TEGNER ET AL.: BIOLOGY AND MANAGEMENT OF RED ABALONES 



by animals of commercial legal size or larger (Fig. 

 2, Table 3) suggests that fishing pressure is very in- 

 tense and that fishermen are searching for cryptic 

 abalones. Thirty-five percent of the total number of 

 abalones in the destruct quadrats were emergent 

 (yearly range: 25-50%). 



Total, sport-legal, and commercial-legal densities 

 of emergent abalones were calculated from the com- 

 bined results of the destruct and nondestructively 

 sampled quadrats. Again inspection of the 95% con- 

 fidence intervals around the yearly means suggests 

 that there were no significant changes in density 

 over the five years studied despite the fourfold 

 larger sample sizes and correspondingly smaller 

 standard errors. The mean density of the total num- 

 ber of abalones from these quadrats was 30% of the 

 mean total density determined from the destruct 

 quadrats, comparable to the 35% of the destruct 

 quadrat animals which were emergent. The density 

 of emergent, commercial legal-sized animals ranged 

 from one to three per 1,000 m-, again suggesting 

 that Johnsons Lee is intensely searched. In contrast, 

 the density of emergent sport legal-sized red aba- 

 lones ranged from 10 to 23 per 1,000 m-. The size- 

 frequency distribution of emergent abalones from 

 both the destruct and nondestruct quadrats is illus- 

 trated in Figure 4. 



The high variance in the density estimates can be 

 ascribed to two factors. First, a substantial propor- 

 tion of the rocky substrate was a very flat, pave- 



ment-like surface often covered with a thin layer of 

 silt. This surface supports Macrocystis and rarely 

 large red abalones, but not small or intermediate- 

 sized animals. Second, the distribution of abalones 

 at Johnsons Lee was highly contagious in all years 

 sampled. The variance to mean ratio was calculated 

 as an index of dispersion and the significance of 

 departures from unity tested with x", and for large 

 samples (w > 31), with the normal variable (Elliot 

 1971). In each case the x" value was highly signifi- 

 cant (P < 0.005). In 1979, for example, 63% of the 

 total number of abalones found in the destruct 

 samples were in one quadrat. 



Habitat Considerations 



Cox (1962) reported that abalones prefer areas 



where there is sand, and Shepherd (1973) recog- 

 nized the importance of sand patches and channels 

 as areas for the movement and accumulation of 

 algal drift. A x~ analysis was conducted to deter- 

 mine whether red abalones were concentrated 

 in the rock/sand areas or uniformly distributed 

 between the rock and rock/sand habitat types 

 (Table 4). On the scale of the 15 m^ quadrats, red 

 abalones, both emergent and nonemergent, did 

 not show a preference for either habitat type. In con- 

 trast, both red and purple sea urchins were found 

 in habitat classified as rock more often than 

 expected. 



1978-1982 

 N = 532 



UJ Q_ 



35 65 95 125 155 185 215 

 SIZE (mm) 



Figure 4.— Size-frequency distribution of emergent red abalones 

 found in the destruct and nondestruct quadrats. 1978-82. The data 

 were scaled for differences in effort between years. The dashed lines 

 indicate sport (178 mm) and commercial (197 mm) legal minimum 

 sizes. 



323 



