▁in ▁l ago ons , ▁often ▁in ▁se agr ass ▁b eds , ▁and ▁the ▁adult s ▁are ▁found ▁in ▁clear ▁outer ▁l ago ons ▁and ▁sea ward ▁re ef s ▁up ▁to ▁a ▁depth ▁of ▁ 3 0   m . ▁They ▁feed ▁on ▁b enth ic ▁alg ae ▁and ▁live ▁cor als . ▁ ▁Ad ult ▁green ▁hum p head ▁par rot fish ▁may ▁ram ▁its ▁head ▁against ▁cor als ▁to ▁facil itate ▁feed ing . ▁Each ▁adult ▁fish ▁ing ests ▁over ▁five ▁tons ▁of ▁struct ural ▁re ef ▁carbon ates ▁per ▁year , ▁contrib uting ▁significantly ▁to ▁the ▁bio eros ion ▁of ▁re ef s . ▁The ▁fish ▁sle eps ▁among ▁cor als , ▁in ▁c aves ▁and ▁ship w re cks ▁at ▁night , ▁usually ▁in ▁large ▁groups . ▁ ▁Conserv ation ▁ ▁The ▁large ▁size , ▁slow ▁growth ▁and ▁school ing ▁behavior ▁of ▁this ▁species ▁mean ▁it ▁is ▁sus cept ible ▁to ▁over f ishing . ▁This ▁species ▁is ▁highly ▁sought ▁after ▁by ▁fish erm en ▁throughout ▁its ▁range , ▁and ▁it ▁has ▁decl ined ▁from ▁over har vest ing . ▁Spe ar fish ers ▁and ▁net ters ▁target ▁large ▁groups ▁as ▁they ▁sleep ▁at ▁night . ▁The ▁species ▁was ▁identified ▁as ▁a ▁Species ▁of ▁Conc ern ▁by ▁NO AA / N M FS ▁in ▁ 2 0 0 4 , ▁meaning ▁that ▁the ▁species ▁is ▁thought ▁to ▁be ▁threatened , ▁but ▁ins u fficient ▁data ▁are ▁available ▁to ▁justify ▁a ▁listing ▁under ▁the ▁End anger ed ▁Species