onte ▁T res a . ▁ ▁In ▁ 1 8 9 5 ▁the ▁bro ok ▁tr out ▁was ▁introduced ▁from ▁Lake ▁Zug , ▁while ▁between ▁ 1 8 9 4 ▁and ▁ 1 8 9 7 ▁the ▁common ▁white fish ▁was ▁introduced . ▁Since ▁ 1 9 5 0 ▁attempts ▁have ▁been ▁made ▁to ▁introduce ▁the ▁white fish ▁Cor eg on us ▁macro ph th al mus ▁from ▁Lake ▁Ne uch ât el , ▁but ▁it ▁has ▁not ▁established ▁itself ▁effectively . ▁ ▁The ▁Common ▁Ro ach ▁is ▁present ▁in ▁large ▁numbers ▁and ▁took ▁around ▁ten ▁years ▁to ▁colon ise ▁the ▁entire ▁lake , ▁thereby ▁replacing ▁the ▁ble ak . ▁Still ▁present ▁are ▁the ▁European ▁ch ub , ▁ten ch , ▁car p ▁and ▁a ▁few ▁examples ▁of ▁European ▁per ch , ▁larg em outh ▁bass , ▁z ander ▁and ▁bur bot . ▁Rec ently ▁the ▁w els ▁cat fish ▁has ▁also ▁been ▁sp otted , ▁and ▁the ▁p igo ▁has ▁also ▁been ▁sp otted ▁too . ▁ ▁F oss ils ▁The ▁whole ▁area ▁behind ▁the ▁southern ▁sh ores ▁of ▁Lake ▁L ug ano ▁is ▁rich ▁in ▁foss ils . ▁The ▁foc al ▁point ▁of ▁these ▁foss il ▁depos its ▁is ▁Monte ▁San ▁Giorg io , ▁where ▁since ▁the ▁ 1 9 th ▁century ▁many ▁foss ils ▁have ▁been ▁found ▁d ating ▁from ▁the ▁mid - Tri ass ic ▁( around ▁ 2 2 0 ▁million ▁years ▁ago ). ▁The ▁depos its ▁on ▁Monte ▁San ▁Giorg io ▁stretch ▁towards ▁the ▁west ▁into ▁Italian