EBELING ET AL.: ANNUAL VARIABILITY OF REEF FISH 



Table 7. — Annual variation of estimated density (individuals per hectare) of common kelp-bed fish species at mainland and Santa 

 Cruz Island study sites off Santa Barbara, southern California. Variance \ n, the variance of square roots of yearly densities, 

 measures yearly variability discounting effects of means; R at bottom of table, the mean of log fl's — the average difference in log^^ 

 density for the species array between two successive years, measures net change in the array; AV, the variance of logic's, measures 

 the scope of change. Between-year totals yield these statistics for an array of all 32 log R's (See text and Wolda 1978). A dash ( — ) 

 indicates that the number was too small for analysis. 



(Table 7). In general, mean log i?'s (Table 7, R), 

 which measure net annual change between 

 species arrays, differed significantly within 

 (^tests,P<0.01), but not between (P>0.05) sites. 

 This further indicated that species abundances 

 varied concordantly on both sides of the Channel. 

 For the mainland site, R for 197 1-72 was positive, 

 indicating net increases in most species between 

 these years (Table 7) as total fish counts increased 

 significantly both in canopy and bottom habitats 

 (Table 3); was negative for 1972-73 as numbers 

 decreased in both habitats; and was zero for 1973- 

 74 as a decrease in total canopy numbers offset an 

 increase in bottom numbers. Net annual changes 

 at the island site were somewhat less marked (Ta- 

 ble 7), and numbers offish differed significantly 

 between 1972 and 1973 only (Table 3). In general, 

 variances of logo's (Table 7, AV), which measure 

 the scops of annual differences between species 

 arrays, did not differ significantly either within or 

 between sites (F-tests, P>0.1). However, the 

 within-site differences were more marked, which 

 is consistent with the concordance of annual 

 trends of the mainland and island sites. 



Much of the yearly variation in fish abundance 

 was due to fluctuations in species that aggregate 

 in the kelp canopy, especially midwater plankti- 



vores (Table 7). The average among-year variance 

 of transformed numbers of three abundant plank- 

 tivores (B. frenatus, Chromis punctipinnis, and S. 

 mystinus) was relatively large (145.4, n = 5); that 

 for abundant species whose vertical distributions 

 are somewhat broader (Paralabrax clathratus, G. 

 nigricans, S. serranoides, and O. californica) was 

 substantially less (13.4, n = 8); while that for 

 abundant demersal species (E. jacksoni, Hyp- 

 sypops rubicundus, and Pimelometopon pul- 

 chrum) was smaller still (5.4, n = 5). 



Yearly differences were loosely related to 

 underwater visibility, water temperature, and, 

 perhaps, to kelp density in the canopy. Water was 

 relatively clear and warm during September 1972 

 (Table 6) when counts of individuals and of species 

 were high. Furthermore, water was turbid and 

 cool at the island site during 1973 when counts 

 were low. However, at the mainland site in 1973, 

 where no such conditions prevailed (Table 6), bot- 

 tom counts were also low (Table 3). Kelp density 

 seemed to affect canopy counts at the mainland 

 site, where lower scores for kelp density in 1974 

 (Table 5) coincided with lower counts offish in the 

 canopy (Table 3). 



In sum, variation in composition (order of rela- 

 tive or ranked species abundances) was less 



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