ALLEN: LITTORAL FISH ASSEMBLAOE 



and Allen 1981) obtained a bimonthly range for 

 numbers of 0.48-2.17 (overall 1 .05) when the deep- 

 er channel areas were also sampled. The rela- 

 tively wide range of H'\ values in all of the above 

 studies reflects the differential utilization of 

 these embayments by fishes on a seasonal basis. 

 At the same time, the low overall diversity re- 

 flects dominance both in numbers and biomass 

 by a few species. The seasonal usage has the 

 effect of increasing annual diversity, although 

 only one or two species dominate numerically at 

 any one time. The H' values for biomass (H'n 

 range 0.23-1.55; overall 0.84) were fairly close to 

 those for numbers and, again, mainly reflected 

 the dominance of A. affinis (~80%). In all, 26 of 

 the 32 reported species had young-of-the-year 

 fishes, making up a significant portion of their 

 populations. Fluctuations in juvenile population 

 levels had a substantial effect on the littoral fish 

 populations. Juvenile recruitment plus the im- 

 migration of adult fishes presumably for repro- 

 duction or for exploitation of high productivity in 

 warmer months were the principal causes for 

 seasonal changes in the ichthyofauna. These ac- 

 tivities reflect the widely recognized function of 

 bay-estuarine environments as spawning and 

 nursery grounds (Haedrich and Hall 1976). 



The general pattern of increased number of 

 species and numbers of individuals during the 

 late spring through fall period in upper Newport 

 Bay has been observed in many other studies of 

 temperate bay-estuarine fishes (e.g., Pearcy and 

 Richards 1962; Dahlberg and Odum 1970; Allen 

 and Horn 1975; Adams 1976a). Several studies of 

 estuarine fish populations have, in addition, de- 

 tected summer depressions in abundance be- 

 tween peaks in spring and fall in other estuaries 

 (Livingston 1976; Horn 1980) and in lower New- 

 port Bay (Allen 1976). 



Studies of subtropical estuarine fish popula- 

 tions have shown a trend in seasonal abundances 

 that is 6 mo out of phase with the above observa- 

 tions. Fish abundances were highest during the 

 winter months (November-March) in the Hui- 

 zache-Caimanero Lagoon of Mexico due to 

 increases in members of both demersal and pe- 

 lagic fishes (Amezcua-Linares 1977; Warburton 

 1978). This coastal lagoon system is subject to a 

 narrower range of temperatures over the year 

 (18.3°-27.9°C) than most temperate systems. 

 However, the Mexican system undergoes wide 

 variation in salinity, especially during the rainy 

 season from July to October (see section Influ- 

 ence of Abiotic Factors). 



Species Associations 



Species groupings were subject to strong sea- 

 sonal influence and bore a striking resemblance 

 to the classification scheme of Atlantic nearshore 

 fish communities proposed by Tyler (1971). Ac- 

 cording to Tyler's classification the Atlantic 

 nearshore fish communities can be divided into 

 regular and periodic components. Periodic com- 

 ponents can be winter seasonals, summer season- 

 al, or occasionals. The upper Newport Bay fish 

 assemblage had regulars (group I) and periodics 

 (groups II-V). The "anchovy" group (II), the 

 "goby" group (III), and the " Engraulis-Hypsop- 

 setta" group (IV) were all summer seasonals. 

 Group V had both winter seasonals in Mugil 

 cephalus and Lepomis macrochirus and summer 

 seasonals in Lepomis cyaneilus and Leuresthes 

 tenuis. The latter group, however, could best be 

 characterized by the affinity of its components to 

 lower salinities rather than to a particular time 

 of year. The occasional component was repre- 

 sented by the 12 species of group VI which also 

 occurred in the summer. Thus Tyler's classifi- 

 cation may have a broader application than he 

 originally proposed, and perhaps holds true for 

 many estuarine ichthyofaunas. 



Species Densities and Productivity 



Density estimates for some species of littoral 

 fishes are particularly difficult to obtain. Such 

 species include small, burrow-inhabiting fishes 

 of the family Gobiidae and other small benthic 

 fishes such as killifishes, flatfishes, and sculpins 

 which escape under a seine or through the mesh 

 of various nets. This study attempted to obtain 

 density values for all littoral fishes, especially for 

 the elusive species listed above. By setting up the 

 procedure for choosing the "best estimate" of 

 density from among four different sampling 

 methods, actual densities of the species have 

 been more closely approximated. 



If the biomass density of Atkerinops af finis for 

 the entire study is calculated by dividing its total 

 biomass by the total area of coverage by all four 

 sampling gears, a biomass density of 3.3 g/m 2 (or 

 about 0.83 g DW/m 2 ) is obtained. This density 

 value is lower than the estimate of 1.16 g DW/m 2 

 derived through the best estimate process (Table 

 6). In this particular case, most densities were 

 mean values of six bag seines which were very 

 effective (99%) at capturing A. affinis (Horn and 

 Allen footnote 2). Biomass density for the gobiid, 



785 



