Fecundity of the Acorn Barnacle Balanus Pacificus Pilsbry: A Fugitive Species1

The distribution of Balanus pacificus along the coasts of California and Baja California indicates that it probably is a fugitive species. This barnacle usually occurs on small ephemeral objects in the sand rather than in established many‐species communities on rock. It occurred in only 11% of the 94 rocky areas but in 83% of the 53 sandy areas examined. It is well suited for such an existence; when compared to other barnacles, it shows a high fecundity and an early age of maturity. It also breeds continuously throughout the year and is thus able to take advantage of suitable substrates as they become available.