SEASONAL ABUNDANCE, COMPOSITION, AND PRODUCTIVITY OF 

 THE LITTORAL FISH ASSEMBLAGE IN UPPER NEWPORT BAY, 



CALIFORNIA 



Larry G. Allen 1 



ABSTRACT 



This study was designed to characterize the littoral fish populations by 1) composition and principal 

 species, 2) diversity and seasonal dynamics, 3) productivity, and 4 ) important environmental factors. 



Monthly samples (January 1978 to January 1979) obtained with four quantitative sampling 

 methods at three stations in upper Newport Bay yielded 55,561 fishes from 32 species which 

 weighed 103.5 kg. The top five species made up over 98% of the total number of individuals. One 

 species, Aikerinops affix is, predominated in numbers (76.7% of all fishes) and biomass (79.8%). This 

 dominance was reflected in the low overall H' diversity values for numbers (H' N = 0.89) and bio- 

 mass (H'h = 0.84). Number of species, number of individuals, and biomass were greatest during the 

 spring and summer. 



Quantitative clustering of species based on individual samples revealed five species groups which 

 reflected both microhabitat and seasonal differences in the littoral ichthyofauna. Species Group I 

 was made up of five resident species— A. affinis, Fund ul us parvipinnis, Clevelandia ios, Gillichthys 

 mirabilis, and Gambusia affinis. Species Groups II-VI were composed of summer and winter 

 periodics and rare species. 



The mean annual production (9.35 gdry weight/ m 2 determined by the Ricker production model) 

 of the littoral zone fishes was among the highestof reported values for comparable studies. This high 

 annual production was mainly the result of the rapid growth of large numbers of juveniles that 

 utilized the littoral zone as a nursery ground. Young-o{-the-yea.r Atherinops affinis contributed 85% 

 of this total production. 



Canonical correlation analysis indicated that temperature and salinity together may influence 

 littoral fish abundance. These two abiotic factors accounted for 83% of the variation in the abun- 

 dances of individual species. Emigration from the littoral zone, therefore, seems to be cued by 

 seasonal fluctuations in temperature and salinity. I propose that this offshore movement forms an 

 important energy link between the highly productive littoral zone and local, nearshore marine 

 environment. 



Semienclosed bays and estuaries are among the 

 most productive areas on Earth, ranking with 

 oceanic regions of upwelling, African savannas, 

 coral reefs, and kelp beds (Haedrich and Hall 

 1976) in terms of animal tissue produced per 

 year. Bays and estuaries harbor large stocks of 

 nearshore fishes and are important feeding and 

 nursery grounds for many species of fish, in- 

 cluding commercially important ones. However, 

 the high productivity of fishes is accompanied by 

 low diversity (Allen and Horn 1975) which prob- 

 ably reflects the stressful ecological conditions in 

 bays and estuaries and the high physiological 

 cost of adaptation to them (Haedrich and Hall 

 1976). The few studies that have dealt with pro- 



1 Department of Biological Sciences, University of Southern 

 California, Los Angeles, Calif.: present address: Department 

 of Biologv. California State University, Northridge, CA 

 91330. 



ductivity in estuarine fishes were summarized 

 by Wiley et al. (1972) and Adams (1976b). 



Utilization of temperate embayments by juve- 

 nile and adult fishes is markedly seasonal with 

 high abundances corresponding to the warmer, 

 highly productive months of spring through 

 autumn. Seasonal species typically spend one 

 spring-autumn period in the shallows of a bay 

 growing at an accelerated rate in the warm, 

 highly productive waters (Cronin and Mansueti 

 1971). 



Most studies to date dealing with composition 

 and temporal changes of bay-estuarine fish 

 populations have been conducted on the Gulf of 

 Mexico and Atlantic coasts of the United States 

 where estuaries are larger and more numerous 

 than those on the Pacific coast (e.g., Bechtel and 

 Copeland 1970; Dahlberg and Odum 1970; Der- 

 ickson and Price 1973; McErlean et al. 1973; 

 Oviatt and Nixon 1973; Recksiek and McCleave 



Manuscript accepted March 1982. 



FISHERY BULLETIN: VOL. 80, NO. 4, 1982. 



769 



