▁lake ▁ret ention ▁time ▁is ▁an ▁average ▁of ▁ 8 . 2 ▁years ; ▁that ▁of ▁the ▁northern ▁bas in ▁( 1 1 . 9 ▁years ) ▁is ▁consider ably ▁higher ▁than ▁the ▁southern ▁one ▁( 2 . 3 ▁years ). ▁ ▁Places ▁on ▁the ▁lake ▁in ▁Switzerland ▁( CH ) ▁and ▁in ▁Italy ▁( I ) ▁include ▁( from ▁L ug ano , ▁clock wise ): ▁ ▁Navigation ▁ ▁The ▁lake ▁is ▁navig able , ▁and ▁used ▁by ▁a ▁considerable ▁number ▁of ▁private ▁vessels . ▁Pass enger ▁boats ▁of ▁the ▁Soci età ▁N avig azione ▁del ▁L ago ▁di ▁L ug ano ▁( SN L ) ▁provide ▁services ▁on ▁the ▁lake , ▁princip ally ▁for ▁tour ist ▁purposes , ▁but ▁also ▁connecting ▁L ug ano ▁with ▁other ▁la kes ide ▁communities , ▁some ▁of ▁which ▁have ▁no ▁road ▁access . ▁ ▁Fish ery ▁in ▁the ▁lake ▁( and ▁Lake ▁Mag giore ) ▁is ▁reg ulated ▁by ▁a ▁ 1 9 8 6 ▁agreement ▁between ▁Switzerland ▁and ▁Italy . ▁The ▁current ▁agreement ▁on ▁navigation ▁dates ▁from ▁ 1 9 9 2 . ▁ ▁Pol l ution ▁Pol l ution ▁has ▁long ▁been ▁a ▁problem ▁in ▁Lake ▁L ug ano . ▁In ▁the ▁ 1 9 6 0 s ▁and ▁ 1 9 7 0 s ▁it ▁was ▁officially ▁forb idden ▁to ▁bat he ▁in ▁the ▁lake . ▁Despite ▁the ▁continued ▁introduction ▁of ▁se w age ▁treatment ▁plants ▁such ▁as ▁in ▁Gand ria , ▁factors ▁such ▁as ▁lake ▁ret ention ▁time ▁and ▁lack ▁of