The fragile urchin is found in the eastern Pacific from Vancouver Island, British Columbia to Baja California in depths of 26 to 689 fm on relative flat bottom of fine sands to clayey silt. Research trawl have found the highest availability in depths from 97 to 258 fm. Their distribution may be clumped. The sexes of fragile urchins are separate and spawning takes place by broadcasting the eggs and sperm in the water.
Male gonads are a creamy-white color and yellowish in females.
The relative mass of gonads in a fragile urchin is less than shallow water urchins. Another researcher suggests there may be two spawning seasons a year - a second season in late summer. The pelagic larval period may be up to 36 weeks juvenile urchins will then settle to the bottom. Food and Growth Fragile urchins are most likely bottom grazer, feeding on microscopic organisms and organic debris. The smallest specimen from trawl samples measured 8 mm, test diameter, the largest was 93 mm.