bivalves being most numerous. The California Department of Fish and Game 

 planted some abalone, but all other groups of animals have been introduced 

 through natural means. 



8. Bryozoa . Of these marine invertebrates, which characteris- 

 tically form branched or mossy colonies, eight species have been identified. 

 They occur as encrusting forms with delicate structures, growing on hard 

 surfaces such as rocks or shells. 



9. Echinodermata . Brisby notes that the echinoderms are one of 

 the most noticeable forms of life generally found in the intertidal zone. 

 Of the five major classes, four are represented at Rincon Island, and of 

 these, 15 species have been identified. 



10. Chordata. These include the numerous kinds of fishes, birds, 

 and marine animals . Brisby lists five classes of chordates : the tunicates 

 or sea squirts; the chondrichthyes which include sharks and rays; the 

 osteichthyes, including the many kinds of fish; the aves or birds; and the 

 mammals. A total of 118 species of chordata have been identified. 



c. Biological Impact - In his assessment of the biological impact of 

 the island, Brisby notes that with its construction a new environment was 

 established with a great number of hard surfaces for the attachment of 

 various organisms. The placement of the large slabs of quarry rock and 

 tetrapods added positive components to the environment by providing crev- 

 ices and caves into which various animals could retreat for protection from 

 both currents and predators. The sand-silt bottom has an effect upon the 

 island, however, as turbid currents continually carry the benthic sediments 

 up onto the rock revetments to a height of about 6 to 10 feet. 



The position of the island, one-half-mile offshore, also allows a 

 varied environment in respect to exposure to the open ocean waves and 

 currents. This in turn provides for an environment which exposed zonation, 

 protected zonation, and intermediate stages, making possible a greater 

 diversity of life than is usually found in an area of this size. Nearly 

 all forms of life found on the offshore Channel Islands now exist on and 

 around Rincon Island. Of great importance in maintaining this diversity 

 is the fact that the island is closed to the general public and the various 

 organisms are given an opportunity to grow and develop undisturbed. 



The seaward side of the island is particularly rich in life. A rather 

 extensive kelp bed has developed, and the more than 1,000 tetrapods have 

 provided an optimum environment for the reproduction and rearing of numer- 

 ous organisms, especially many pelagic forms. The kelp bed on this part 

 of the island becomes quite luxuriant in the summer. Mussel beds, several 

 feet thick, have developed on the tetrapods with the myriad population of 

 organisms associated with these beds. The primary fish forms resident in 

 this section are the perches and blennies. This is also a primary roosting 

 ground for marine birds, with temporary populations of several hundred 

 brown pelicans, cormorants, and gulls observed regularly. 



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