generally restricted to the deeper waters on the other three sides. On 

 the east side, a layer of silt varying in thickness from a few milli- 

 meters to over a centimeter covered most rock surfaces up to the lower 

 intertidal. This silt precludes growth of some encrusting organisms 

 (especially Lithothamnium complex), while others (e.g., Veleroa com- 

 plex) seem tolerant of it. 



5. Quantitative Characteristics of Major Species Associations . 



The following average biomass values were developed for common 

 attached biota not amenable to routine quantitative removal from the 

 substrate: 



Dodecaceria fewkesi (animals only, no tubes) : 465 grams per 



0.25 square meter 

 Lithothamnium complex: 783 grams per 0.25 square meter 

 Serpulorbis sguamigerus (animals only, no shells): 1.9 grams 



per individual 

 Veleroa complex: 242 grams per 0.25 square meter 

 Corynactis californica: 190 grams per 0.25 square meter 



When the 250 quantitative quadrats were grouped according to the 

 preliminary association in which the quadrat was placed and the side 

 of the island sampled, 26 groups or "subareas" resulted (see App. D, 

 Table D-1). The designation of each of the 26 subareas in Table D-1 

 corresponds to the numerical association designations in Figures C-3 

 to C-6. For example, the data in Table D-1 for south-side association 

 5, refer to the macrophytic algae association on the south side only. 

 Data for this association in other areas of the island are found under 

 correspondingly different designations. 



For all species encountered in each of the 26 subareas, the fol- 

 lowing summary statistics are tabulated in Tables Dl and D-2: fre- 

 quency of occurrence (ratio of occupied quadrats to total number of 

 quadrats examined in the subarea; mean abundance per quadrat (numer- 

 ical or percent coverage) ; 95-percent confidence limits for mean 

 abundance; and average weight per individual (or per 100-square 

 centimeter coverage for species with densities estimated as percent 

 coverage). Multiplication of the value for mean density by the aver- 

 age weight value yields an estimate of biomass for any species in any 

 of the 26 groupings. Reliability of this estimate will be best for 

 common species whose densities are relatively uniform from one 

 quadrat to the next, as indicated by relatively narrow confidence 

 limits for the mean. Table D-3 contains information on areas covered 

 by each of the 26 subareas which were subjected to statistical 

 analysis. 



The resulting biomass data are useful in characterizing and com- 

 paring the major species associations of Rincon Island. However, the 



