Pacific Acorn Barnacle

At a glance

Pacific Acorn Barnacle (Balanus glandula) is a barnacle present across the CatchRules coverage area but without species-specific bag, size, or season rules tracked in our regulatory dataset.

Confirmed by 4,215 research-grade iNaturalist observations, with British Columbia, California, and Washington the top jurisdictions by observation count.

Notable details

• Pacific Acorn Barnacles are among the most abundant intertidal invertebrates on the U.S. West Coast.
• Barnacles have the longest penis relative to body size of any known animal — up to 8 times their body length.
• During low tide, they seal their shell plates tightly to retain moisture and survive hours of air exposure.
• They are simultaneous hermaphrodites, producing both eggs and sperm at the same time.
• Larvae cement themselves permanently to rock within hours of choosing a settlement site.

Where Pacific Acorn Barnacle are seen

• British Columbia1,678 iNat obs
• California1,634 iNat obs
• Washington530 iNat obs
• Oregon270 iNat obs
• Alaska103 iNat obs

Background

Acorn barnacles (Balanus glandula) are one of the most common barnacle species on the Pacific coast of North America, distributed from the U.S. state of Alaska to Bahía de San Quintín near San Quintín, Baja California. They are commonly found in intertidal waters on mussels, rocks and pier pilings.

Background excerpt adapted from Wikipedia's Pacific Acorn Barnacle article (CC BY-SA). Visit Wikipedia for the full entry.

Other barnacles on CatchRules

• Northern Acorn BarnacleSemibalanus balanoides