Biology/Natural History: Fatty acid composition indicates that small individuals eat mainly detritus while larger individuals feed mainly on diatoms.

This subtidal barnacle has 6 plates and the rostrum overlaps the adjacent plates. Its terga are drawn out into a beak (photo). The outside of the plates are fairly smooth or with shallow longitudinal striations, not much eroded. The base is well calcified. The tubes within the wall plates do not have transverse septa. The overlapping portions of the plates are usually glossy (photo). Usually less than 3 cm diameter but may be up to 5 cm. In my experience this barnacle is usually as tall or taller than wide.

Geographical Range: (At least along our Pacific Coast and off Japan)

How to Distinguish from Similar Species: Balanus balanus has septae in the tubes of the wall plates. Balanus nubilus grows much larger, usually has heavily eroded plates, has longer beaks, and appears bright orange-yellow when it opens. Semibalanus cariosus has thatchlike projections on the outside of the plates. Balanus crenatus looks superficially similar but has no beaks.

Depth range based on 6 specimens in 4 taxa.
Water temperature and chemistry ranges based on 2 samples.

Environmental ranges
  Depth range (m): 31 - 88
  Temperature range (°C): -0.055 - 0.686
  Nitrate (umol/L): 4.279 - 7.786
  Salinity (PPS): 32.463 - 32.770
  Oxygen (ml/l): 6.159 - 7.167
  Phosphate (umol/l): 1.050 - 1.173
  Silicate (umol/l): 18.169 - 27.397

Graphical representation

Depth range (m): 31 - 88

Temperature range (°C): -0.055 - 0.686

Nitrate (umol/L): 4.279 - 7.786

Salinity (PPS): 32.463 - 32.770

Oxygen (ml/l): 6.159 - 7.167

Phosphate (umol/l): 1.050 - 1.173

Silicate (umol/l): 18.169 - 27.397
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Depth Range: (In my experience this barnacle is found mainly quite deep)--below normal SCUBA depths.