suggests that this population should be considered as separated stocks.
Comments: This demersal species has been reported to have adults reside in the archipelago and coastal areas throughout their lives undertaking only limited migrations between deeper wintering grounds and shallower spawning and feeding areas. It lives in brackish water of varying salinities at 0.5 to 50 m depth on soft and hard bottoms. It is a benthivore, feeding on various mussels and other benthic invertebrates from its postsettled juvenile stage. Spawning occurs in April to June in nearshore areas 5-20 m depth, preferred  water temperature of around 8°C. Mature females are reported lay up to 2 million relatively small eggs after fertilization develop on the bottom, above stony, sandy, or vegetated substrates. Little is known about its larval phase, while early development and juvenile habitat use generally resembles the common features of flatfishes. There are no studies specifically done on age and length at maturity for demersal Baltic flounder. However, around Gotland in the central Baltic Sea (SD 28) where both <i>P. flesus</i> and <i>P. solemdali</i> species co-occur, female flounders recruit to the adult population and attain maturity around the age of 3 years (range: 2-5) at a length of 20-25 cm, while males often maturing earlier (2-3 years) than females (3-4 years) (Ref. 119386).