Sturgeons are large fish. The fact that the game does not consider them predatory does not stop them from happily biting off a few chunks of your dwarves, given opportunity. They can seriously wound or even kill a trained war dog, though that dog can sometimes kill them. They will scare away civilian dwarves. They may also be able to kill a low level dwarf.
They are also extremely dangerous in adventure mode, where they can easily chew your head off in mere seconds. If you do find yourself attacked by a sturgeon (for whatever reason), you should simply run away, as they only attack creatures adjacent to them.
[CREATURE:FISH_STURGEON] [NAME:sturgeon:sturgeons:sturgeon] [TILE:224][COLOR:6:0:0] [LARGE_ROAMING] [AQUATIC][UNDERSWIM][IMMOBILE_LAND] [MODVALUE:3] [GENPOWER:3] [PREFSTRING:bony scutes] [ALL_ACTIVE] [POPULATION_NUMBER:15:30] [BENIGN][NATURAL] [PETVALUE:300] [BODY:BASIC_2PARTBODY:BASIC_HEAD:SIDE_FINS:DORSAL_FIN:TAIL:2EYES:HEART:GUTS:ORGANS:NECK:SPINE:BRAIN:MOUTH] [ATTACK:MAIN:BYTYPE:MOUTH:bite:bites:1:6:GORE][ATTACKFLAG_CANLATCH] [ATTACK:SECOND:BYTOKEN:TAIL:slap:slaps:1:2:BLUDGEON][ATTACKFLAG_WITH] [SIZE:10] [MAXAGE:20:30] [NO_DRINK] [CHILD:1][CHILDNAME:sturgeon fry:sturgeon fry] [FAT:5] [BIOME:OCEAN_ARCTIC] [BIOME:OCEAN_TEMPERATE] [BIOME:RIVER_TEMPERATE_FRESHWATER] [BIOME:RIVER_TEMPERATE_BRACKISHWATER] [BIOME:RIVER_TEMPERATE_SALTWATER] [STANDARD_FLESH] [HOMEOTHERM:10067] [SWIMS_INNATE][SWIM_SPEED:500] [MUNDANE]