FISHERY BULLETIN; VOL. 78, NO. 2 



living in humid, climatically stable and more pre- 

 dictable areas, but were significantly less than 

 most values (0.12-0.64, averaging 0.34) for ar- 

 thropods living in dry, climatically unstable envi- 

 ronments (Wolda 1978: table 2). Values of AV 

 (0.17, 0.20) that we calculated from annual sight 

 transects of reef fishes taken off central California 

 by Miller and Geibel (1973) and Burge and Schultz 

 (see footnote 6) exceeded our values, but not sig- 

 nificantly so. But our AV's were significantly less 

 than the value (0.55) that we calculated from 

 Livingston's ( 1976) trawl samples of fish from a 

 Florida estuary during two successive winters (F- 

 tests of variance ratios, P<0.01). Thus, annual 

 variation in species abundances of our fish as- 

 semblages may be more typical of communities in 

 relatively stable environments than of those from 

 highly variable environments. 



Climatic and other environmental anomalies 

 may contribute to annual variation. Peak fish 

 abundance in 1972 occurred in relatively clear and 

 warm water, which may stimulate fish to be more 

 active (Quast 1968a, b, c; Larson 1977), and 

 perhaps more easily photographed. The summer 

 and fall of 1972 followed a relatively calm winter 

 of light rainfall (Harger 1979: append. B), and was 

 a favorable period for growth of small benthic 

 algae and associated animals, which are impor- 

 tant forage for surfperches and other microcarni- 

 vores. On the other hand, poor visibility may have 

 caused abrupt decreases in counts of Chromis 

 punctipinnis at the island site in 1973. An obliga- 

 tory daytime planktivore (Bray 1978), this species 

 may seek bottom shelter when water is turbid, 

 (jlenerally, midwater planktivores were more vari- 

 able in numbers than other species. Decreased 

 kelp cover at the mainland site in 1974 probably 

 drove some fish bottomward, but not necessarily 

 out of view; an aggregate decrease of eight indi- 

 viduals per canopy transect of C. punctipinnis, 

 Paralabrax clathratus, and O. californica accom- 

 panied a corresponding increase of five per bottom 

 transect. 



However, less obvious factors may be more im- 

 portant, because other periods of clear and warm 

 water produced no such peak abundances. Time 

 lags in responses of fish populations to environ- 

 mental change preclude simple explanations of 

 annual variation. Lags between bumper births 

 and subsequent adult recruitment may cause 

 populations to overshoot their environmental car- 

 rying capacities (Hutchinson 1978). Alterna- 

 tively, fixed spawning seasons coupled with an 



unpredictable cycle in food production may limit 

 recruits independently of the carrying capacity of 

 the environment for adults (Cushing 1969). From 

 bottom-trawl catches, Mearns'^ concluded that re- 

 cruitment of juvenile nearshore fishes occurs over 

 relatively short periods off southern California 

 and may vary markedly in success among species 

 from one year to the next. Larson (1977) found that 

 counts ofS. carnatus andS. chrysomelas decreased 

 significantly at several depths in an area near the 

 island site during 1973-76. This decrease may 

 have been the result of sparse juvenile settlement 

 observed in 1974-75. 



Migration and predation may play a role, espe- 

 cially at the mainland site, a semi-isolated 

 offshore reef; e.g., kelp perch, which are canopy 

 specialists, occurred sporadically and sparsely 

 there. Kelp cover has varied considerably over the 

 years. But even though cover may vary at other 

 places as well, the distance of this reef from exten- 

 sive kelp beds inshore may have inhibited kelp- 

 perch recolonization after periods of canopy loss. 

 Several natural predators eat reef fishes, but we 

 do not know if the rate varies from year to year. 

 During the day, harbor seals and sea lions forage 

 at both sites. Predatory fish such as kelp bass may 

 eat relatively more young of species such as 

 surfperches that do not hide in the reef itself, dur- 

 ing periods when plant cover is sparse. At night, 

 larger individuals of such prey fish may be par- 

 ticularly vulnerable to large Pacific electric ray, 

 Torpedo californica, which invade the reef then 

 (Bray and Hixon 1978). Love (1978) concluded 

 that olive rockfish, which grow slowly and seldom 

 move between reefs, are decimated chronically by 

 overfishing. Although kelp bass are equally 

 exploited, adult replacements apparently move in 

 to restore a portion of a contiguous population 

 (Quast 1968d). 



It is noteworthy that the constancy or "stability" 

 in species composition of our fish assemblages was 

 roughly correlated with species diversity. Canopy 

 assemblages were relatively simple, with many 

 individuals distributed unevenly among a few 

 species. They were less constant in composition 

 than the bottom assemblages, which were charac- 

 terized by more species and more even distribution 

 of individuals among species. Also, the island bot- 

 tom assemblage, which was the more diverse 



'^Meams, A. J. 1977. Abundance of bottom fish off Orange 

 County. In Coastal water research project, annual report 1977, 

 p. 133-142. Southern California Coastal Water Research Project, 

 646 W. Pacific Coast Highway, Long Beach, CA 90806. 



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