Analysls of Denslty and Distribution Patterns In Chrysophrys auratus (Pisces: Sparidae) Within a Reef Environment: An Experimental Approach

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Abstract
Density estimates for the fish C. auratus (Forster) were obtained within a shallow subtidal reef system in northeastern New Zealand by transect counts. The mean density in 6 reef areas during Dec. 1978 varied from 2.8-139 individuals [ind.] 500 m-2. The time of day at which counts were made did not influence estimates of density. A further series of replicated counts in 7 reef areas from Dec. 1978-April 1980 revealed large seasonal differences in density. These differences resulted from a summer influx of 1st yr (0+) C. auratus into the reef system. Peak densities of 0+ individuals dropped to less than 5 ind. 500 m-2. This influx of 0+ individuals was recorded in both 1979 and 1980. Older individuals showed no seasonal trends in density. During summer a positive exponential relationship was detected between the percentage cover of the turfing alga Corallina officinalis and the density of 0+ C. auratus (n = 11, r = 0.79). These fish fed in the Corallina turf. Experimental removal of replicated 25 m-2 areas of C. officionalis resulted in a 50-70% decline in fish feeding rates. At adjacent uncleared control sites there was no significant change in feeding rate, but aggressive interactions between 0+ fish showed an increase ranging from 58-217%. These results suggest that 0+ C. auratus defend local feeding sites over areas of Corallina turf.