Fucus distichus or rockweed is a species of brown alga in the family Fucaceae to be found in the intertidal zones of rocky seashores in the Northern Hemisphere, mostly in rock pools.

[1] Reproduction is seasonal, and receptacles start being formed in late autumn in response to short days.

It is thought that self-fertilisation often occurs in this species and once a zygote is formed it can only be dispersed over a limited distance.

[4] A study was undertaken to see what factors influenced natural gamete release and the rate of fertilisation success in Fucus distichus.

[7] It was found that the release and settlement of eggs and zygotes occurred during daytime low tide periods, particularly when these fell between 10am and 2pm.

Its presence increases species richness as it forms canopies in the mid to high intertidal zone that provide protection, shelter and food for a variety of small invertebrates including many gastropods and crustaceans.