TEMPORAL AND SPATIAL PATTERNS OF NEARSHORE 



DISTRIBUTION AND ABUNDANCE OF THE PELAGIC FISHES 



OFF SAN ONOFRE-OCEANSIDE, CALIFORNIA 



Larry G. Allen 1 and Edward E. DeMartini 2 



ABSTRACT 



The pelagic fishes off San Onofre-Oceanside, California, were sampled nearshore (within 0.5-3.0 km of 

 shore) during September 1979 to March 1981, using standardized lampara net gear. Sixty-two taxa were 

 collected in 643 net-hauls systematically partitioned among three depth strata during day and night periods. 

 Engraulis mordax dominated the catch and accounted for about 81% of all fishes. Seriphus politus, 

 Genyonemus lineatus, Peprilus simillimus, and one species complex (atherinid spp.), together with£. mordax, 

 made up >987r of the total numerical catch. Total catch per unit effort (CPUE) was greatest during the sum- 

 mer months (June-September), due mainly to the increased abundance of Engraulis mordax. The CPUE of 

 other common species fluctuated little throughout the year except for a general decline during October- 

 December because of the decreases in catches of Seriphus politus and Genyonemus lineatus. Four species 

 groups were defined by quantitative clustering. Species Group I contained the above five most abundant and 

 ubiquitous species. Groups II and III consisted of periodic species that occurred nearshore primarily during 

 warmer and cooler water months, respectively. Group IV was composed of nine species of relatively rare 

 bottom-oriented fishes. 



The most conspicuous pattern exhibited by the common species in the assemblage involved a marked shift 

 in depth over a diel period. Engraulis mordax, Seriphus politus, Genyonemus lineatus, and, to a lesser extent, 

 Peprilus simillimus schooled in shallow water (5-11 m depths) during the day and dispersed offshore of these 

 depths at night. Analysis of gut fullness during day and night suggested that Seriphus politus, and possibly 

 Genyonemus lineatus and Engraulis mordax, disperse at night in part to feed on nocturnally active prey. 



The marked depth and diel patterns of abundance that were observed could only be attributed in small part 

 to depth-specific differences in water clarity and diel differences in catch efficiency. 



Knowledge of pelagic fish assemblages that inhabit 

 the waters off California is limited to general ac- 

 counts from commercial catch records, larval fish 

 studies and surveys (reviewed in Lasker 1982), and 

 hydroacoustic surveys of adults (Mais 1974). These 

 sources have provided general information on com- 

 position, distribution, and behavior of the offshore 

 component of the pelagic ichthyofauna. This fauna is 

 heavily dominated in numbers and biomass by the 

 schooling clupeiform — northern anchovy, Engraulis 

 mordax — especially within 37 km of the coast be- 

 tween Santa Barbara and San Diego (Mais 1974). 

 Jack mackerel, TYachurus symmetricus; Pacific mack- 

 erel, Scomber japonicus; Pacific sardine, Sardinops 

 sagax; Pacific saury, Cololabis saira; and Pacific 

 hake, Merluccius productus, are also important com- 

 ponents of this fauna, although their relative abun- 

 dances are poorly known (Mais 1974). Information 

 on the relative abundances of pelagic fish stocks of 



1 Marine Science Institute, University of California, Santa Barbara, 

 Calif; present address: Department of Biology, California State 

 University, Northridge, CA 91330. 



''Marine Science Institute, University of California, Santa Barbara, 

 CA 93106. 



Manuscript accepted November 1982. 

 FISHERY BULLETIN: VOL. 81. NO. 3, 1983. 



nearshore (<3.0 km from shore) waters was limited 

 to a few unpublished reports prior to the initiation of 

 the present study. 



Little is known about the diel and seasonal 

 movements of fishes within the Southern California 

 Bight, although the diel activity patterns of some 

 fishes associated with kelp beds in the Bight have 

 been documented (Ebeling and Bray 1976; Hobson 

 and Chess 1976; Hobson et al. 1981). Several of 

 these species (queenfish, Seriphus politus; salema, 

 Xenistius ealiforniensis; walleye surfperch, Hyper- 

 prosopon argenteum) are known to make diel migra- 

 tions between kelp beds and nearshore pelagic and 

 other coastal (e.g., sandy surf zone) habitats (Hobson 

 and Chess 1976). 



This study is the first direct, systematic assessment 

 of the pelagic fish assemblage inhabiting nearshore 

 (<3 km) waters off southern California. The specific 

 purposes of this paper are to characterize this assem- 

 blage by 1) species composition, 2) major spatial and 

 temporal patterns of abundance and distribution, 3) 

 species associations, and 4) important environmen- 

 tal factors. 



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